CHIANTI

An Atomic Database for Spectroscopic Diagnostics of Astrophysical Plasmas

USER GUIDE - Version 5.0 - 18 August 2005

Written by Giulio Del Zanna

with contributions from Peter Young and the team members.

Contents

1  What's new in Version 5.0

• Inclusion of ionization and recombination effects in level population calculation     - see Sect. 8.6, Sect. 5.1.1.
• Photoexcitation from any user-provided radiation field     - see Sect. 8.5 and Sect. 9.7
• Non-maxwellian distribution of electron velocities     - see Sect. 8.3 and Sect. 9.8
• New data for

  • Fe IX, Fe X, Fe XII, Fe XV (EUV)
  • Fe XVII to Fe XXIV (X-rays)
  • n=3 to n=3 transitions for N-like and O-like ions
  • new ions (P XIV, XV; Cl II, X, XI, XII, XVII; K V, XVII, XIX; Ca VII, VIII; Co XX; Zn XXIII)
• The software has been improved and speeded. Fixed various minor bugs.
• A few new useful routines, in particular:

  which_line
  pop_processes
  
  

  (see the example section).
• Added keV option to calculate/plot spectra in energy units.

The changes introduced to speed the calculations were made necessary by the increasingly larger atomic models now available in CHIANTI, that made the running time of the software of the previous version too long.

The software is backward-compatible, i.e. can be used together with previous versions of the database.

2  What was new in Version 4.1

-Added detailed descriptions of the data file contents.

-Replaced the continuum plot, that was created with the corrupted version of the itoh.dat file.

-Corrected instructions for installation within Windows.

3  What was new in Version 4.0

This document describes the general characteristics of the new Version 4.0 of the CHIANTI package (database and IDL procedures).

A considerable number of new features, both in the database and the software, have been added (see Young et al., 2003). We have tried to keep a distinction between the previous and the new features in this document.

Users of previous versions, please NOTICE:

1. The procedures to install CHIANTI as a stand-alone package have changed in small but important ways.
2. New kinds of files (.fblvl and .psplups) are now being distributed and the format of the .splups files has changed.
3. The entire previous software has been rewritten. There are a few minor changes in the way the procedures are called.
4. New software has been written.
5. The CHIANTI routines now use SolarSoft routines.

The main new features described in this guide are

• New CHIANTI distribution and structure     - see Sect. 7
• Photoexcitation and Stimulated Emission     - see Sect. 8.4
• New software     - see Sect. 6.1 and App. A
• New continuum calculations     - see Sect. 8.7
• Incorporating proton rates into CHIANTI     - see App. B
• Incorporating 9 point spline fits into CHIANTI     - see App. C

Backward compatibility has been assured for almost all cases. In practice, previous users of CHIANTI will be able to use the new V.4 software as before, with just minor changes. On the other hand, software versions prior to 4 are not compatible with the v.4 database.

This document replaces the previous CHIANTI guide (Version 1.0).

4  Introduction

CHIANTI is a collaborative project involving researchers based at the Naval Research Laboratory (NRL, Washington DC, USA), Rutherford Appleton Laboratory (RAL, UK), the University College London (UCL, UK), the University of Cambridge (UK), the George Mason Univerity (GMU, USA) and the University of Florence (Italy).

4.1  What is CHIANTI

The CHIANTI package consists of a critically evaluated set of atomic data (energy levels, wavelengths, radiative transition probabilities and excitation data) for a large number of ions of astrophysical interest. It also includes a number of ancillary data and a suite of Interactive Data Language (IDL) programs to calculate optically thin synthetic spectra and to perform spectral analysis and plasma diagnostics.

Plasma emission codes have long been used to study UV and X-ray spectral lines emitted from solar or stellar atmospheres. A comparison of the theoretical line intensities with the observed intensities allows a determination of the physical parameters for the plasma (cf Mason and Monsignori Fossi, 1994 and Del Zanna, Landini and Mason, 2002).

It is very important, now that high accuracy atomic data are available, to improve and keep up-to-date the plasma codes.

The CHIANTI database has been used extensively by the astrophysical and solar communities to analyse emission line spectra from astrophysical sources.

The CHIANTI package is freely available at one of the CHIANTI homepages:

• RAL, UK: http://www.chianti.rl.ac.uk/
• NRL, USA: http://wwwsolar.nrl.navy.mil/chianti.html
• UCL, UK: http://www.mssl.ucl.ac.uk/www_solar/chianti/
• DAMTP, UK: http://www.damtp.cam.ac.uk/user/astro/chianti/chianti.html
• GMU, USA: http:
• Univ. of Florence, Italy: http://www.arcetri.astro.it/science/chianti/chianti.html

or at

• SolarSoft, a programming and data analysis environment for the solar physics community. http://www.lmsal.com/solarsoft/

4.2  Important caveats and limitations

As with any atomic data package, CHIANTI has been developed to suite some specific applications in astrophysics, and users should read the CHIANTI papers and the documentation to find out the ranges of applicability of the package.

Currently, some of the main assumptions and limitations of the data and programs are:

• Level excitations occur via collisional excitation by electrons and protons, and photoexcitation from black-body or user-defined radiation fields.
• Electrons and protons have Maxwellian distribution functions. Indeed CHIANTI data include Maxwellian-averaged electron and proton collision strengths. However, it is possible to study the effects of particle distributions that are linear combinations of Maxwellians of different temperatures.
• Electrons and protons have the same temperature.
• The plasma ionization is dominated by collisions (i.e. no photo-ionization is included).
• Atomic processes affecting the ionisation state of an element can be separated from those affecting the level balance within an ion.

  A correction to the level populations due to ionization and recombination is included, but it is only valid up to densities above which metastable level populations begin to be non-negligible.

• The plasma is in a steady state.
• All lines are optically thin.
• Line emissivities are reliable only in some (extended) temperature and density ranges. The ranges of temperatures at which the original rates were calculated are normally listed in the files.
• The current ion fractions that are provided within CHIANTI have been calculated assuming equilibrium and without taking into account density effects.
• DEM files are provided only as samples of DEM curves for different physical conditions in the solar atmosphere: the intensities they generate may differ from observed values.

4.3  How to acknowledge CHIANTI

The continued development of the CHIANTI database is dependent on continued funding which is generally available if we can demonstrate that the CHIANTI database is of use to astrophysical research. If you use CHIANTI, we only ask that you acknowledge it appropriately in any publications:

Write in the text of any publication the reference to the CHIANTI paper associated with the particular VERSION you have used:

• 1.x - (Dere et al., 1997; AASS, 125, 149)
• 2.x - (Landi et al. 1999; AASS, 135, 339)
• 3.x - (Dere et al., 2001; ApJSS, 134, 331 )
• 4.x - (Young et al., 2002 ).
• 5.0 - (Landi et al., 2005 )

We would appreciate if you also write in the acknowledgements of any publication the following:

CHIANTI is a collaborative project involving NRL (USA), RAL (UK), and the following Universities: College London (UK), of Cambridge (UK), George Mason (USA), and of Florence (Italy).

If a detail work on a particular ion is done, it would be appropriate to also refer to the original publication. References can be found at the end of each data file or on the WWW.

CHIANTI data are included into other databases. It would be appropriate to make that clear to the users so they can trace back the results they use to the original calculations.

Users should be aware of what is included in the database, of the approximations applied, and of the atomic data used. The CHIANTI results should not be blindly considered valid in all cases. For example, the CHIANTI predicted emissivities should not be used when considering temperatures outside of the validity ranges.

Any contributions and suggestions to CHIANTI are welcomed. We would appreciate a short description of how you employ CHIANTI.

4.4  The CHIANTI consortium members

The CHIANTI project was originally set up by Dr. Ken Dere of the Naval Research Laboratory (Washington, USA), Dr. Helen Mason of the Department of Applied Mathematics and Theoretical Physics at the University of Cambridge (UK), and Dr. Brunella Monsignori-Fossi of the Arcetri Astrophysical Observatory (Florence, Italy). Former students of Dr. Monsignori-Fossi (Dr. Enrico Landi) and Dr. Mason (Dr. Peter Young) helped in the creation of the database. The sad and unexpected death of Dr. Monsignori-Fossi in January 1995, led to Prof. Massimo Landini, a close associate of Dr. Monsignori-Fossi, becoming a new CHIANTI representative (University of Florence).

Additional collaborations have involved Dr. Dave Pike of the Rutherford Appleton Laboratory (RAL), who has written CHIANTI routines to run within the environment of the SOHO/CDS software (and within SolarSoft), and with Dr. Gordon Bromage, Dr. Barbara Bromage and her former student Dr. Giulio Del Zanna of the University of Central Lancashire.

Dr. Enrico Landi, now at the Naval Research Laboratory, Dr. Peter Young, now at RAL, and Dr. Giulio Del Zanna, now at UCL, have continued to be active collaborators in the CHIANTI project.

4.5  A short history of the package

1. The first version of the CHIANTI database was released in 1996 and is described in Dere et al. (1997).

   Young et al. (1998) used the CHIANTI database for a detailed comparison with observed EUV solar spectra to assess the diagnostic accuracy of the two data sets.

2. Version 2.0 (Landi et al. 1999) was released in April 1999. This Version adds atomic data for many of the so called minor ions (Na, P, Cl, K, Ti, Cr, Mn, Co, and Zn), not included in the first version. Because the astrophysical abundances of these elements are relatively low, only the strongest lines of these elements are observed. The addition of the minor ions is an important step in our goal to understand astrophsical spectra in detail. In addition, Version 2.0 extends the beryllium-like sequence, updates some of the data in Version 1, and provides an IDL procedure to calculate the continuum.
3. Version 3.0 of the CHIANTI database was released in September 2000 (Dere et al., 2001). In this version the database has been extended to wavelengths shorter than 50Å by including atomic data for the hydrogen and helium isoelectronic sequences, inner-shell transitions and satellite lines and several other ions. In addition, some of the ions already present in the database have been updated and extended with new atomic data from published calculations. The inclusion of the satellites has required a significant modification to the manner in which the spectra have been calculated with CHIANTI. Consequently, a new version of the IDL software has been produced.

   In November 2000 we have released a whole new CHIANTI package under SolarSoft.

4. Version 4 of the CHIANTI database, released in Sept. 2002 (Young et al., 2002). The major changes are the inclusion of proton excitation data, principally for ground configuration levels which are close in energy, and of photoexcitation.

   The fitting procedure for excitation data, both electrons and protons, has been extended to allow 9 point spline fits in addition to the previous 5 point spline fits. This allows higher quality fits to data from close-coupling calculations where resonances can lead to significant structure in the thermally-averaged collision strengths.

   With the addition of H I, He I and N I, the first neutral species have been added to CHIANTI.

   Many existing ion data-sets have been updated, in particular most ions of the nitrogen and beryllium isoelectronic sequences. Also, new ions have been added, including Ar IV, Fe VI and Ni XXI.

   The continuum routines have been re-written, including a new relativistic free-free continuum, a new free-bound, and a new two-photon continuum. New software has been written.

Minor releases of the database and the software normally include fixes and might occur a few times per year.

4.6  How to keep updated on CHIANTI developments

• Read the CHIANTI NEWS page on the WWW.
• Read the HISTORY (software) and README (database) files in the distribution. Any news and changes are logged in these files. The first one has the details of all the software changes, while the second one describes the changes to the database. These files can be found directly in the distribution or via links on the WWW pages.
• We maintain an e-mail list, that is used to distribute information about any developments of the CHIANTI database and programs. To get on the CHIANTI e-mailing list, send us an email.
• We also have an e-mail adress for questions:

  chianti_help@halcyon.nrl.navy.mil    
  
  

5  The database structure

The atomic data will continue to be updated regularly as new data are calculated or measured in the laboratory.

It is intended that these atomic data can be accessed and transfered into users own analysis programs, for more sophisticated applications.

5.1  Directory structure and atomic data file contents

The database has a tree structure, with the top directory designated with the IDL system variable !xuvtop (and named dbase within SolarSoft):

dbase/

In the top directory are the following files:

        README_CHIANTI   with the description of the current version.
        VERSION	         with the version number.

Then, there is a series of subdirectories, one for each element present in the database. 
Each element has  a subdirectory  for each ion. 
The filename prefix for each ion follows spectroscopic notation.
For example, for He, we have He I and He II subdirectories:

        he/
           he_1/
           he_2/

Then, we have a series of ancillary data that are contained in 
various subdirectories:

        masterlist/
                         has the list of the ions currently present
                         in the database
        abundance/       with elemental abundance files.
        continuum/       contains files for the continuum calculations.
        dem/             has DEM files.
        ioneq/           contains ionization fraction files.
        ip/              has ionization potentials.
        ancillary_data/instrument_responses/      with effective areas.

There are five primary ASCII files for each ion subdirectory. For example, for Fe XIV we have:

• fe_14.elvlc

  Specifies the energy levels in cm^-1 and Rydbergs. It includes both experimental data and theoretical values of the levels energies.

  The energy levels are obtained from NIST. Where necessary, these are supplemented by other laboratory and theoretical values.

  Each column in the files has:

  1. Index of the fine structure energy levels. This index applies to all files for this ion.
  2. Configuration number, a progressive number. This value is not used by the software.
  3. Designation of the fine structure level,usually using the notation of LS coupling.
  4. Integer value of 2S+1, S=spin in standard usage
  5. Integer value of angular momentum L.
  6. Symbol for L, i.e. S for L=0, P for L=1, D for L=2, etc.
  7. Total angular momentum J
  8. Multiplicity or statistical weight: 2J+1 This value is not used by the software.
  9. observed energy in cm^-1 (if there is no observed value, it is set to zero). This value is used by the software.
  10. Observed energy in rydbergs This value is not used by the software.
  11. theoretical energy in cm^-1 (usually this is the energy from the scattering calculation, but not necessarily). This value is used by the software.
  12. Theoretical energy in rdybergs. This value is not used by the software.
  13. There might be further columns but these are not read by the software.

  Note that the ordering of the levels does not follow any strict rule.

• fe_14.wgfa

  Contains the wavelengths, gf and A values of the transitions and the indices initial and final level corresponding to the indices of the levels as given in the fe_14.elvlc file. Wavelengths calculated from the theoretical energies are of an indeterminate accuracy and their values are presented as negative values of the calculated wavelength. The `observed' wavelengths in these files are based on the experimental energies and should be the best available.

  The radiative data are taken from published literature and where necessary, supplemented by new calculations.

  Each column in the files has:

  1. index of the lower energy level (consistent with the ordering in the .elvlc file)
  2. index of the upper energy level
  3. wavelength in Angstroms. If the wavelength does not connect 2 observed energy levels, the wavelength is given as a negative number. Two-photon transitions are given a zero wavelength.
  4. gf value (weighted oscillator strength)
  5. A-value
  6. In some cases additional columns have extra information on the transition. These are not read by the software.
• fe_14.splups

  contains the point spline fits to electron collision strengths scaled according to the the rules formulated by Burgess and Tully (1992), as described in Dere et al. (1997). All the atomic data in the CHIANTI database have been visually displayed and assessed for accuracy and any sporadic errors which sometimes creep into published results.

  Accurate replication of the temperature averaged collision strength over a wide range of temperatures can be accomplished with the data in this file.

  Each column in the files has:

  1. Z (6 = C)
  2. ion (3 = III)
  3. index of the lower level (consistent with the ordering in the .elvlc file)
  4. index of the upper level
  5. transition type: see Burgess and Tully, 1992, A&A. types 1-4 follow Burgess and Tully for a 5 point spline fit type 5 = dielectronic recombination excitation rate types 6-9 are the same as 1-4 but for 9 point spline fits
  6. gf-value
  7. Energy difference between the two levels in Rydbergs
  8. Value of scaling parameter 'C' (cf. Burgess and Tully, 1992, A&A).
  9. 5- or 9-point values (spline fits) of the scaled Upsilons.
• fe_14.psplups

  This is analogous to the fe_14.splups file, and contains the point spline fits to proton collision strengths.

• fe_14.fblvl contains data used for the free-bound calculation. Namely, the statistical weights for each nl shell, and the energy levels in cm^-1.

5.1.1  Ionization/recombination

We created two new files that include the a_ion and a_rec rates. The names of these files follow the usual CHIANTI pattern, and have the .CILVL and .RECLVL suffixes, for ionization and recombination respectively.

Data in these files are tabulated as a function of temperature, at all temperatures for which they are provided.

Currently, all the rates for each ion are given at the same temperature. In the future this will be generalised.

5.1.2  Final comments

The basic structure of the files is to put the data at the beginning of the file followed by comments.

The comments must be enclosed at the end of the file between two lines containing a single '-1'

The original sources are documented in each data file, where also additional and detailed comments written by the CHIANTI member that assessed that particular ion can be found. You can have direct access to the references via the WWW pages.

5.2  Additional ancillary data

Some additional data files are needed in various calculations. The software allows the selection of these files, from either a 'standard' selection provided within the database, or by using user defined files that are included in the current working directory, provided they have the proper file extension. For example, it is possible to create a user defined 'myfile.dem'. If the file is in the working directory, then the file will automatically be appended to the list of available DEMs from the CHIANTI database. In other cases, it is possible to select the file by using a widget that allows the user to change directory.

Any user-defined file must have the same format as those already provided (also including a 'comment' section at the end of the file)

The list of the ions present in the database

A !xuvtop/masterlist/masterlist.ions file keeps the current list of all the ions in the database. This list is used as default by many routines (for example those that calculate line intensities).

In some cases, it is possible to instead use a user-defined list of ions, to speed the calculation, or to directly supply the routines with a list of ions, via the SNGL_ION keyword.

Elemental abundances

Files with various elemental abundances are provided in the directory !xuvtop/abund/ Element abundances are in the usual dex notation (Log₁₀ values, relative to H, that has a Log₁₀ value of 12).

Options are available within the routines to choose different elemental abundances. User-defined abundance files can also be used, and should have a .abund file extension.

Be aware that any element missing in the elemental abundance file will also be missing in any output created by any software that reads the elemental abundance file.

There is a great deal of controversy over the variation of the elemental abundances in the solar and stellar atmospheres. See the reviews of Meyer (1985, 1993), Widing and Feldman (1992), Mason (1992), Raymond et al. (2001). Also, it should be kept in mind that different analyses can lead to very different results. For example, the ionisation balance, the selection of lines, and the spectroscopic method used can each account for a variation of a factor of two or more in the derived element abundances (see Del Zanna et al., 2002 and references therein).

Ionisation Fractions

Files giving collisional ionization equilibria are provided in the !xuvtop/ioneq directory. User defined ionisation files should have a .ioneq file extension.

Be aware that most CHIANTI software uses the temperatures in these files as a base for the calculations. For example, if DEM(T) values are supplied, they are first interpolated at the temperatures in the ionization fraction, and the calculations are done at those temperatures.

The ionisation fractions have been taken from the tabulated values in the published literature (e.g. Arnaud & Raymond, 1992; Arnaud & Rothenflug, 1985; Mazzotta et al., 1998).

Be aware that any ion missing in a ionisation fraction file will also be missing in any output created by the software.

Also, be aware that any line missing a temperature overlap with the chosen ionisation fraction would have zero emissivity and will not be output by the software.

Be aware that large differences between different tabulations are present, and that large uncertainties are associated with these calculations. It should be noted that the ionisation equilibrium plays a major role not only in the derivation of the DEM, but also in that one of the elemental abundances. In this respect, it is important to be aware of the fact that a number of ions, in particular those of the Li and Na isoelectronic sequence, present anomalous behaviour (see Del Zanna et al., 2002, and references therein).

Differential Emission Measure

Files specifying various standard differential emission measures (DEM) distributions for different solar features are provided in the !xuvtop/dem directory. Additional files for stellar atmospheres will also soon be added. Each file contains the Log₁₀ T and Log₁₀ DEM values in two columns, ordered with increasing temperature.

User-defined DEM files should have a .dem file extension and must have the same format and ordering of the files provided.

Be aware that any line missing a temperature overlap between the ion fraction and the chosen DEM distribution would have zero emissivity and will not be output by the software.

The emission measure distribution in the solar atmosphere is a complex issue. Starting with the pioneering work by Pottasch (1964), spectra in the UV wavelength range have been used to determine the distribution of material as a function of temperature, following various methods. More details can be found in Section 9.16.

Other files

Other files are in other miscellaneous directories. For example:

!xuvtop+'/ip/chianti.ip' has the ionization potentials for all the ions;

!xuvtop+'/continuum/ contains data used by the routines that calculate the continuum. For example, gffgu.dat contains the free-free gaunt factors of Sutherland (1998).

6  The Software structure

A number of Interactive Data Language (IDL) procedures are also provided as part of the CHIANTI package. These include routines to read the various CHIANTI database files, calculate level populations, line intensities, and temperature dependent and density dependent line intensity ratios.

Most of our efforts have gone into developing well-documented user-friendly IDL routines that meet readily apparent needs. We welcome contributions to the software.

CHIANTI has been run mainly on Sun, Dec Unix workstations and on PCs with Linux. CHIANTI also runs (with some small limitations) under Windows NT and in VMS. Please report to us any problems you might find.

All the IDL routines have been documented with extensive headers giving detailed descriptions and examples. Please read them carefully.

The CHIANTI routines can be grouped into three classes:

• Low-level routines, that for example read the files in the database, or perform the level population calculations. These are not described here and should not be used directly byt the users.
• High-level routines, that perform more complex operations and can be called from the command line. These routines usually output arrays or structures, and optionally produce plots, postscript output or ascii files. Most of them have a long list of options, commanded via KEYWORDS. Please read the headers.
• Higher-level widget-type routines. These routines are more user-friendly, and are complementary of the above class. These routines call low-level or high-level routines to perform the calculations.

The CHIANTI routines are organised in a tree structure. The main level contains some high-level procedures and the HISTORY file, where all modifications to the software are logged.

6.1  Short description of the CHIANTI software

Now, a description of the various high-level routines that are present within the CHIANTI software tree is given.

Compared to previous releases, significant changes occurred. Please read Sect.  for details.

A new set of high-level and higher-level routines has been written for Version 4. The major change for V.4, aside from those already mentioned, has been the way to calculate synthetic spectra and handle line intensities (see Fig. 1):

• A new routine, ch_synthetic.pro, calculates (without any abundance factor) line intensities or G(T), and outputs a line intensities CHIANTI structure (see Sect.E.1 for details). This IDL structure can be saved and later restored in various ways, for example using ch_write_fits and ch_read_fits.
• ch_line_list.pro takes the line intensities CHIANTI structure and creates ascii or latex files with lists of line identifications and intensities.
• make_chianti_spec.pro This program creates the CHIANTI SPECTRUM structure (read Sect. E.2 for details), that contains the synthetic spectrum, created by multiplying by the abundance factor the line intensities and adding the continuum (optional).
• Finally, a new multi-purpose widget ch_ss.pro has been written. It includes all the above features.

Other routines that previously were only available within SolarSoft are also included now. The users therefore now have various different routines to choose from.

We have kept the older high-level routines, so the user can still use them as before (with slight modifications/additions of keywords). We have updated them and re-written as wrapper routines (essentially that call the newly-written routines) as follows:

6.2  How to find help

For the first two classes of routines, by simply typing the name of the routine, a description of how to call the routines, with examples, is printed. For example,

 IDL > temperature_ratios
 IDL > temperature_ratios,ion,wmin,wmax,Log10(tempmin),Log10(tempmax),$
 IDL > temperature,ratio,description,$
 IDL >  [pressure= ,density= , psfile= , outfile= ]
 IDL > 
 IDL > i.e.:
 IDL > temperature_ratios,'c_5',40.,50.,5.,7.,temp,rat,desc

In any case the best way to understand what a routine does and how it works is to read the header documentation with e.g.:

 IDL > xdoc,'ch_synthetic'
 IDL > doc_library,'ch_synthetic'

Another way to quickly see the keywords of a routine is to use:

 IDL > chkarg,'temperature_ratios
 .....
---> Call: pro temperature_ratios,ions,wmin,wmax,tempmin,tempmax,$
temperature,ratio,description,$
density=density,psfile=psfile, $
outfile=outfile,noprot=noprot, $
radtemp=radtemp,rphot=rphot,photons=photons, $
ioneq_file=ioneq_file, abund_file=abund_file, $
VERBOSE=VERBOSE

7  The CHIANTI distribution and installation

CHIANTI is currently distributed in two ways:

1. as an independent package within SolarSoft, a programming and data analysis environment for the solar physics community. See

   http://www.lmsal.com/solarsoft/

   for details on how to download and install the package. The database and the software are organised in a self-contained package

   $SSW/packages/chianti/ 
   
   

   with the following tree structure:

   dbase/    (database)
   doc/      (documentation, in particular the USER GUIDE)
   idl/      (IDL software)
   setup/    (supplementary setup files)
   
   

   The contents of the SolarSoft CHIANTI package are mirrored daily from a master tree. Normally, only small fixes to the existing software can occur rather frequently.
   

   All modifications to the software are logged in the $SSW/packages/chianti/idl/HISTORY file.

   Modifications to the database are much less frequent. They are described in the $SSW/packages/chianti/dbase/README_CHIANTI file.

   We send an e-mail to the CHIANTI user group every time we make a minor release of the database available.

   Note that the contents of the SolarSoft package change on a frequent timescale normally to fix bugs caused by the use of new IDL releases.

   We recommend that you use CHIANTI within the SolarSoft framework and that you setup in your site a mirror in order to have automatic upgrades. It is easy to follow the instructions to download and setup the package.

2. On the WWW, as tar files, via one the WWW CHIANTI pages, e.g.:

   • RAL, UK: http://www.chianti.rl.ac.uk/
   • NRL, USA: http://wwwsolar.nrl.navy.mil/chianti.html

   Currently, the data and the software are distributed in two separate tar files. The tar files have a similar tree structure as the SolarSoft distribution.

   E.g. the data are in CHIANTI_4.0_data.tar that contains a copy of $SSW/packages/chianti/dbase.

   CHIANTI_4.0_pro.tar contains doc/, a copy of $SSW/packages/chianti/doc/ and idl/, a copy of $SSW/packages/chianti/idl/, plus idl/gen/, a copy of the $SSW/gen/ routines. This is because some routines of the $SSW/gen/ directory are needed to run some of the CHIANTI programs.

   CHIANTI is a package, in the sense that database and progams are to be used together. The current version of the database must be used with the current version of the programs. Backward compatibility does not always apply.

7.1  Installing CHIANTI

To run any CHIANTI IDL procedure, the following is needed:

• Access to the CHIANTI IDL routines. The IDL !PATH should contain the paths to the directories where the CHIANTI IDL procedures are.
• Access to the CHIANTI atomic database and ancillary data. This is done by defining the system variable !xuvtop, that should point to the CHIANTI atomic database top directory.
• The following IDL system variables need to be defined:

  • !xuvtop the top directory for the atomic database
  • !ioneq_file the default ionization equilibrium file
  • !abund_file the default elemental abundance file
  • !BCOLOR , !ASPECT

7.1.1  Installing CHIANTI within SolarSoft

If you are using SolarSoft you should have the setup already organised so as to have the path of the CHIANTI IDL procedures added to IDL_PATH, the !xuvtop and the other IDL system variables defined. This is done automatically by using

 unix> setssw chianti 
 unix> sswidl 
or
 unix> sswidl 
 IDL > ssw_packages,/chianti  

After this, you will be able to run the CHIANTI routines.

7.1.2  Installing CHIANTI independently as a stand-alone

Users of previous versions, please NOTICE:

The procedures to install CHIANTI have changed in small but important ways.

Download the CHIANTI files

Download the CHIANTI data tar file (e.g. CHIANTI_4.0_data.tar.gz) and the CHIANTI IDL procedures tar file (e.g. CHIANTI_4.0_pro.tar.gz) and put the tar files into a directory (for example, /data1/chianti/dbase for the data and /data1/chianti/ for the software) and then do the following:

unix> gunzip [file_name].tar.gz
unix> tar xvf [file_name].tar

This will copy all the CHIANTI data files into /data1/chianti/dbase and create the /data1/chianti/idl and /data1/chianti/doc/ directories.

Define the IDL paths and the system variables

There are two ways of doing the above. The first is to define the system variables within IDL, the second is outside IDL. We suggest the first option. Once IDL is started, there are three steps:

unix > idl
 

1. add to the IDL PATH the path of where the CHIANTI IDL routines are:

   Unix: IDL> !PATH = '+/data1/chianti/idl:'+!PATH
   Windows: IDL> !PATH = '+C:\data1\chianti\idl;'+!PATH
   VMS: IDL> !PATH = '+/data1/chianti/idl,'+!PATH
   
   

2. IDL> !PATH = EXPAND_PATH(!PATH)
    
   

   The '+' and the EXPAND_PATH are needed since the IDL routines are organised into subdirectories. The second option involves writing (UNIX) the following statement in your  /.cshrc (or  /.login) file:

   setenv IDL_PATH /usr/local/rsi/idl_4/lib:+/data1/chianti/idl
   
   

   (assuming you have the main IDL directory in /usr/local/rsi/idl_4).

3. Unix:  IDL> use_chianti, '/data1/chianti/dbase'
   Windows: IDL> use_chianti, 'C:\data1\chianti\dbase'
   
   

After following the above steps, it will be possible to run the CHIANTI routines from any directory. use_chianti also allows you to set your default abundance and ionization equilibria files with the abund and ioneq keywords.

Previous CHIANTI users should check the note below.

We suggest that you add the three above calls to your IDL_STARTUP file (say  /.idl_startup). If this file does not exist then it should be created. In UNIX, this can be done if you add the following line to your .login file:

setenv IDL_STARTUP ~/.idl_startup

(Note that the changes to the .login file mean that you should do a source ~/.login before running IDL).

Alternatively, you can write the three statements above in a file, say start_chianti.pro:

 !PATH = '+/data1/chianti/idl:'+!PATH
 !PATH = EXPAND_PATH(!PATH)
 use_chianti, '/data1/chianti/dbase'
 END
 

 IDL> .r start_chianti
 

Note to previous CHIANTI users:

If you had already defined the CHIANTI system variables before entering IDL or in your IDL STARTUP file you should remove those definitions.

Alternatively, instead of using use_chianti, '/data1/chianti/dbase', you have to make sure you have in your IDL STARTUP file something like this:

 !PATH = '+/data1/chianti/idl:'+!PATH
 !PATH = EXPAND_PATH(!PATH)
defsysv,'!xuvtop', '/data1/chianti/dbase'
defsysv,'!ioneq_file','/data1/chianti/dbase/ioneq/mazzotta_etal.ioneq'
defsysv,'!abund_file','/data1/chianti/dbase/abundance/cosmic.abund'
defsysv,'!BCOLOR',0
defsysv,'!ASPECT',1.0

8  Theory and definitions

8.1  Optically thin emission lines

For a review on Spectroscopic Diagnostics in the EUV for Solar and Stellar Plasmas see e.g. Mason and Monsignori Fossi (1994).

The intensity I(l_ij), of an optically thin spectral line of wavelength l_ij (frequency n_ij = [ c/(h l_ij)]) is

I(lij)=  h nij 4 p    ó õ Nj   Aji  dh    [ergs  cm-2  s-1  sr-1]

(1)

where i, j are the lower and upper levels, A_ji is the spontaneous transition probability, N_j is the number density of the upper level j of the emitting ion and h is the line of sight through the emitting plasma. In low density plasmas the collisional excitation processes are generally faster than ionization and recombination timescales, therefore the collisional excitation is dominant over ionization and recombination in populating the excited states. This allows the low-lying level populations to be treated separately from the ionization and recombination processes.

For allowed transitions we have N_j(X^+m) A_ji ~ N_e. The population of the level j can be expressed as:

Nj(X+m) =  Nj(X+m) N(X+m)     N(X+m) N(X)     N(X) N(H)  N(H) Ne   Ne

(2)

• N(X^+m)/N(X) is the ionization ratio of the ion X^+m relative to the total number density of element X (contained in the files in the ioneq/ directory);
• Ab(X)=N(X)/N(H) is the elemental abundance relative to Hydrogen (contained in the files in the abundance/ directory);
• N(H)/N_e is the Hydrogen density relative to the free electron density. Often assumed to be equal to 0.83, as hydrogen and helium are usually completely ionised for hot optically thin plasmas.

  See the routine PROTON_DENS described in Sect. B.5 for details on how to calculate N(H)/N_e.

• The fraction n_i = [(N_j(X^+m))/(N(X^+m))] of ions X^+m lying in the state j is determined within CHIANTI by solving the statistical equilibrium equations for a number of low-lying levels of the ion including all the important collisional and radiative excitation and de-excitation mechanisms.

In the `standard model' for interpreting line intensities there are three fundamental assumptions that serve to simplify the problem considerably:

1. the plasma is in a steady state;
2. atomic processes affecting the ionisation state of an element can be separated from those affecting the level balance within an ion;
3. all lines are optically thin.

The atomic data contained in the CHIANTI database are particularly suited to the analysis of emission lines via this model, and the following discussion outlines this approach. No attempt is made to discuss non-equilibrium conditions.

With the first of the assumptions, the population of ions lying in a given state is constant and so the number of ions leaving this state per unit time must exactly balance the number arriving into that state. If we denote the number of transitions leaving the state i to a state j taking place per unit time per unit volume by a_ij, then steady state implies

Ni å j ¹ i  aij = å j ¹ i  Nj aji.

(3)

Setting

aii = - å j ¹ i  aij

(4)

we have

å j  Nj aji = 0

(5)

for each state i and, as the coefficients a_ji are independent of the state populations, we have a set of linear equations to solve for the N_i.

Now our second assumption means that the processes that affect the ionisation state of the plasma do not affect the quantity n_i. Eq. 5 thus becomes

å j  nj aji = 0

(6)

where the a_ji only include those processes that affect the level balance of the ion.

For the basic CHIANTI model these processes are simply electron and proton excitation and de-excitation, and the generalised radiative decay:

aij = Ne Cije + Np Cijp + Aij

(7)

where C_ij^e is the electron excitation-de-excitation rate, C_ij^p is the proton excitation-de-excitation rate, N_p is the proton density, A_ij is the generalized radiative decay rate, that includes A_ij, the radiative decay rate which is zero for i < j (the `A-values' are contained in the CHIANTI .wgfa files), and the photoexcitation and stimulated emission.

C_ij^e is given by:

Cije = Ne qij     i < j

(8)

Cije = Ne  wj wi exp æ è  DE kT ö ø qji     i > j

(9)

where w_i is the statistical weight of level i, k is Boltzmann's constant, T the electron temperature, and q_ij the electron excitation rate coefficient which is given by:

qij=2.172×10-8 æ è  I¥ kT ö ø 1/2   exp æ è -   DE kT ö ø  Uij wi        [cm3 s-1]

(10)

where I_¥ is the Rydberg energy (13.61 eV), and U_ij is the thermally-averaged collision strength for the i ® j excitation. The U_ij are derived from the scaled data in the CHIANTI .splups files.

The solution of Eq. 6 is performed by the CHIANTI routine pop_solver.pro, which gives the fraction of ions in the state i.

The level populations for a given ion can be calculated and displayed with plot_populations.pro (but also see pop_plot.pro).

We rewrite the intensity as:

I(lij) = ó õ Ab(X) C(T,lij,Ne) Ne NH dh

(11)

where the function

C(T,lij,Ne) =  h nij 4 p     Aji Ne     Nj(X+m) N(X+m)     N(X+m) N(X)   [ergs   cm+3   s-1],

(12)

called the contribution function, contains all of the relevant atomic physics parameters and is strongly peaked in temperature.

gofnt.pro calculates these contribution functions (see also g_of_t.pro for a slightly different way of calculating contribution functions).

Please note that in the literature there are various definitions of contribution functions. Aside from having values in in either photons or ergs, sometime the factor [  1/(4p)] is not included. Sometimes a value of 0.83 for N(H)/N_e is assumed and included. Sometimes the element abundance factor is also included. Any of the above (or any other) variations also affect the definition of a line intensity in terms of the contribution function and the DEM. In the following we will refer to the functions C(T,l_ij,N_e) and G(T,l_ij,Ab(X),N_e) = Ab(X)  C(T,l_ij,N_e) ( i.e. the contribution function that contains the abundance factor ).

If we define, assuming that is a single-value function of the temperature, the differential emission measure DEM (T) function as

DEM (T) =  Ne NH  dh dT   [cm-5 K-1]

(13)

the intensity can be rewritten, assuming that the abundance is constant along the line of sight:

I(lij) = Ab(X) ó õ T   C(T,lij,Ne)  DEM (T)   dT    [ergs   cm-2   s-1  sr-1]

(14)

The DEM gives an indication of the amount of plasma along the line of sight that is emitting the radiation observed and has a temperature between T and T+dT.

The IDL routine chianti_dem.pro described in Sect. 9.16 calculates the Differential Emission Measure DEM(T) using the CHIANTI database, from a given set of observed lines.

Routines such as ch_synthetic.pro (see Sect. 9.1 and Sect. ) calculate line intensities without the abundance factor, that is only included at a later stage.

In the isothermal approximation, all plasma is assumed to be at a single temperature (T_o) and the intensity becomes:

I(lij) = C(To, lij, Ne) Ab(X) EMh

(15)

where we have defined the column emission measure

EMh = ó õ Ne NH dh     [cm-5]

(16)

ch_synthetic.pro in the isothermal approximation calculates I = C(T_o, l_ij, N_e) òN_e N_H dh, while isothermal.pro and ch_ss.pro (see examples in Sect. 9.1) can be used to create synthetic spectra (with the abundance factor).

It is also possible to calculate intensities and spectra with a multi-temperature model, by providing an array of T_o, EM_h values.

Please note that in the literature many different definitions of Differential Emission Measures, Emission Measures and approximations can be found (see Del Zanna et al., 2002 for some clarifications).

8.1.1  The stellar case

In the stellar case, the theoretical flux of an optically thin spectral line is:

F(lij) =  1 d2   ó õ V    Ab(X)  C(Ne, T, lij)   Ne NH   dV   [ergs  cm-2  s-1]

(17)

where C(N_e, T, l_ij) has the same expression as above, d is the star's distance, dV is the volume element, and V is the entire source volume. A volume Differential Emission Measures DEM is often defined:

DEM (T) =  Ne NH  dV dT   [cm-3 K-1]

(18)

together with a corresponding volume emission measure EM_V:

EMV = ó õ Ne NH dV     [cm-3]

(19)

At the moment CHIANTI does not include volume emission measures. In the near future we will modify the software and the definition of the DEM in order to include volume emission measures.

However, any volume Differential Emission Measures can be rescaled to column DEMs and used within the software to produce synthetic spectra for stellar coronae. One way of doing this is to assume spherical symmetry, and that the emitting region is a layer dh distributed over the entire star's disk, i.e. dV=4pR²_* dh (R_* is the star's radius). If the star's radius and distance are known, a volume DEM can be scaled with the factor [(4pR²_*)/(d²)] to obtain a column DEM.

If this is used, the outputs will have flux units, i.e. ergs cm^-2 s^-1 (or photons cm^-2 s^-1) and not ergs cm^-2 s^-1 sr^-1.

An example of scaled DEM is provided in the file AU_Mic.dem, in the CHIANTI distribution.

Column DEMs and EMs are assumed when the spectra are folded with effective areas (see Sect. 9.1). The effective areas are assumed to have units of counts photons^-1 cm⁺², so the output units of the spectra will be counts s^-1 pixel^-1.

Also note that corrections to interstellar absorption are not presently included in CHIANTI.

8.2  Proton rates

For each ion for which proton rates are available, an additional file is required in the database to contain the fits to the rate coefficients. The file has the suffix .PSPLUPS, and is exactly analogous to the .SPLUPS file for the electron fits. All of the proton transitions included in CHIANTI are forbidden transitions taking place between levels within the same configuration. Many of the transitions required 9-point splines (see Sect. C) in order to provide adequate fits. The number density of protons, N_p, is calculated with the IDL routine proton_dens.pro (see Sect. B.5).

By default, all routines will include proton rates in the calculation of the ion level balance. A keyword /NOPROT can be used to switch off the proton rates.

8.3  Non-Maxwellian particle distributions

Within CHIANTI the assumption of Maxwellian electron and proton distributions is implicit through the storage of Maxwellian-averaged electron and proton collision strengths in the .SPLUPS and .PSPLUPS data files. To model emission from plasmas with general, non-Maxwellian particle distributions would require integrations of the original collision strengths with the new particle distributions, and this is outside of the scope of the CHIANTI database.

However, if the particle distributions can be expressed as a linear combination of Maxwellians of different temperatures, i.e.,

f(E; ai) = å i  ai fM(E, Ti)

(20)

where the Maxwellian function f_M(E, T_i) is given by

fM(E, Ti)=2 æ è  E p ö ø 1/2   æ è  1 kT ö ø 3/2   exp æ è -  E kT ö ø

(21)

then such distributions can be modelled in a straightforward manner within the CHIANTI framework.

The generalized electron excitation rate coefficient for the transition j to k and for the particle distribution f of electron velocities is given by

Cjk = ó õ ¥ Ejk  Qjk v f(E; ai) dE (22) = å i  ai ó õ ¥ Ejk  Qjk v fM(E,Ti) dE (23) = å i  ai Cjk(Ti) (24)

where E_jk is the threshold energy for the transition, Q_jk is the collision cross section, E (=m_ev²/2, m_e the electron mass) is the energy of the incoming electron, and C_jk(T_i) is the electron excitation rate coefficient for a Maxwellian particle distribution of temperature T_i (see, e.g., Burgess & Tully 1992).

The matrix C_jk replaces the usual Maxwellian-derived rate coefficient (C_jk) in the level balance equations solved by the CHIANTI software. The software routines for calculating emissivities and level populations have been modified to allow input of the non-Maxwellian parameters a_i through the keyword SUM_MWL_COEFFS. The temperatures T_i are specified through the standard temperature input to the routines. The temperatures are assumed to apply to both proton and electron distributions.

This prescription for treating non-Maxwellian distributions is not compatible with the treatment of ionization and recombination since an equilibrium ionization balance described by a single temperature is required for these processes. In such cases the ionization and recombination processes described in Sect.  are switched off when calculating the level populations if the a_i coefficients are specified in CHIANTI.

See Sect. 9.8 for an example.

8.4  Photoexcitation and Stimulated Emission

Within CHIANTI, we presently model the Photoexcitation and Stimulated Emission by assuming a a blackbody radiation field of temperature T_*. The generalized photon rate coefficient in this case is:

Aij = ì ï ï ï í ï ï ï î W(R) Aji  wj wi  1 exp(DE/kT*) -1     i < j Aji é ë 1 + W(R)  1 exp(DE/kT*) -1 ù û     i > j

(25)

where A_ji is the radiative decay rate and W(R) is the radiation dilution factor which accounts for the weakening of the radiation field at distances R from the source center.

We also assume an uniform (no limb brightening/darkening) spherical source with radius R_*:

W =  1 2 é ë 1 - æ è 1 -  1 r2 ö ø 1/2   ù û

(26)

where

r =   R R*

(27)

It is important to remember the assumptions in our formalism for radiation processes. For a given ion, only very specific wavelengths in the radiation continuum will affect the ion's level balance. If there are significant deviations from a blackbody spectrum at any of these wavelengths (perhaps due to a deep absorption line) then CHIANTI does not model the ion entirely correctly.

Examples of specific uses of the extra radiation processes include modeling of coronal emission lines above the surface of the Sun and other cool stars when the coronal electron density falls to low enough values that electron collisions lose their potency.

For the Sun, photoexcitation is very important for the infrared coronal lines. Photoexcitation is also important for modelling nebular ions that are irradiated by a hot star, such as in planetary nebulae, symbiotic stars and Wolf-Rayet stars.

8.4.1  Implementation of Photoexcitation and Stimulated Emission

No additions or modifications to CHIANTI data files are required for photoexcitation and stimulated emission as their rates are entirely determined from the radiative decay rates, level separation energies, and statistical weights - information already contained in CHIANTI. It is only necessary to specify the radiation field temperature and the dilution factor. These are specified as inputs to the IDL procedures through the new keywords RPHOT and RADTEMP. RPHOT specifies r = [  R/(R_*)], while RADTEMP gives the blackbody radiation temperature in K.

By default, photoexcitation and stimulated emission are not included in the level balance equations unless the keywords are set.

8.5  Photoexcitation by arbitrary radiation fields

Version 4 of CHIANTI introduced the possibility of including photoexcitation and stimulated emission through an external blackbody radiation field into the level balance equations. With version 5 the software has been modified to allow an arbitrary, user-defined radiation field to be specified.

The user must create an IDL routine that calculates the energy density per unit wavelength, U_l, as a function of wavelength. The photoexcitation rate for a transition i® j is related to U_l by the expression

Pij=Aji W(R)  wj wi  l5 8phc Ul

(28)

where W(R) is the dilution factor defined as in Young et al. (2003), A_ji is the Einstein coefficient for spontaneous radiation from j to i, w_j and w_i are the statistical weights of levels j and i. or example, U_l for a blackbody of temperature, T, is given by

Ulbb =  8phc l5  1 exp(hc/lkT) -1

(29)

thus giving the photoexcitation rate for a blackbody of

Pbbij=Aji W(R)  wj wi  1 exp(E/kT) -1

(30)

For reference we note that the energy density is related to the specific intensity, I_l, by

Il =  c 4p Ul.

(31)

The user-defined radiation field function is implemented through a keyword
RADFUNC='user_function, a, b' in the CHIANTI IDL routines SHOW_POPS and
EMISS_CALC. The optional coefficients a and b can be used to modify the radiation field, e.g., by specifying a relative velocity between the radiation field and incident ion.

See Sect. 9.7 for an example.

8.6  Ionization and recombination

In Version 5 of CHIANTI, we have included ionization and recombination into level populations. The CHIANTI model for ionization and recombination assumes that the plasma can be described under the Coronal Model Approximation, where the total population of the excited levels of an ion is negligible compared to the population of the ground level. In this case, recombination and ionization processes can be included in a relatively straightforward way, since they can be treated as a correction to the case where populations are calculated neglecting them.

To illustrate this method, we will consider the simplified atomic model of an ion X^+q with abundance n_q composed of the ground level and one excited level only. In case ionization and recombination contributions to level populations are negligible, the relative population of the upper level is obtained by solving the equation:

NgNeCg® i = NiAi® g        Þ        æ è  Ni Ng ö ø ion/rec  =  NeCg® i Ai® g

(32)

where C_{g® i} is the collisional excitation rate and A_{i® g} is the Einstein coefficient for spontaneous radiative decay. Collisional de-excitation is neglected in the coronal model approximation. In case ionization and recombination provide significant contribution, Equation 32 needs to be modified to include the rate coefficients for ionization (a_ion) and recombination (a_rec):

NgNe(nqCg® i + nq-1aion + nq+1arec) = NiAi® gnq

(33)

where n_q-1,n_q,n_q+1 are the ion fractions for the ions X^q-1, X^q and X^q+1, respectively. The population of the excited level can then be expressed as

æ è  Ni Ng ö ø ion/rec  = æ è  Ni Ng ö ø no ion/rec  ×À (34)

where the correction À is given by

À = 1 +  nq-1aion + nq+1arec nqCg® i (35)

The correction À is temperature sensitive and can be large when the collisional excitation rate is small or when the abundance of the ion q is much smaller than the abundances of the adjacent ions. The correction due to ionization and recombination can have significant effects on intensities of observed X-ray lines.

The only limitation of this approach lies in the breakdown of the coronal model approximation at high densities for a few ions. This occurs at densities above which metastable level populations begin to be non-negligible, compared to the ground state (cf. Landi et al. 2005).

The CHIANTI software has been modified to allow calculation of the correction factor À for the ions for which a_ion and a_rec are provided.

The inclusion of ionization and recombination effects in level population has required some more changes. New files have been created (.CILVL and .RECLVL) to store the ionization and recombination rates necessary for this process (see Sect. 5.1.1 for details).

A new routine (READ_IONREC.PRO) has been created to read these files and store their data in the input to the routine POP_SOLVER.PRO. This latter routine has been modified to include the correction to the level populations. In case the .CILVL and .RECLVL files are not available, a flag is set in the programs and these processes are ignored. The impact of this new process on the running time is negligible.

However, the introduction of ionization and recombination effects on level population has had a side effect. In previous versions of CHIANTI, the contribution to the intensity of spectral lines from levels below the ionization potential due to cascades from levels above the ionization potential was taken into account in the ``dielectronic'' .WGFA files, which included radiative transitions from the former, populated by cascades from the latter. For the ions for which the complete .RECLVL and .CILVL files are now available (Fe XVII to Fe XXIV), cascades from levels above ionization are now taken into account directly, so that the cascade contribution calculated by the ``dielectronic'' .WGFA files is not anymore necessary. To avoid double-counting this contribution, the transitions from levels below the ionization threshold in the ``dielectronic'' .WGFA files have been given a null wavelength, so they can be removed from the spectrum without having to change the way the ``dielectronic'' level population are handled.

8.7  Continuum calculations

An IDL routine to include the two photon continuum has been added to CHIANTI, while the free-bound and free-free continuum (bremsstrahlung) routines have been revised. See Young et. al. (2002) for more details.

Note that the output units of the continuum routines are by default 10^-40 ergs sr^-1 s^-1 Å^-1 per unit emission measure òN_e N_H dh.

On the other hand, the SolarSoft routine CONFLX outputs a continuum in photons s^-1 Å^-1 assuming an emission measure òN_e² dh = 10⁵⁰.

8.7.1  Two photon continuum

The two-photon continuum is calculated with two_photon.pro.

Transitions in hydrogen-sequence ions

The first excited level (2s ²S_1/2) of the hydrogen iso-electronic sequence ions can decay only by means of forbidden magnetic dipole and two-photon transitions. The importance of the competing magnetic dipole transition increases with Z but for nickel (Z=28), the two-photon transition rate is roughly 5 times that of the magnetic dipole rate.

The spectral emissivity (erg cm^-3 s^-1 sr^-1 Å^-1) for optically-thin two-photon emission at wavelength l is given by:

dei,j dl =  h c 4pl AjiNj(X+m) f(l0/l)

(36)

where A_j,i (sec^-1) is the Einstein spontaneous emission coefficient (A value); N_j(X^+m) is the number density of the level j of the ion X^+m; f is the spectral distribution function; and l₀ is the wavelength corresponding to the energy difference between the excited and ground level.

Two-photon continuum transitions in helium-sequence ions

For the helium iso-electronic sequence, the second excited level (1s2s ¹S₀) decays through a forbidden magnetic dipole and two-photon transitions.

8.7.2  Bremsstrahlung

The bremsstrahlung emission is calculated with freefree.pro. This routine has been rewritten ex-novo. It now includes the Itoh et al. (2000) and Sutherland (1998) gaunt factors.

Itoh et al. (2000) have provided an analytical fitting formula for the relativistic thermal bremsstrahlung gaunt factors, and this is now added to CHIANTI. The fitting formula is valid for the ranges 6.0 £ log T £ 8.5 and -4.0 £ log (hc/klT) £ 1.0. For temperatures below log T=6.0 we retain the non-relativistic Gaunt factors of Sutherland (1998) for computing the continuum. The condition log (hc/klT) £ 1.0 results in some of the low wavelength points being inaccurately represented by the Itoh et al. fitting formula. For these wavelengths the Gaunt factors of Sutherland (1998) are used to compute the continuum level.

The relativistic free-free continuum is almost identical to the non-relativistic continuum at low temperatures. At T=1×10⁸ K (the maximum temperature permitted by the ion balance calculations contained in CHIANTI) the relativistic continuum is around 1% higher near the peak of the distribution.

8.7.3  Free-bound continuum

The free-bound continuum emission is calculated with freebound.pro. This routine has been rewritten. The new routine uses the the Karzas and Latter (1961) approximation to the photoionization cross-sections and calculates free-bound gaunt factors for levels n=1-6. Additional data files have been created for this purpose. For example, free-bound radiation produced by recombination of an electron onto C IV to produce C III will use the data in the c\_3.fblvl file.

9  Some examples on how to use the software

In what follows we review the main points about the new software. We hope you find it useful and enjoy using it !

9.1  Calculating line intensities.

For an user-friendly, widget-based approach the best option is to use CH_SS:

 IDL >ch_ss

This widget allows the user to calculate synthetic spectra in two basic steps. Basically, you follow the various widgets from top left to lower right to set the desired parameters. First calculate the line intensities. These values can be saved for later use. Next, specify further parameters such as the elemental abundances and instrumental spectral resolution and then calculate and plot the spectrum. These values can also be saved for later use. The HELP buttons in the widget provide short descriptions of the required information. More details are given below.

Alternatively, for e.g. background jobs, the routine CH_SYNTHETIC can be used.
ch_synthetic.pro calculates line intensities assuming constant pressure or density (or a model T,N), without the abundance factor. One of the reasons why element abundances are not included in the line intensities calculation is so that it is easier for the user to see how modifying abundances affects their spectra in e.g. ch_ss.pro. The calling sequence is:

IDL> ch_synthetic, wmin, wmax, output=output, err_msg=err_msg, msg=msg, $
      pressure=pressure, density=density, $
      model_file=model_file, all=all,sngl_ion=sngl_ion, $
      photons=photons,  masterlist=masterlist,  $
      save_file=save_file , verbose=verbose,$
      logt_isothermal=logt_isothermal,  logem_isothermal=logem_isothermal,$
      goft=goft, ioneq_name=ioneq_name, dem_name=dem_name, $
      noprot=noprot, rphot=rphot, radtemp=radtemp, progress=progress

The routine has many KEYWORDS (see Sect.  for a full list) A series of parameters must be set:

• 	Wmin, Wmax:   minimum  maximum of the desired wavelength range in Angstroms
  
  

• The (Te,Ne) model for the calculation:

         Pressure:  pressure in emitting region (Pe,  cm^-3 K). 
                    Only a single value is accepted, and the calculation is
                    performed at constant pressure.
  
         Density:   density in emitting region (Ne, cm^-3). 
                    Only a single value is accepted, and the calculation is
                    performed at constant  density, unless LOGT_ISOTHERMAL is
                    defined. In this case, DENSITY can be an array of values, but
                    has to have the same number of elements as LOGT_ISOTHERMAL.
  
  
         model_file    Full path of the (Te,Ne) file if defined. 
                       This file should have two columns, one with the Te (K)
                       values, and one with the Ne (cm^-3) values. If these
                       values are not sorted in ascending order of Te, the
                       routine does sort them.
  
  

• IONEQ_NAME: The ionization fraction file to be used. The program will prompt the user to select one if not defined.
• OUTPUT: The name of the structure containing the line intensities and details.

The line intensities are calculated either in the isothermal approximation, in which case the following has to be defined:

LOGT_ISOTHERMAL:   Array of logarithmic temperatures.
LOGEM_ISOTHERMAL:  Array of logarithmic emission measures (0 by default).

or by folding the G(T) with a differential emission measure DEM contained in the file specified by DEM_NAME. The program will prompt the user to select one if not defined.

Example:

  IDL> ch_synthetic, 10,20., output=str , pressure=1.e+15,$
      ioneq_name=concat_dir(concat_dir(!xuvtop,'ioneq'),'mazzotta_etal.ioneq'),$
         dem_name=concat_dir(concat_dir(!xuvtop,'dem'),'flare.dem'),$
         /photons, /noprot, /all, sngl_ion=['fe_17','fe_18']

Creates an output structure str that contains the line intensities of only Fe XVII and Fe XVIII in the 10-20 Å range calculated at constant pressure of 10¹⁵, with the ionization balance in mazzotta_etal.ioneq and the DEM values in flare.dem in the standard CHIANTI distribution (if not supplied these files can be selected with a widget). Line intensities are in photons  cm^-2 s^-1 sr^-1 (KEYWORD photons), the proton rates are not included (KEYWORD noprot), and all the lines in the database (KEYWORD all) are included (also the lines with only theoretical energy levels).

You can see the contents of the structure with e.g.

IDL> help, str,/st
IDL> help, str.lines[0],/st

9.2  Saving, restoring and exporting the CHIANTI line intensities structure

The CHIANTI line intensities structure can be saved and later restored from the command line in various ways. We suggest two:

1. as IDL binary files using the SolarSoft routines:

   IDL> savegen, file='ch_int_10_20_fe.genx', struct=str
   IDL> restgen, file='ch_int_10_20_fe.genx', struct=str
   
   

   to save and restore the IDL structure str in the file ch_int_10_20_fe.genx.

   Please note that we discourage the use of e.g.:

   IDL> save, file='output.save', output
   IDL> restore, file='output.save'
   
   

   since IDL save files generated with later versions of IDL are usually not readable with earlier versions.
2. as FITS binary tables, that can be easily exported and read by different platforms. We have written two IDL routines:

   IDL> ch_write_fits, str, 'output.fits'
   IDL> ch_read_fits,'output.fits', str
   
   

   to save and restore the IDL structure str in the FITS file output.fits. Aside from an introductory HEADER, the contents of the IDL structure are converted into two binary tables. Extensive comments are added.

In either case, the structure saved in the .genx and .fits files can be restored via CH_SS to later create a spectrum.

9.3  Create a latex or ascii file with all the line details

For an user-friendly approach the best option is to use CH_SS:

 IDL >ch_ss

Alternatively, if you have already calculated a line intensity structure (as shown above), you can use CH_LINE_LIST. This program creates a latex or an ascii file of predicted spectral line intensities and wavelengths corresponding to selected parameters.

The routine has many KEYWORDS. Please read the header or read Sect.  for details. The calling sequence is:

 IDL> ch_line_list, transitions, outname, latex=latex, ascii=ascii, $
      wmin=wmin,wmax=wmax,$
      SPECTRUM=SPECTRUM, abundfile=abundfile, min_abund=min_abund, $
      minI=minI,photons=photons,kev=kev, $
      all=all,no_sort=no_sort, sngl_ion=sngl_ion

Example:

IDL> restgen, file='ch_int_10_20_fe.genx', struct=tran
IDL> ch_line_list, tran, 'ch_line_list.tex', /latex,$
     abundfile=concat_dir(concat_dir(!xuvtop,'abundance'),'cosmic.abund'),$
     mini=1e13

This creates a latex file ch_line_list.tex where only lines with an intensity greater than 10¹³ (KEYWORD mini) are included, and the allen.abund file in the standard CHIANTI distribution is used (if not supplied it can be selected with a widget).

Then, you have to latex the file three times, and optionally xdvi it:

unix> latex ch_line_list
unix> latex ch_line_list
unix> latex ch_line_list
unix> xdvi ch_line_list

If you do not have it already, you will need the package longtable.sty that is distributed as part of ftp://cam.ctan.org/tex-archive/macros/latex/required/tools.tar.gz

You will obtain a table that looks like:

Alternatively, you can also create a latex file with a list of line identifications and intensities using the wrapper routine LATEX_WVL_DEM:

 IDL > latex_wvl_dem,100.,200., pressure=1.e+15,mini=1. 

To create an ascii file with the line details you can follow a similar approach, i.e.:

IDL> restgen, file='ch_int_10_20_fe.genx', struct=tran
IDL> ch_line_list, tran, 'ch_line_list.ascii', /ascii,$
     abundfile=concat_dir(concat_dir(!xuvtop,'abundance'),'allen.abund'),$
     mini=1e13

Alternatively, you can also use the wrapper routine

 IDL > ascii_wvl_dem,100.,200.,pressure=1.e+15,mini=1. 

9.4  Calculating continuum intensities

For example, to calculate the free-free, free-bound and two-photon continuum at a temperature of 5 × 10⁶ K, for wavelengths at 1 Å intervals between 1 and 50 Å:

freefree,5.e+6,findgen(50)+1.,ff 
freebound,5.e+6,findgen(50)+1.,fb
two_photon,5.e+6,findgen(50)+1.,tp

window,0 
plot,findgen(50)+1.,ff+fb+tp,xtit='Wavelength (A)'
oplot, findgen(50)+1.,ff,line=2
oplot, findgen(50)+1.,fb,line=3
oplot, findgen(50)+1.,tp,line=4

Note that the intensities are in units of 10^-40 ergs cm³ s^-1 sr^-1 Å^-1 per unit emission measure òN_H N_e dh (cm^-5).

If DEM values are passed to the routines (via the keyword DEM_INT), it is assumed that they are given as N_H N_e dh/dT . The units are 10^-40 ergs cm^-2 s^-1 sr^-1 Å^-1 in this case.

9.5  Creating a synthetic spectrum with the continuum

The structure created by CH_SYNTHETIC can be restored via CH_SS to create a spectrum. Alternatively, it can be used as an input to the program MAKE_CHIANTI_SPEC. This program creates the CHIANTI SPECTRUM structure (read Sect. E.2 for details), an OUTPUT structure similar to the structure created by CH_SYNTHETIC, with some additional tags. The calling sequence is:

IDL> make_chianti_spec, TRANSITIONS, LAMBDA, OUTPUT, BIN_SIZE=BIN_SIZE,  $
        INSTR_FWHM=INSTR_FWHM,  BINSIZE=BINSIZE, $ 
        WRANGE=WRANGE, ALL=ALL, continuum=continuum, $
        ABUND_NAME=ABUND_NAME, MIN_ABUND=MIN_ABUND, $
        photons=photons, file_effarea=file_effarea, $
        err_msg=err_msg,  verbose=verbose

The routine has many keywords and options. Please read Sect.  for details.

IDL> restgen, file='ch_int_10_20_fe.genx', struct=tran
IDL> make_chianti_spec, tran, lambda, struct,/CONTINUUM, $
     BIN_SIZE=0.01, instr_fwhm=0.1,  WRANGE=[10.,19.],$
      abund_name=concat_dir(concat_dir(!xuvtop,'abundance'),'cosmic.abund')

Some Caveats:

You may find that the calculation is slow. This is usually due to the continuum calculation. In general, it is advisable not to calculate spectra over large wavelength ranges. In any case you can speed up the continuum calculation by reducing the numbers of elements, using the KEYWORD MIN_ABUND.

To see the contents of the structure:

IDL> help, struct,/st
IDL> help, struct.lines[0],/st

While to show the spectrum and the main contributing lines:

IDL> window,0 & plot,struct.lambda,struct.spectrum
      for i=0,n_elements(struct.lines) -1 do $
     if struct.lines[i].peak gt 7e5 then $
   xyouts, struct.lines[i].wvl,  struct.lines[i].peak, struct.lines[i].snote 

It may be useful to save the SPECTRUM structure, that can be later inspected with the widget CH_SS:

IDL> savegen, file='ch_spectrum_10_20_fe.genx', struct=struct
IDL> ch_write_fits, struct, 'ch_spectrum_10_20_fe.fits'

Alternatively, the wrapper routine SYNTHETIC (see Fig 1) can also be used to calculate CHIANTI line intensities. For example:

 IDL > synthetic, 150., 200., 1., pressure=1.e+15, wvl, spectrum, list_wvl, list_ident

will create a synthetic spectrum with a resolution of 1 Å between 150 and 200 Å for a specified set of abundances and differential emission measure at a constant pressure of 1.e+15 (N_e T cm^-3 K). The output arrays wvl, spectrum contain the wavelengths and the intensities (in erg  cm^-2 s^-1 sr^-1 Å^-1 by default). The output arrays ist_wvl, list_ident contain the list of wavelengths and descriptions of the lines that made up the spectrum.

Windows will pop up so that the user can select the abundance file, the ionization equilibrium and the differential emission measure. A spectrum is created by convolving with a Gaussian profile with a FWHM of 1 Å. If the /CONTINUUM keyword had been set, then the continuum would also have been calculated and added to the spectrum. To plot the spectrum and interactively identify lines:

 IDL > synthetic_plot, wvl, spectrum, list_wvl, list_ident, 2.

by clicking the left mouse button, a list of predicted lines within 2 Å of the selected wavelength will be printed out along with their predicted intensity. Clicking the right mouse button will exit the procedure.

9.5.1  Create a spectrum in the isothermal approximation

For an user-friendly approach the best option is to use CH_SS:

 IDL >ch_ss

Alternatively:

 IDL > isothermal, 150., 200., 1., [1.e6], wvl, spectrum,$
       list_wvl, list_ident, edensity=1.e9,$
      ioneq_name=!xuvtop+'/ioneq/mazzotta_etal.ioneq',$
       abund_name=!xuvtop+'/abundance/cosmic.abund'

 IDL>  synthetic_plot, wvl, spectrum, list_wvl, list_ident, 1.

calculates an isothermal synthetic spectrum with a resolution of 1 Å between 100 and 200 Å for a specified set of abundances and differential emission measure at a constant density N_e = 10⁹ cm^-3. The output arrays wvl, spectrum contain the wavelengths and the intensities (in erg  cm^-2 s^-1 sr^-1 Å^-1 by default). The output arrays ist_wvl, list_ident contain the list of wavelengths and descriptions of the lines that made up the spectrum. synthetic_plot can then be used to view the spectrum.

Note: isothermal now is a wrapper routine that calls ch_synthetic . It has particular features. Please read the header documentation.

9.6  The user-friendly multi-purpose widget ch_ss.pro

CH_SS is an user-friendly multi-purpose (see Fig 1) widget that allows the calculation of line intensities (calling CH_SYNTHETIC) and of a synthetic spectrum (calling MAKE_CHIANTI_SPEC) by merging line intensities and continua. The parameters can be interactively set, and the results visually inspected. Line intensities can be saved and restored in various ways. The results can also be stored in various ways, ranging from output plots to tables of line details (using CH_LINE_LIST) or save files.

CH_SS replaces the CHIANTI_SS procedure. The calling sequence is:

       IDL> ch_ss, font=font

Note that if the widget appears too large you can change the font. The widget is organised into four Sections:

9.6.1  SECTION 1 - The Calculation of the CHIANTI line intensities.

This can be done in two ways:

1-Restore a save file with the CHIANTI line intensities already calculated. This is done with the RESTORE button. .genx and .fits files can be restored.

2-Calculate CHIANTI line intensities with a call to CH_SYNTHETIC.

In this case, A series of parameters must be set:

• - Minimum and maximum wavelengths in Angstroms
• - The model used for the calculation. Three are the options: 1) a constant density (cm^-3) 2) a constant pressure (cm^-3 K) 3) a general (Te,Ne) model. In this case, a file will be read. This file should have two columns, one with the Te (K) values, and one with the Ne (cm^-3) values.
• - The ionization fraction file to be used. "*.ioneq" files can be selected from either the CHIANTI database, the working directory or selected via a widget.
• - All ions ? If set to yes (default), then all the ions present in the database will be included.

  If set to no, then it is possible to select a list of ions with a widget

• - All lines ? If set to no (default), only the lines for which there are observed energy levels are included

  If set to yes, also the lines that do not have corresponding observed energy levels are included. In this case, the wavelengths are calculated from the theoretical energy levels, and might not be very accurate.

• - Isothermal ? If set to no (default), a DEM file must be selected. "*.dem" files (i.e. files with a .dem extension) can be selected from either the CHIANTI database, the working directory or selected via a widget.

  If set to yes, then the user is requested to enter one or more temperatures (as logarithmic values - Log T ) and correspondent column emission measures EM logarithmic values. NOTE: if more than one value is entered, then the sequence must be separated by commas (e.g.: 6.0, 6.5, 7.), and both Log T and Log EM must have the same number of values

• - Photoexcitation ? If set to yes, you have to define: Trad: The blackbody radiation field temperature R/Ro: Distance from the centre of the star in stellar radius units
• - Units: Photons or Ergs
• - Protons: If set to Yes, the proton data are used to calculate the level population

Once all the parameters have been defined, the user should click on the "Calculate intensities" button to start the calculation (which calls CH_SYNTHETIC).

Once the calculation is finished, an IDL structure is loaded into memory. It is then possible to save it for later use by clicking on the "SAVE" button.

Once the IDL structure with the line intensities is in the memory, it is then possible to calculate and plot a spectrum (SECTION 2).

9.6.2  SECTION 2 - calculation of a synthetic spectrum

This section controls the parameters that are needed to fold the line intensities and the continua into a synthetic spectrum. These parameters are used by MAKE_CHIANTI_SPEC.

Before this is done, a set of line intensities MUST be in the program memory. This is done either by calculating the intensities or by restoring a save file with previously calculated values (SECTION 1). Setting the parameters:

• -Minimum and maximum wavelengths.
• -spectrum bin size in Angstroms in Angstroms. Disallowed if an Effective area file is used.
• -instrumental FWHM: Setting this to a non-zero value broadens each of the spectral lines with a Gaussian of the specified FWHM (in Angstroms) so mimicking the effects of instrumental broadening.
• -continuum: Add continua to the binned spectrum: free-free, free-bound and two-photon. Please note that the continuum calculation takes some time and you may want to define a minimum abundance value to speed the calculations.
• - All lines ? If set to no (default), only the lines for which there are observed energy levels are included. If set to yes, the ünobserved lines" will be added, but only if they are present in the structure.
• -elemental abundances: "*.abund" files (i.e. files with a .abund extension) can be selected either from the CHIANTI database, the working directory, or via a widget.
• -select a minimum abundance value: If set not null, only the lines of those elements which have an abundance greater than the value set are selected. Also, the continuum is calculated only for those elements which have an abundance greater than the value set. This can significantly speed up the calculations. By default, the minimum value in the selected abundance file is used.
• Eff. Area: (Yes/No): If you want to fold the spectrum with an effective area. If set to Yes, you are requested to choose an input ascii file with two columns, the wavelength and the effective area values (cm²). The spectrum is multiplied with these values. the wavelenghts in the file (that might not be linear) are used to create the spectrum. Note that this option only works well if a sufficient number of bins is given. The line intensities contributing to each bin are summed, and subsequently convolved with a gaussian of full-width-half-maximum FWHM, if FWHM is not set = 0. Please note that the convolution might not work if a small number of bins is defined.

  Also note that to have the correct output units (counts s-1 bin-1) the appropriately scaled DEM (or EM) values must be provided.

After this, by clicking on the "Calculate and plot" button the program calculates and plots the synthetic spectrum.

Once the spectrum is displayed, it is then possible to view the details of the lines by clicking with the mouse in the plot window, and to perform various operations by clicking on the buttons in SECTION 3

9.6.3  SECTION 3 - selection of parameters for plotting and output

This Section allows the user to select a few parameters for the plotting, and to create different types of OUTPUT.

• Labels ? : Setting this to yes plots a vertical line for each spectral line in the spectrum, and also writes a label above the strongest lines indicating the ion from which the line arises.
• Min.: Only lines which have an intensity greater than the value set here will be listed and, if requested, labelled and selected for inclusion in the various outputs. Setting the value=0. will result in all lines being listed and written in the outputs.
• X,Y, XOOM, UNZOOM: It si possible to select a region of the spectrum, by zooming with the use of the mouse or by setting the X,Y ranges.

  NOTE that only the line details and portion of the spectrum shown will be output.

• LINEAR/LOG To plot the spectrum in linear or log scale
• Create PS file: A postscript file is created.
• Hardcopy: the postscript file ïdl.ps" is created and sent to the default printer.
• Save Line details (latex): The details of the lines shown in the plot will be saved in a latex file.
• Save Line details (ascii): The details of the lines shown in the plot will be saved in an ascii file.
• Save Spectrum (ascii): The X,Y values of the spectrum are saved in an ascii file.
• Save Spectrum (IDL/FITS): The details of all the lines and the arrays of the X,Y values of the spectrum are saved into an IDL or FITS file.

Finally, SECTION 4 is a text information window, where various messages are printed.

Clicking the cursor on any part of the displayed spectrum will give a listing of the lines within a range of Angtroms of that wavelength. Text information on the lines is printed.

9.7  Photoexcitation from any user-provided radiation field

The radiation function used in Sect. 2.2 of the v.5 CHIANTI paper for studying the O VI Doppler dimming problem is defined below.

FUNCTION o6_lines, lambda, a

;   Vernazza & Reeves (1978) give the quiet Sun O VI 1032 flux to be
;   305.28 erg/cm2/sr/s. The 1038 line is blended with C II, so I take
;   it to be half of the 1032 line. I assume the FWHMs of the lines are
;   0.2 angstroms.
;
;   A   Velocity (km/s) relative to emitting ions of the structure emitting
;       the radiation field. A positive velocity implies a redshift.

IF n_elements(a) EQ 0 THEN a=0.

siz=size(lambda)
spectrum=dblarr(siz[1],siz[2])

cc=2.998d5   ; speed of light, km/s

p1=305.28/0.2
p2=p1/2.

c1=1031.914
c1=c1+ (a/cc * c1)
;
c2=1037.615
c2=c2+ (a/cc * c2)
w=0.2/2.35

i=where(abs(lambda-c1) LE 6.*w)
IF i[0] NE -1 THEN spectrum[i]=p1*exp(-(lambda[i]-c1)^2/2./w^2)*4.*!pi/2.998d10

i=where(abs(lambda-c2) LE 6.*w)
IF i[0] NE -1 THEN spectrum[i]=spectrum[i]+p2*exp(-(lambda[i]-c2)^2/2./w^2)*4.*!
pi/2.998d10

return,spectrum
END

This function can then be used in show_pops or emiss_calc as follows:

IDL> show_pops,8,6,radfunc='o6_lines, 20',rphot=1.1

where 'o6_lines, 20' indicates that the velocity A is set to 20 km/s. A zero velocity can be set simply by using radfunc='o6_lines'. RPHOT specifies the distance from the centre of the star in stellar radius units.

The effects of many different velocities can be studied by doing, e.g.,

v=findgen(11)*10.
for i=0,10 do begin
  radfunc_string='o6_lines, '+trim(v[i])
  show_pops,8,6,radfunc=radfunc_string,rphot=1.1
endfor

Up to 2 input parameters are allowed for radfunc and are specified by, e.g., radfunc='radfunc, a, b'.

Currently the RADFUNC= keyword is only available for the routines show_pops and emiss_calc.

Another example of radfunc is a blackbody

function udens_bb, lambda

t=6d3    ; temperature of Sun, 6000 K
ee=1.439d8/lambda/t

result=8.*!pi*1.986d-8/lambda^2*(1d8^3)/lambda^3/((exp(ee)-1))
return,result

END

which is specified to show_pops as

IDL> show_pops,8,6,radfunc='udens_bb',rphot=1.1

The user should verify that this gives the same results as using the standard CHIANTI inputs

IDL> show_pops,8,6,radtemp=6000.,rphot=1.1

9.8  Non-maxwellian distribution of electron velocities

The following commands reproduce the numbers in Table 3 of the v.5 CHIANTI paper (Landi et al. 2005). Basically, we want to study the effects of non-Maxwellian distributions on two key line ratios of O VI, involving the strong lines at 1032 Å, 173 Å and 150 Å. We consider a distribution comprised of two Maxwellians at log T=5.5 and log T=6.0, with the coefficients [a1,a2]=[0.75,0.25].

IDL> em=emiss_calc(8,6,temp=[5.5,6.0],sum_mwl_coeff=[0.75,0.25],dens=9.0)
IDL> em150=em[40].em
IDL> em173=em[43].em
IDL> em1032=em[77].em
IDL> print,em150/em1032,em173/em1032
     0.030072876
     0.043500302

The effects of non-Maxwellians on level populations can be demonstrated with the show_pops routine, e.g.,

IDL> show_pops,8,6,lev=-8

Log10 density:      10.0
Log10 temperature:   5.5

  1           1s2.2s 2S1/2  1.00e-00
  2           1s2.2p 2P1/2  2.30e-07
  3           1s2.2p 2P3/2  4.52e-07
  4           1s2.3s 2S1/2  5.07e-11
  5           1s2.3p 2P1/2  7.26e-12
  6           1s2.3p 2P3/2  1.44e-11
  7           1s2.3d 2D3/2  5.30e-12
  8           1s2.3d 2D5/2  7.96e-12

IDL> show_pops,8,6,lev=-8,temp=[5.5,6.0],sum_mwl_coeffs=[0.75,0.25]

Log10 density:      10.0
Using a sum of Maxwellians

  1           1s2.2s 2S1/2  1.00e-00
  2           1s2.2p 2P1/2  2.26e-07
  3           1s2.2p 2P3/2  4.43e-07
  4           1s2.3s 2S1/2  8.93e-11
  5           1s2.3p 2P1/2  1.60e-11
  6           1s2.3p 2P3/2  3.16e-11
  7           1s2.3d 2D3/2  1.13e-11
  8           1s2.3d 2D5/2  1.69e-11

where it can be seen that the n=3 level populations are enhanced by factors  2 by the high temperature component to the distribution.

9.9  Looking at level populations

To plot the populations of the first 4 levels of Si III as a function of density at a temperature of 3 x 10⁴ K:

 IDL > plot_populations,'si_3',3.e+4,4 

Optionally, output files can be created.

Alternatively, SHOW_POPS can be used. This routine has a large range of features implemented via keywords.

9.10  Looking at the processes that populate each level

To assess the contributions of the different physical processes to the population of a specified level within an ion, use POP_PROCESSES.

 IDL> pop_processes,'fe_13',lev=4

Level:   3s2.3p2 1D2                   

Log10 Temperature:   6.2
Log10 Density:      10.0

Population leaving level 4
  rad. decay:     1.60e+01     42.50%
  e de-exc:       3.29e-01      0.87%
  e exc:          2.10e+01     55.88%
  p de-exc:       2.44e-01      0.65%
  p exc:          3.75e-02      0.10%
  stim. emiss:    0.00e+00      0.00%
  photoexc:       0.00e+00      0.00%
                  --------
           TOTAL  3.77e+01


Population entering level 4
  rad. decay:     3.50e+01     92.98%
  e de-exc:       3.38e-02      0.09%
  e exc:          1.47e+00      3.92%
  p de-exc:       2.81e-03      0.01%
  p exc:          1.13e+00      3.01%
  stim. emiss:    0.00e+00      0.00%
  photoexc:       0.00e+00      0.00%
                  --------
           TOTAL  3.77e+01

which shows that the level population is dominated by electron excitation and cascading into the level, and by radiative decay out of the level.

Note that the rates for each physical process are multiplied by the population of originating level (this results in the totals for entering and leaving the level to balance).

9.11  Searching for a line

If you want to list the lines within one ion around some wavelengths, you can use WHICH_LINE. For example,

IDL> which_line,'o_6',1032

     Wavelength   i   j  Lower level           Upper level             A-value
*      1031.914   1   3  1s2.2s 2S1/2        - 1s2.2p 2P3/2           4.28e+08
       1037.615   1   2  1s2.2s 2S1/2        - 1s2.2p 2P1/2           4.21e+08

Prints a list of atomic transitions and wavelengths for lines from O VI within 1% of the input wavelength (1032 Å).

9.12  Looking at the different ionisation equilibria

If you are interested to see the differences between the various ionisation equilibria for e.g. Mg, you can use:

 IDL > plot_ioneq,'Mg'

You will be able to select one of the files, and optionally create a postscript file of the plot.

If you are only interested in e.g. the Mg VIII, Mg IX, Mg X ions, you can type:

 IDL > plot_ioneq,'Mg', ion=[8,10]

If, instead, you are interested in obtaining the temperature at the maximum ionisation fraction for e.g. Mg X, you can use:

 IDL > print, max_temp ('Mg X')

You will be asked to select an ionisation equilibrium file.

9.13  Density and temperature diagnostics from line ratios

Spectroscopic diagnostic line ratios in the UV wavelength range have been used extensively to determine the electron density and temperature in the solar atmosphere (cf Dere and Mason, 1981, Gabriel and Mason, 1982, Mason, 1991, Mason and Monsignori Fossi, 1994). The theoretical intensity ratios from individual ion species provide a measurement of electron density which is independent of any assumptions about the volume of the emitting region. This is of particular importance in the transition region and coronal structures. The electron density (which determines the electron pressure) is an essential parameter in the study of energy transfer mechanisms. The routines that can be used are described below.

9.13.1  The DENS_PLOTTER and TEMP_PLOTTER widgets

DENS_PLOTTER and TEMP_PLOTTER are high-level widgets for the analysis of density- and temperature-sensitive ratios of lines from the same ion. They allow inclusion of proton rates and photoexcitation. The calling sequence is simple:

 IDL > dens_plotter,'o_5'

to study O V.

 IDL > temp_plotter,'c_4'

to study C IV.

Alternatively, you can use the command-line routines, DENSITY_RATIOS and TEMPERATURE_RATIOS. They also allow inclusion of proton rates and photoexcitation via KEYWORDS.

9.13.2  The DENSITY_RATIOS procedure

The routine DENSITY_RATIOS plots the variation of line intensities with electron density, allowing density diagnostics to be studied. As an example, we can look for density sensitive line ratios of O V in the 1000 to 1500 Å  wavelength region for densities between 10⁸ and 10¹³ cm^-3:

 IDL > density_ratios,'o_5',1000.,1500.,8.,13.,den,rat,desc

two windows will open and plot the relative intensities of a few O V lines. To choose the ratio of 1371.294 to 1218.393 Å line, select first the 1371.294 Å line. Another widget will appear to select the denominator. Select the 1218.393 Å line. This will chose the ratio of 1371.294 to 1218.393 which will be plotted in a new window. Values of the density and intensity ratio will be put into the variables den and rat and desc will contain a descriptive string.

 IDL >  print, desc 
 IDL > CHIANTI V. 4.0 O V 1371.2939 (Å)/1218.3929 (Å)  T = 2.51e+05 (K)

The DENSITY_RATIOS procedure also allows to calculate the ratio at user-defined value of constant temperature. Blends are accounted for via a selection of lines.

9.13.3  The TEMPERATURE_RATIOS procedure

To calculate temperature sensitive line ratios of C IV for lines between 100 and 1600 Å for temperatures between 10⁴ and 10⁶ K:

 IDL >   temperature_ratios,'c_4',100.,1600.,4.,6.,temp,rat,desc

As with density_ratios, a widget will appear that will allow you to select the numerator. Select the 384.175 and 384.190 Å lines as these will typically be blended in most spectrographs. Select the 1550.775 Å line for the denominator. The ratio of (384.175 + 384.190 Å) to the 1550.775 Å line as a function of temperature will be plotted and stored in the variables rat and temp, respectively. The TEMPERATURE_RATIOS procedure also allows to calculate the ratio at user-defined values of either constant pressure or constant density.

 IDL > print, desc
 IDL > CHIANTI V. 4.0 C IV 384.1750+384.1900 (Å)/1550.7750 (Å) Ne = 1.00e+10 (cm!e-3!n)

9.13.4  The CHIANTI_NE and CHIANTI_TE widgets

The IDL procedure which calculates line intensity ratios as a function of electron density is called CHIANTI_NE. Another IDL procedure to calculate ratios sensitive to electron temperature is called CHIANTI_TE. For example,

 IDL > chianti_te

Or

 IDL > chianti_ne

User interactions with the main widget setup the wavelength range and other parameters that are described individually below. On the left hand side are controls for wavelength and electron density or temperature selection and on the right hand side for ion selection.

Ion selection

Select first the element and then the ion stage using the pull-down menus. Only those elements and ions currently available in the CHIANTI database are displayed for selection.

Wavelength ranges

There are up to 4 wavelength ranges that can be defined in order to restrict the calculation (and the number of lines). At least one should be defined. Default is to calculate all lines from 1 to 1700 Å.

Electron Density/Temperature Range

For CHIANTI_NE, select the electron number density range (Log₁₀N_e) over which the intensity ratios are calculated. Default values are 10⁶ to 10¹⁴ cm^-3. The intensity ratios are calculated at constant temperature corresponding to the peak ionic abundance T_max, unless the value of the temperature is typed in.

For CHIANTI_TE, select the electron temperature (Log₁₀T_e) over which the intensity ratios are calculated. Default values are 10⁴ to 10⁸ K. The intensity ratios are calculated at a constant electron number density corresponding to 10⁸ cm^-3, unless a different value is typed in.

minimum intensity ratio

The relative intensity of all the lines found in the wavelength range is calculated. Only the lines that have an intensity (relative to the brighter one) greater than 0.0001 (by default) are selected and displayed.

Units for the ratio plot

The ratios can either be calulated from the relative intensities in ergs (default) or photons.

Controlling the procedure

The action of both CHIANTI_NE and CHIANTI_TE is controlled via the buttons in the central panel of the display. From left to right these are:

QUIT - click on this to exit from the program, all plot windows are also deleted.

CALCULATE LINE INTENSITIES - using the wavelength ranges as defined in the widgets above. Two plots will apear in the window - on the left the N_i*A/N_e and on the right the intensity ratios, where N_i is the level population and A is the radiative transition probability (s^-1). A list of spectral lines in the given wavelength range for that ion is displayed in the message window. The reference index is in the first column, then the wavelength, intensity and transition.

PLOT RATIO - prompts for and then plots specific line intensity ratios, using line indices available from the list. The ratios within a particular ion can be stored for later use using the SAVE button. To allow for blended lines in the observed spectra, multiple line indices can be given for the numerator and denominator. The format is fairly flexible but the nominator and denominator specification must be separated by a '/'. Otherwise the line indices can be separated by spaces or commas. The ratio values can be plotted either with a linear or a log scale.

HARDCOPY - the menu under this button will allow a variety of hardcopy plots (ratio plots or intensity plots) and the line details (+refs), which gives a record of the input. A line ratio has to be defined.

SAVE - it is sometimes useful to save the plotted line intensity ratios to study several different ions. You will be asked to enter file name to store ratio data. A line ratio has to be defined.

In the CHIANTI_NE case, a .CH_NE will be appended. An IDL structure called NE_RATIO will be saved. It has the TAGS: DENSITY,RATIO, TEMPERATURE, UNITS, COMMENT, DESC. The first two have the arrays of the densities and ratios, TEMPERATURE has the value of the constant temperature used, while the last three have a description of the units used, how the calculation was performed, and a description of the lines used to defined the ratio.

In the CHIANTI_TE case, a .CH_TE will be appended. An IDL structure called TE_RATIO will be saved. It has the TAGS: TEMP, RATIO, DENSITY, UNITS, COMMENT, DESC. The first two have the arrays of the temperatures and ratios, DENSITY has the value of the constant density used, while the last three have a description of the units used, how the calculation was performed, and a description of the lines used to defined the ratio.

Please note that previous versions of the above routines did not create the TEMPERATURE (DENSITY), UNITS, COMMENT tags.

The save file can be restored and replotted outside of CHIANTI_NE and CHIANTI_TE using the procedures PLOT_CHIANTI_NE and PLOT_CHIANTI_TE respectively, or used within user-defined procedures.

DELETE PLOT WINDOWS - to clear the ratio plots from the screen.

9.13.5  The PLOT_CHIANTI_NE and PLOT_CHIANTI_TE procedures

The ratio values stored in the save files created with the CHIANTI_NE and CHIANTI_TE routines can be replotted outside of CHIANTI_NE and CHIANTI_TE using the procedures PLOT_CHIANTI_NE and PLOT_CHIANTI_TE respectively. For example,

 IDL > plot_chianti_te

Or

 IDL > plot_chianti_ne

If no files are specified, a widget allows you to select any '*.CH_NE' or '*.CH_TE' files.

A LOG keyword allows the user to have the plot in a log scale.

It is also now possible to interactively modify the X and Y ranges and to create a postscript file. Users can modify these routines to e.g. over-plot observed data points.

9.13.6  Calculating temperatures by using different ions

Note: If you are interested in determining an isothermal temperature by using the ratio of lines emitted by different ions (and/or elements), then a possible way is to first calculte the contribution functions of the lines you are interested, and then calculate their ratio. Note, however, that such determinations can be very inaccurate, since they depend on the ionisation equilibrium chosen (and eventually on the element abundance).

9.14  Calculating contribution functions

To calculate the contribution function ( erg  cm³ s^-1 sr^-1 by default) vs. temperature at a specified abundance, ionization equilibrium and pressure or density for the Fe XXIV line at 255.1 Å:

 IDL >  gofnt,'fe_10',170.,180.,temperature,g,desc  

temperature, g are the arrays with the temperatures and the G(T) values. It is possible to calculate the G(T) at either constant electron density or pressure, via the KEYWORDS DENSITY or PRESSURE.

The KEYWORDS ABUND_NAME, IONEQ_NAME allow to run the routine in the background, giving names of the abundance and ionization fractions files.

The routine GOFNT allows the user to select a number of lines. If this is done, then the total sum of the G(T)'s of the selected lines is returned and plotted.

Optional outputs can be created. The default units are erg  cm³ s^-1 sr^-1, unless the KEYWORD /PHOTONS is set, in which case the units are photons  cm³ s^-1 sr^-1.

9.15  Calculating radiative losses

A procedure ('RAD_LOSS') calculates the total radiative loss rate as a function of temperature for specified set of abundances and/or ionization equilibria:

 IDL > rad_loss,temperature,loss_rate

9.16  The calculation of the DEM

Given a set of observed spectral intensities, the problem is to invert a system of integral equations like the previous one. The procedure CHIANTI_DEM solves the system and calculates the DEM(T).

The inversion problem itself is not simple and requires some assumptions about the nature of the solution. A series of workshops was sponsored in 1990/91 to study differential emission measure techniques (Harrison and Thompson, 1992). It was found that most codes eventually gave consistent results, but that the DEM derived depends rather critically on the methods used to constrain the solution and the errors in the observed intensities and atomic data.

It is advisable to select a number of well resolved, unblended lines which are not density sensitive, emitted by various elements over a wide temperature interval. Appropriate values of the pressure (or density) and the elemental abundances must be chosen according to the region of the Sun being observed. The pressure value can be obtained once the values of the temperature and the density are estimated. To estimate the electron density the procedure CHIANTI_NE can be used. The temperature can be estimated for example using the procedure CHIANTI_TE.

The contribution functions C (T,l_ij,N_e) can be calculated using CHIANTI_DEM either at constant pressure or at constant electron density. It is also possible to vary the elemental abundances before starting the fit to deduce the DEM.

Many papers have been written on solar elemental abundances. See e.g. Meyer (1993) Widing and Feldman (1992), Mason (1992, 1995). A possible approach in determining elemental abundances is to use the detailed shape of the DEM distribution for ions from the same element and apply an iterative procedure to normalize the curves for different elements (e.g. Fludra and Shmelz 1995, Del Zanna et al. 1995).

The CHIANTI_DEM procedure

The main IDL routine which has been written to perform a differential emission measure analysis of EUV spectra using the CHIANTI atomic database is CHIANTI_DEM. Other procedures required to run CHIANTI_DEM are GET_CONTRIBUTIONS , DEM_FIT, ZION2SPECTROSCOPIC and Z2ELEMENT. The resulting DEM may then be used by other procedures to calculate a synthetic spectrum.

This package of routines will be replaced in the future by new more versatile versions.

The main inputs required by CHIANTI_DEM are :

• the file with the observed fluxes. It can be selected using a widget-type browse from within CHIANTI_DEM or using the optional keyword FILE_INPUT='myfilename' . It must contain 5 columns of unformatted data ( separated by at least one space). The 5 fields are:

  1) the observed wavelength l_obs [Å].

  2) The observed flux I_obs in ergs  cm^-2 s^-1 sr^-1.

  3) The corresponding error s_obs on the flux in ergs  cm^-2 s^-1 sr^-1.

  4) The value of dl [Å]. All the theoretical lines that may have contributed to the observed lines, i.e. that have a theoretical wavelength l_theo in a l_obs ±dl range will be searched for. This value should correspond to the spectral resolution of the instrument at that wavelength.

  5) The identification, written as a string of up to 20 characters. For example:

  171.114 4811.0 1443.0 0.25 Fe IX

  174.604 4005.0 1202.0 0.25 Fe X

  180.448 3877.0 1163.0 0.25 Fe XI bl Fe X

  195.149 3443.0 1033.0 0.25 Fe XII

• the pressure N_e T  [cm^-3 K] or the density N_e  [cm^-3], passed to the routine via a keyword.
• the ionization equilibrium file, selected using a widget.
• the elemental abundances file. A selection of files are already stored in the CHIANTI package, but user-defined files in the working directory can also be used. Any *.abund file present in the CHIANTI database or in the working directory can be selected through a widget from within CHIANTI_DEM. The selected file can also be edited.
• An output file name must also be supplied via a keyword (e.g. OUTPUT= 'active_region'). Various files will be generated by CHIANTI_DEM having file names created by adding suffixes to the output file name.

Once the file with the observed fluxes is read, another IDL procedure, GET_CONTRIBUTIONS, is called by CHIANTI_DEM in order to calculate the contribution functions C(T,l_ij,N_e) at the given constant density or pressure.

GET_CONTRIBUTIONS searches the CHIANTI database for all the theoretical lines that may have contributed to the observed lines, i.e. that have a theoretical wavelength l_theo in a l_obs ±dl interval.

Then, for each theoretical line selected, it calculates the C values for the temperature interval log(T)= 4.0 - 8.0 in steps of log(T) = 0.1.

If a constant pressure is selected, for each ion the contribution function is calculated at an electron density N_e equal to the ratio of the pressure and the temperature of maximum ionization fraction.

The C(T) values are stored by GET_CONTRIBUTIONS in the output file output.contributions that can be used later, if required, to re-calculate the DEM, changing various parameters (e.g. the abundances), without having to start again and read the CHIANTI database, which can take a long time.

The observed lines with no theoretical counterparts are automatically excluded. If this happens, you might consider starting again with a larger dl, to see if there are theoretical lines in the vicinity of the observed one.

Then you are asked to select an *.abund file present in the CHIANTI database or in the working directory, and eventually edit it, if you want to change some abundances.

The G(T) are calculated, multiplying each theoretical line by the abundance factor. The theoretical lines contributing to each blend are sorted by intensity and then their G(T) can be plotted if the keyword PLOT_GT was activated. It is recommended to do this the first time, to check if there are some observed lines which are heavily blended with lines of other elements. It might be better to exclude such lines in a second run.

The G(T) for each blend are then summed and plotted, and the calculation of the DEM starts, using the fitting routine DEM_FIT. A series of parameters can change the result (DEM), especially the number and position of the mesh points of the spline that represents the DEM. The fitting procedure is based on Bevington's Data Reduction and Error Analysis for the Physical Sciences. fortran programs.

The iteration is controlled using key-words (see below).

A series of outputs are created, all having extensions of the output name. For example, using test as the output name:

• test.contributions: The first three lines contain the abundance file, the ionization equilibrium file names, and the constant value of the pressure or the density adopted. Each subsequent line contains the observed wavelength l_obs, the theoretical one l_theo, the element and ionization stage, the C(T) values and the specification of the transition.

• test.dem: Is the file where the DEM(T) values are written, in a format suitable for input to the CHIANTI_SS procedure which may be used to calculate a synthetic spectrum from the DEM.
• test.general: Is the file where general information is stored.

  The abundance file, the ionization equilibrium file and the pressure used are written at the beginning.

  Then there is one line for each observed line, with the identification present in the input file, the observed wavelength l_obs, the observed flux I_obs, the calculated flux I_theo , the error on the flux s_obs, the value ([(I_theo - I_obs)/(s_obs )] )² and finally the value of [(I_theo)/(I_obs)]

  After this line, there is one line for each theoretical line contributing to the blend, with the identification, the theoretical wavelength l_theo, the configuration and terms, and the contribution (as a percentage) of each line in the blend to I_theo.

• test.out: This file , toghether with test.dem, can be used to reproduce the results using user-written software. It contains: the identification present in the input file, the observed wavelength l_obs, the observed flux I_obs, the calculated one I_theo , the error on the flux s_obs, and the logarithmic values of the temperature and the DEM for each observed line. This temperature is the value where the product G(T)*DEM(T) has a maximum.
• three optional postscript files: test_gt.ps test_dem.ps test_4plots.ps .

  The first one has the G(T) of all the lines then used for the fit, with all the contributions for each line summed ( the labels refer to the identifiacation given in the input file).

  The file test_dem.ps has the DEM (T) with the scales set as in the interactive session. The points are plotted at the temperature where the product G(T)*DEM(T) has a maximum. It is possible to label the points with the comment string present in the input file, or to use the dominant ion in the blend.

  The file test_4plots.ps has some additional plots. The upper-right figure of test_4plots.ps plots the values [(I_theo)/(I_obs)] versus the temperature where G(T) has it's maximum.

• It is also possible to have postscript files of the G(T) functions, using the keyword PLOT_GT.

9.16.1  Controlling the procedure

The action of CHIANTI_DEM is controlled via the following keywords.

• FILE_INPUT: optional; if not set, you are prompted to select the observation file using a widget-type search.
• ARCSEC: optional set this if the intensities are specified in units per arcsec^-2.

  The default units are ergs  cm^-2 s^-1 sr^-1.

• PHOT: optional; set this if the intensities are specified in units per steradians^-1.

  The default units are ergs  cm^-2 s^-1 sr^-1.

• OUTPUT : required; the name for the output. Suffixes will be added to this name when creating the various outputs.
• FILE_GT: if not set, the routine GET_CONTRIBUTIONS is called. Either the pressure or the density must be set in this case.

  If set, it has to specify the name of the file previously created by GET_CONTRIBUTIONS, where all the contribution functions C(T) are stored.

• PRESSURE: the value of the pressure (Ne T). Required if you do not already have the contribution functions C(T) (i.e. if you do not set FILE_GT). Either the pressure or the density must be set in this case.
• DENSITY : the value of the electron density (Ne). Required if you do NOT already have the contribution functions C(T). Either the pressure or the density must be set in this case.
• CUT_GT: optional; if set, only those theoretical lines that have a MAX(C(T)) greater than the value set, are kept; it is useful to set this value in order to reduce the number of lines in the file where the C(T) are stored. If not set, a default value of 10^-30 is adopted.
• N_MATCHES: optional; in the unlikely event that more than 20 (default value for N_MATCHES) theoretical lines corresponding to an observed line are found, the routine stops. In this case, you have to start again setting N_MATCHES equal to a greater number.
• PLOT_GT: optional; if set, plots of the G(T) of the theoretical lines contributing to each observed line not excluded are created. It is possible to change the scale and create postscript files of these plots, interactively.
• EXCLUDE_OBS_WVL: optional; if set, has to be an array that specifies the wavelengths of the lines that you want to exclude from the fit. Note that even if you set this keyword and run GET_CONTRIBUTIONS all the theoretical lines found corresponding to all the lines in the input file are written in the C(T) file. It is only in the fit that the lines are excluded.
• MESH_POINTS: optional; it is an array that specifies the mesh points for the spline that represent the fitted DEM, in log(T). If not set, the default values [4,4.5,5,5.5,6,6.5,7,7.5,8] are assumed.
• N_ITER: optional; it is the maximum number of iterations of the fitting routine. If not set, a default value of 20 is assumed. Changing this value alone might not affect the fit, since the value of DCHISQ_M is monitored at each iteration to check for convergence.
• DCHISQ_M: optional; if not set, a default value of DCHISQ_M= 1 ·10^-5 is assumed. For each iteration, the c² and it's variation are calculated. As long as the iteration achieves a relative improvement in c² greater than DCHISQ_M , another iteration will be performed.
• DEM_FILE: optional; if set you are prompted to choose a DEM file to be used initially, instead of the default constant value of 10²². You can either choose one of the files in the CHIANTI database or any you have in the working directory. A plot of the DEM is created. The values in the file are marked as crosses, the mesh points are marked with triangles.
• QUIET: optional. Set to avoid various messages and the details of the result.

There are also some actions controlled via the keyboard.

When you are asked for an answer ( [y/N] ) yes or no you should either type in y or n. The capital letter in [y/N] means that the default choice is n which is what you get if you simply hit the return key. In case you have [Y/n], hitting the return key is the same as choosing y .

9.16.2  Examples

You must specify the output file name and the value of the pressure (or the density). The input file name is optional.

IDL > CHIANTI_DEM,OUTPUT='test',FILE_INPUT='test_obs',PRESSURE=1e16,/PLOT_GT

Select the ionization equilibrium file (e.g. Arnaud & Raymond). If there are no problems about N_MATCHES, the routine will select the lines having max( C(T) ) ³ 10^-30 and write the C(T) values to the file test.contributions.

Then you'll be asked to select an abundance file and if you want to edit it. Pick up the Feldman abundances. Then the G(T) are calculated, multiplying each theoretical line by the abundance factor, sorted (within each blend) by their max( G(T) ) value, and plotted ( see Fig. 8).

It is recommended that you check the plots at least once, to see if there are some observed lines that it might be better to exclude in a second run, for example because they are blends. Also check if your identifications are consistent with the lines found in the CHIANTI database.

The G(T) for each blend are then summed, and plotted ( see Fig. 9).

At the end of the fit, the files test.dem, test.general, test.out are created.

Have a close look at these outputs, and check if there are emission lines not well represented by the fit or with no theoretical counterparts.

You can use the routine a second time, excluding some of the lines, and/or varying some of the fitting parameters. In particular, changing MESH_POINTS or starting from an appropiate DEM can affect the resulting DEM. For example:

IDL> CHIANTI_DEM,OUT='test',FILE_IN='test_obs',FILE_GT='test.contributions', $
IDL> EXCLUDE_OBS_WVL=[ 284.153 ] ,$
IDL > MESH_POINTS= [ 4.85, 5.6, 6.25, 7.0 ],N_ITER=40

The files test.dem, test.general, test.out will be created.

Eventually, also the files test_dem.ps test_4plots.ps may be created.

Fig. 10 shows the resulting DEM. The error bars on the points simply reproduce the error on the observed fluxes.

The Fig. 11 is self-explanatory. The DEM figure is repeated in the upper-left plot with the same scale of the previous plot.

The file test.out , toghether with test.dem, can be used to reproduce these plots using user-written software. If the only concern is the postscript output, then users just have to copy the routine in the working area and modify the top procedure PRINT2D_PLOT.PRO that controls the postscript device. The default is landscape.

9.16.3  Some final remarks

This package is mostly intended to be a quick method to obtain a DEM which can then be used to calculate a synthetic spectrum, to be compared with the observed data.

Try to give as input lines covering a broad range in temperatures, and that are not density sensitive.

Try to adjust the location of the mesh points.

If the resulting DEM does not give a good fit to the data, it might be a good idea to start again calculating the G(T) with different abundances or to check the effect of blends.

Try a different DEM as a starting point, but be careful about the end points at lower and higher temperatures where usually there are no constraints (no observed lines).

Consider the possible effect on the DEM of different structures along the line of sight. It is important to realise that the DEM gives an indication of the amount of plasma at different temperatures along the line of sight, assuming constant density or pressure. It is not therefore possible to infer direct information about the variation of the temperature with height from this function. The inclusion of density-sensitive lines in the fit may also cause problems.

Send comments to : Giulio Del Zanna   g.del-zanna@damtp.cam.ac.uk

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A  Description of the CHIANTI V.4 software updates

A.1  Routines already available in Version 3

The previous routines have been modified as described:

• ascii_wvl_dem.pro creates an ascii file with a list of line identifications and intensities.

  Compared to the previous version, these are the main changes:

  1-Rewritten as a wrapper routine using the new procedures.

  2-Now the PRESSURE value is a keyword.

  3-The calculations can be done at constant DENSITY.

  4-Energies (keV) can be output instead of wavelengths in Angstroms

  5-MASTERLIST can now be used both as an input string or as a keyword.

• latex_wvl_dem.pro creates a latex file with a list of line identifications and intensities.

  Compared to the previous version, these are the main changes:

  1-Rewritten as a wrapper routine using the new procedures.

  2-Now the PRESSURE value is a keyword.

  3-The calculations can be done at constant DENSITY.

  4-MASTERLIST can now be used both as an input string or as a keyword.

• synthetic.pro Calculates a synthetic spectrum. It outputs arrays.

  Compared to the previous SYNTHETIC, these are the main changes:

  1-Rewritten as a wrapper routine using the new procedures.

  2-Now the PRESSURE value is a keyword as the DENSITY value

  3-The keyword CONT is now renamed CONTINUUM

  4-Added keywords

  
  PHOTONS   (If set, intensities are in photons instead of ergs)
  
  DEM_NAME, ABUND_NAME, IONEQ_NAME,  to run the routine in the 
                                     background, giving names of the
                                     DEM, abundance and ionization
                                     fractions files.
  
  NOPROT (If set, then proton rates are not included.)
  
  RADTEMP, RPHOT (to include photoexcitation)
  
  
  

  5-MASTERLIST can now be used both as an input string or as a keyword.

  6-The description of the line details now has the spectroscopic designation at the end.

• synthetic_plot.pro plots the spectrum and interactively identify lines

  Is left unchanged except for a few minor changes.

• gofnt.pro calculates the contribution functions

  Aside from a few small fixes, these are the main changes:

  1-Rewritten as a wrapper routine using the new procedures.

  2-Added keywords

  
  ABUND_NAME, IONEQ_NAME,  to run the routine in the 
                                     background, giving names of the
                                     abundance and ionization
                                     fractions files.
  
  NOPROT (If set, then proton rates are not included.)
  
  RADTEMP, RPHOT (to include photoexcitation)
  
  
  

• isothermal.pro Calculates line intensities with an isothermal approximation.

  Compared to the previous routine, these are the main changes:

  1-Rewritten as a wrapper routine using the new procedures.

  2-Added keywords

  
  ABUND_NAME, IONEQ_NAME,  to run the routine in the 
                                     background, giving names of the
                                     abundance and ionization
                                     fractions files.
  
  NOPROT (If set, then proton rates are not included.)
  
  RADTEMP, RPHOT (to include photoexcitation)
  
  EM      Emission measure values.
  
  
  

• chianti_ss.pro Widget for creation of SOHO synthetic spectra.

  Is not distributed nor supported anymore. Is now replaced by ch_ss.pro

• plot_populations plots the level populations

  Compared to the previous routine, these are the main changes:

  1-Modified the plotting, adding information about the single lines.

  2-Added keywords

  
  NOPROT (If set, then proton rates are not included.)
  
  RADTEMP, RPHOT (to include photoexcitation)
  
  
  

• density_ratios plots the variation of line intensities with electron density

  Compared to the previous routine, these are the main changes:

  1-Rewritten as a wrapper.

  2-Added keywords

  
  NOPROT (If set, then proton rates are not included.)
  
  RADTEMP, RPHOT (to include photoexcitation)
  
  
  

• temperature_ratios plots the variation of line intensities with electron temperature

  2-Added keywords

  
  PHOTONS   (If set, intensities are in photons instead of ergs)
  
  IONEQ_NAME The ionization fractions file.
  
  NOPROT (If set, then proton rates are not included.)
  
  RADTEMP, RPHOT (to include photoexcitation)
  
  
  

• freefree calculates the free-free (bremsstrahlung) continuum

  The call is the same, but the calculations are done using the fitting formulae of Itoh et al. (ApJS 128, 125, 2000) and Sutherland (MNRAS 300, 321, 1998). Also, a few bugs have been fixed.

• freebound.pro calculates the free-bound continuum

  Added the keyword

  PHOTONS (If set, intensities are in photons instead of ergs)

• rad_loss.pro calculates the radiative losses

  -Added keywords

  
  NOPROT (If set, then proton rates are not included.)
  
  RADTEMP, RPHOT (to include photoexcitation)
  
  
  

A.2  Other routines that were previously available only within SolarSoft

These routines are in the other/ subdirectory:

• max_temp.pro Calculates temperature at max ionisation ratio for an ion

  Unchanged.

• plot_ioneq.pro Plots the ionisation equilibrium values for an element.

  Unchanged.

• chianti_ne.pro Calculate and plot density sensitive line ratios.

  Widget unchanged but the low-level routine now uses emiss_calc.pro.

• plot_chianti_ne.pro Plots a density sensitive ratio saved from CHIANTI_NE

  Unchanged.

• chianti_te.pro Calculate and plot temperature sensitive line ratios.

  Widget unchanged but the low-level routine now uses emiss_calc.pro.

• plot_chianti_te.pro Plots a temperature sensitive ratio saved from CHIANTI_TE

  Unchanged.

• chianti_dem.pro Calculates the Differential Emission Measure DEM(T) using the CHIANTI database, from a given set of observed lines.

  Changed the low-level routine that calculates the G(T), to account for the v.4 variations. The proton rates are included in the calculation of the level population.

• plot_dem.pro To plot differential emission measure (DEM) values

  Unchanged.

Routines in the extra/ subdirectory:

• dens_plotter.pro A widget routine to allow the analysis of density sensitive ratios.

  Is now a wrapper routine calling the widget RATIO_PLOTTER

• temp_plotter.pro A widget routine to allow the analysis of temperature sensitive ratios.

  Is now a wrapper routine calling the widget RATIO_PLOTTER

• g_of_t.pro To compute the G(T) of selected lines.

  A few keywords have been added/ modified, mainly as an update for V.4.

• pop_plot.pro To plot n_j A_ji / N_e values as a function of N_e

  A few keywords have been added/ modified, mainly as an update for V.4.

• show_pops.pro To display populations of significant levels in a CHIANTI ion model

  A few keywords have been added/ modified, mainly as an update for V.4.

• emiss_calc.pro To compute the emissivities of all lines of a specified ion over given ranges of temperature and density.

  A few keywords have been added/ modified, mainly as an update for V.4.

• integral_calc.pro To compute the atomic data integral for use in column or volume emission measure work.

  A few keywords have been added/ modified, mainly as an update for V.4.

B  Incorporating proton rates into CHIANTI

This section describes the changes applied to the CHIANTI database and software in order to include the proton rates.

B.1  The proton rate data files

The proton rate data files have suffices .psplups and have the following format

  2  3  2 0.000e+00 1.027e-02 8.000e+02-2.150e-13 1.052e-13 4.397e-12 \
2.232e-11 5.389e-11 8.708e-11 1.014e-10 7.658e-11-2.805e-12

(The \ indicates a break in the line.) Note that the Z and spectroscopic number are not given for each ion, in contrast to the electron files. The rest of the line is the same as that for the electron files, except in this case there are 9 spline values as a 9-point spline was fitted to the data.

B.2  Reading the .psplups file

This is done by the routine read_splups.pro which loads the data into an IDL structure. The call is

      IDL> read_splups_ns, filename, splstr, splref , /prot

The structure splstr has the following tags

      .lvl1   lower level index
      .lvl2   upper level index
      .t_type transition type
      .gf     gf value
      .de     Delta-E for transition (rydbergs)
      .c_ups  the scaling parameter
      .nspl   number of spline points
      .spl    Vector of length 9, containing spline points

B.3  Changes to pop_solver.pro

The routine pop_solver solves the set of linear equations that determine the level balance of the ion. To include proton rates, an extra matrix containing the proton rate coefficients needs to be added to the equations. This matrix is created within pop_solver from the splstr structure mentioned above.

Note also that the same routine is used to descale the spline fits into proton rates as to descale the electron spline fits. This routine is descale_all.pro and is called as

      descale_all, temp, splstr, index, ups

where temp can be an array of temperatures.

B.4  Implementing proton rates in user-written routines

User-written routines can be modified to include proton rates through two steps.

For routines which do not directly call pop_solver, the only changes are to add the keywords noprot=noprot, abund_file and ioneq_file to the routines' argument list, and to the call to the routine that calls pop_solver.

For routines that directly call pop_solver, the following steps need to be followed.

The first is to add the keyword noprot=noprot to the routine's argument list.

The second is to add a common block analogous to those that already exist for the energy level, radiative and electron collision data. This common block is

      COMMON proton, pstr, pe_ratio

The third step is to add a line which will read the data. This is

      if keyword_set(noprot) then begin
        pstr=-1
      endif else begin
        read_splups, pname, pstr, pref, /prot
      endelse

Before the call to pop_solver, the proton to electron ratio must be evaluated. This is done with

      pe_ratio=proton_dens(temp)

where temp contains the logarithm of the temperatures that will be passed to pop_solver.

B.5  The proton-to-electron ratio

To include the proton rates in CHIANTI it is necessary to know the proton number density N_p. This quantity is usually expressed in terms of the ratio relative to the electron density. For a standard solar plasma this is a constant for temperatures beyond log T=4.6 with a value around 0.85. Thus one option is to simply fix the ratio as a constant.

As we want CHIANTI to be applicable for low temperature plasmas, however, we have decided to explicitly calculate the ratio making use of the ion balance and abundance files, that uniquely determine N_p. The relevant routine is PROTON_DENS.PRO. N_p is calculated from the ion balance and element abundance files contained in CHIANTI through the following expression

R(T) =  Np Ne =   Ab(H) F(H+,T) n å i=1  i å Z=1  Z F(Ai+Z, T) Ab(Ai)

(37)

where Ab is the element abundance, A_i is the ith element (i.e., A₁=H, A₂=He, etc.), Z is the charge on the ion, F(A_i^+Z, T) is the fraction of ions of element A_i in the form A_i^+Z at temperature T.

The ion fractions contained in CHIANTI are tabulated over the range 4.0 £ log T £ 8.0. Above and below these values, we set R(T) to the values for log T=8.0 and log T=4.0, respectively.

The use of this routine has some side effects. Some routines for which the ratio may have some effects in the results don't require you to select the ion balance or abundance files. E.g., DENSITY_RATIOS.PRO does not require the user to select these files, however, at low temperatures one may see significant changes take place in line ratios on account of the change in the proton-to-electron ratio. We deal with this effect by using the default !abund\_file and !ioneq\_file files to derive the proton-to-electron ratio, but allowing the files to be directly specified by the user through keywords if he/she needs to do this.

B.5.1  Implementing proton rates in user-defined procedures

We have modified the CHIANTI routines so as PROTON_DENS.PRO is called once at the beginning of the routine and the ratio data are passed to POP_SOLVER.PRO through a common block.

The modifications due to the proton-to-electron ratio in user-defined procedures are as follows:

• Extend the PROTON common block to include ratio data.

  common proton, pstr, pe_ratio
  
  

• If the ELEMENTS common block does not already exist in the routine, then it must be added

  COMMON elements,abund,abund_ref,ioneq,ioneq_t,ioneq_ref
  
  

• Call PROTON_DENS.PRO to get the ratio

  pe_ratio=proton_dens(temp)
  
  

The call to PROTON_DENS.PRO thus does not take place within POP_SOLVER.PRO

C  Incorporating 9 point spline fits into user-defined procedures

This section describes the changes in the IDL software required to incorporate the 9-point spline fits.

C.1  Data file format changes

The modification to the .splups file is simple. Any transitions which are fitted with a 9-point spline will simply have four extra numbers placed on the end of the data line. Transitions fitted with a 5-point spline will be output as normal. Both 5 and 9-point fits can be found in the same .splups file.

C.2  Changes to existing software

This section describes the changes to the read_splups routine, and also the changes required to routines that call directly or indirectly read_splups.

For some routines (such as synthetic, ...?) the reading of the data files is delegated to the routine setup_ion.pro. The data is then transferred to the main routine via common blocks.

C.2.1  Routines that call read_splups

Every routine that makes a call to read_splups.pro has to be modified. Two changes are needed:

1. the call to read_splups
2. the upsilon common block which contains the spline data

The read_splups call used to be

      read_splups,upsname,t_type,gfu,deu,c_ups,splups,upsref

The new call is

      read_splups, filename, splstr, splref [, /prot]

where /prot should be set if proton rates are to be read.

The original common block had the form

      COMMON upsilon,t_type,deu,c_ups,splups

The new one should be

      COMMON upsilon, splstr

C.2.2  read_splups

This reads data from .splups or .psplups files into an IDL structure (the previous version read data into several individual arrays). The call is

      IDL> read_splups, filename, splstr, splref [, /prot]

The structure splstr has the following tags

      .lvl1   lower level index
      .lvl2   upper level index
      .t_type transition type
      .gf     gf value
      .de     Delta-E for transition (rydbergs)
      .c_ups  the scaling parameter
      .nspl   number of spline points
      .spl    Vector of length 9, containing spline points

C.2.3  descale_all.pro

This routine directly replaces descale_ups.pro in the CHIANTI software. It is called as

      descale_all, temp, splstr, index, ups

An important difference is that the temperature is specified directly whereas previously the scaled temperature was given. In addition, several temperatures can be given at once rather than just one.

Note that there is no difference in how this routine treats the descaling of proton rates.

The only place in the CHIANTI software where this routine is called is in pop_solver.pro.

C.2.4  pop_solver.pro

The way electron excitation rates are included in pop_solver has been changed. Only a single for loop is required now as the routine goes through each line in the structure. In addition, the routine can now descale the upsilons for several temperatures simultaneously.

D  The extra set of complementary routines

This section describes the features of the routines that are contained in the extra/ directory and that were contributed by Peter Young:

• dens_plotter.pro A widget routine to allow the analysis of density sensitive ratios.
• temp_plotter.pro A widget routine to allow the analysis of temperature sensitive ratios.
• g_of_t.pro To compute the G(T) of selected lines.
• pop_plot.pro To plot n_j A_ji / N_e values as a function of N_e
• show_pops.pro To display populations of significant levels in a CHIANTI ion model
• emiss_calc.pro To compute the emissivities of all lines of a specified ion over given ranges of temperature and density.
• integral_calc.pro To compute the atomic data integral for use in column or volume emission measure work.

These routines, described in more detail in Sect. D.2 below, have slightly different units of outputs, compared to the other routines.

D.1  Definitions

First of all, Sect. 8 gives the theory behind the interpretation of optically-thin emission lines which serves to set out the notation used here. Going back to Eq. 2, we write

Ni=0.83 F(T) Ab(X) Ne ni,

(38)

where F(T) is the ionisation fraction (independent of N_e in current ion balance calculations), Ab(X) the abundance of the element relative to hydrogen, and the ratio of hydrogen to free electrons has been taken as 0.83, as hydrogen and helium are completely ionised for temperatures T > 10⁴ K.

The emissivity of the emission line resulting from a j-to-i radiative decay is defined as

eij = DE Nj Aji

(39)

and has units of erg cm^-3 s^-1. Often the alternative notation e_l will be used where l is the wavelength of the emitted radiation in Angstroms (Å), and l = 1.986×10^-8/DE for DE in ergs. We will also define the ion emissivity as

eij = DE nj Aji.

(40)

In order to relate the emissivity to the actual observed intensity of a line, we make use of the third assumption, which tells us that the intensity is proportional to the emissivity of the plasma, and so

Pl = ó õ el dV,

(41)

where P_l is the power in an observed line (units: erg s^-1), and dV is a volume of plasma with temperature T and density N_e.

Expanding e_l using Eqs 38 and 39 gives

Pl = 0.83 DE Ab(X) ó õ F(T)  nj Aji Ne dV.

(42)

An important feature of emission measure studies is to isolate those lines for which n_j A_ji ~ N_e. By analysing only such lines, we are essentially separating the determination of the emission measure from the determination of the plasma density. If the lines all had different density dependencies, then it would be necessary to determine the density variation with temperature before finding the emission measure. If the n_j A_ji ~ N_e relation is assumed then we write

Pl = DE Ab(X) ó õ Gl(T) Ne2 dV

(43)

where

Gl(T)=0.83 F(T)    nj Aji Ne

(44)

which is the so-called `G-of-T' function.

On account of the ionisation fraction F(T) this function is sharply peaked, and a common approximation (e.g., Pottasch [3], Jordan & Wilson [1]) is to assume that G(T) has a constant value over a narrow temperature interval around G(T_max), where T_max is the temperature of maximum ionisation for the ion. Here we will use the temperature of maximum emission or T_mem which is the temperature at which G_l has its maximum. Defining

Gl,0(T) = ì ï ï í ï ï î Cl |log T - log Tmem| < 0.15 0     |log T - log Tmem| > 0.15

(45)

we require that

ó õ Gl(T) dT = ó õ Gl,0(T) dT

(46)

so

Cl= ó õ Gl(T) dT Tmem(100.15 - 10-0.15) .

(47)

Our expression for P_l thus becomes

Pl = DE  Ab(X) Cl EM(V)

(48)

where

EM(V) = å i  æ è ó õ Vi  Ne2 dV ö ø

(49)

is the volume emission measure. Each volume V_i contains plasma with temperatures such that |log T - log T_mem| < 0.15, and the sum over i is required in case there are distinct regions along the line of sight that satisfy this condition on T.

Now, solar emission lines are often measured as intensity (or radiance), I, with units typically of erg cm^-2 sr^-1 s^-1. This quantity is related to P_l by

Pl = 4p ó õ I dA

(50)

where dA is the projected area of the emitting element. One thus relates the observed intensity to an emission measure by

4pI = DE  Ab(X) Cl EM(s)

(51)

where EM(s) is the column emission measure, where s is the line-of-sight depth of the emitting region.

Stellar emission lines are measured in flux (or irradiance), E, with units typically of erg cm^-2 s^-1. E is related to P_l by

Pl = 4pd2 E

(52)

where d is the distance to the object. The observed flux is then related to the emission measure by

E=  1 4pd2 DE  Ab(X) Cl EM(V).

(53)

If one treats the emitting region as a uniform, spherical shell of thickness h then dV=4pR²dh (R the distance from the star centre of the shell; typically R=R_*, the radius of the star) and so the expression for E becomes

E=  1 2  R*2 d2 DE  Ab(X) Cl EM(h).

(54)

where EM(h) is the emission measure over height. The factor 1/2 denotes that half the photons from the shell are emitted towards the stellar surface and so are destroyed. Jordan and co-workers (see, e.g., Jordan & Wilson [1], Jordan & Brown [2]) utilise this definition and an assumption of spherical symmetry to deduce energy balance relations in solar and stellar atmospheres.

D.2  The primary routines

The routines are divided into primary and secondary routines. The secondary ones are called by some of the primary routines, and chances are that you won't have to use them too often. They are described in Sect. D.3.

All of the routines have headers which give more detailed information about how they work. This header can be read in the normal IDL way through, e.g., doc_library,'ratio_plotter'.

D.2.1  pop_plot.pro

Example: For Fe XIII, select a line/blend from lines in the range 200 to 205 Å 

    pop_plot,26,13,wrange=[200,205]

Note how no single line shows zero density dependence, and so care should be taking in using Fe XIII in emission measure analyses. Compare with Fe XVI:

    pop_plot,26,13,wrange=[330,370]

where both the 335 and 360 lines are OK.

D.2.2  integral_calc.pro

This routine calculates C_l, defined in Eq. 47. It displays both this value and the values of DE C_l and 4p/ DE C_l. For lines for which n_jA_ji ~ N_e, C_l is insensitive to N_e, but for other lines N_e should be specified. Note that for blended lines only åDE C_l and 4p/ åDE C_l are output. The routine also outputs the T_mem of the lines, accurate to 0.02 dex.

Example: Work out C_l for the Fe XIII lines between 200 and 205 Å at a density of 10⁹ cm^-3.

    integral_calc,26,13,wrange=[200,205],dens=9.

From Eq. 51, an observed line intensity of 100 erg cm^-2s^-1sr^-1 for the 202.044 line implies a column emission measure of EM(s) = 100 ×1.614 ×10²⁰ / Ab(Fe), where 1.614 ×10²⁰ is taken from 4pi/DE*C_lambda column of the output.

For Fe XIV, one can do:

    integral_calc,26,14,wrange=[210,220],dens=9.

and so to get the same column emission measure for Fe XIV l211.32, an intensity of 100 ×1.614 ×10²⁰ / 2.280 ×10²⁰ = 70.8 erg cm^-2s^-1sr^-1 is required, where 2.280 ×10²⁰ is the value of 4pi/DE*C_lambda for Fe XIV l211.32.

D.2.3  temp_plotter.pro and dens_plotter.pro

Both temp\_plotter.pro and dens\_plotter.pro call a widget-based routine (ratio_plotter, via the keywords /temp and /dens) that allows the thorough investigation of density or temperature sensitive ratios. Observed line intensities can be input for line ratios, and densities or temperatures derived.

Example: to study density sensitive ratios of Fe XIII, simply type in

    dens_plotter,'fe_13'

Try inputting some line intensities and errors from the SERTS-89 spectrum (Thomas & Neupert [4]), and comparing the derived densities with those found by Young, Landi & Thomas [5] in Table 20.

D.2.4  show_pops.pro

Gives percentage level populations for all levels within the specified ion that have populations greater than 0.01%.

Example: Compute level populations for Fe XIII at a density of 10¹⁰ cm^-3:

    show_pops,26,13,dens=10

D.2.5  g_of_t.pro

Eq. 44 gives the definition of the contribution function as calculated by the g_of_t routine. In it's default setting g_of_t.pro actually calculates:

DE Gl(T)=0.83 DE F(T)    nj Aji Ne

which is more useful when considering blends of lines at different wavelengths. The DE can be `disabled' with the /no_de keyword. It is also useful to multiply the above function by the element abundance, and this is accomplished with the /abund keyword. The output function is tabulated over 4.0 £ log T £ 8.0 at 0.1 dex intervals. For smaller intervals, see the ion_interp routine.

Examples:

    result=g_of_t(26,13,dens=9.)
    result=g_of_t(26,13,wrange=[200,205],/abund)
    result=g_of_t(26,13,/no_de)

One can also use this routine to derive the T_mem of the emission line, by way of the ion_interp.pro routine, e.g.,

    result=g_of_t(26,13,dens=9.)
    ion_interp,t,result,ti,g_ti,10
    print,ti(where(g_ti eq max(g_ti)))

result is tabulated at 0.1 dex intervals in temperature. ion_interp interpolates result and in this case gives it at 0.01 dex intervals.

D.3  The secondary routines

These routines are called by the routines above.

D.3.1  emiss_calc.pro

Calculates the ion emissivity (Eq. 40) for all transitions within the CHIANTI model of the ion. The returned data is in the form of a structure. The default is to calculate emissivities for temperatures T_max and log T_max±0.15, and densities log N_e=8.0, 8.5, 9.0,....,12.0.

Example:

    emiss=emiss_calc(26,13)

D.3.2  emiss_select.pro

Allows the selection of lines/blends from the emiss structure created by emiss_calc.pro. This routine is useful if you want to access the emissivities of lines directly, e.g.,

emiss=emiss_calc(26,13)
em202=emiss_select(emiss,wra=[200,205],sel_ind=sel_ind)

D.3.3  ion_interp.pro

When reading the ionisation equilibrium files, you will receive an array with absolute (as opposed to log) ion fractions tabulated at 0.1 dex intervals from log T = 4.0 to 8.0. A common need is to interpolate this data and obtain the ion fraction tabulated at smaller intervals. As the ion fractions are generally sharply peaked, normal interpolation will lead to negative ion fractions at several temperatures, and so a more satisfactory method is to interpolate the log of the ion fraction. However, you need to take the log of only the non-zero values of the ion fraction.

The several lines of code required to perform the interpolation are straightforward but irritating (when typed on many occasions!), and so this routine performs the task.

Example: Use g_of_t to create a G(T) function for one of the Fe XIII lines,

    result=g_of_t(26,13,dens=9.)
    ion_interp,t,result,ti,g_ti,5

The G(T) function is now tabulated at 0.02 dex intervals. Note that if t is not specified, it is assumed to be a vector going from 4.0 to 8.0 in 0.1 dex intervals.

E  More details

More details are found in the program headers (see the html version of this guide).

E.1  The CHIANTI line intensities structure

The tags of the line intensities structure are:

       .lines     A structure containing information about the lines. 
                  Its size is the number of lines in the spectrum. The 
                  tags are:

                  .iz     The atomic number of the elements (e.g., 26=Fe)

                  .ion    The ionisation stage (e.g., 13=XIII)

                  .snote  The identification of the ion (e.g., 'Fe XXIV d')

                  .ident  The identification of the transition, configuration
                           and terms in text form.

                  .ident_latex
                          The identification of the transition, configuration
                           and terms in latex form.

                  .lvl1   The lower level of the transition (see .elvlc 
                          file for ion)

                  .lvl2   The upper level for transition.

                  .tmax   The temperature of maximum emission of the line.

                          If the G(T) are output, tmax is the maximum of G(T).

                          If the isothermal approximation is used  tmax=0.

                          If a DEM is used,  tmax is the maximum of the 
                          emissivity that includes the product of the ion
                          fraction and the DEM.
                          Rounded to nearest 0.1

                  .wvl    Wavelength of the transition, in Angstroms.

                  .flag   A flag, =-1 if the line has only theoretical energy
                          levels. Otherwise flag=0.

                  .int    Intensity of line (erg/cm2/s/sr or phot/cm2/s/sr), 
                          divided by the element abundance (exclusive with .goft). 

                  .goft   The G(T) of the line (optional /exclusive with .int).


       .ioneq_name     The ion balance file used (full path).
       .ioneq_logt        The Log10 T values associated.
       .ioneq_ref      The references.

       .dem_name       The differential emission measure file eventually  used
                       (full path).
       .dem            The Log10 DEM values 
       .dem_logt          The Log10 T values associated.
       .dem_ref        The references.

       .model_name    A string indicating the model used: 

                    1- Constant density
                    2- Constant pressure
                    3- Function (Te,Ne)

       .model_file    Full path of the (Te,Ne) file if defined. Null string otherwise.

       .model_ne    the Ne value(s).

                     - a scalar if 'Constant density' is selected.
                     - an array if 'Function' is selected.
                     - 0. if constant pressure is selected.

       .model_pe    the Pe value.

                     - a scalar if constant pressure is selected.
                     - 0. if 'Constant density' is selected.
                     - an array=density*temperature if 'Function' is selected.
                          
       .model_te    the Te values if 'Function' is selected. Otherwise 0.

       .wvl_units  The wavelength units.

       .wvl_limits    The wavelength limits specified by the user.

       .int_units  The intensity units (erg/cm2/s/sr or phot/cm2/s/sr) if
                  intensities are calculated, otherwise the G(T) units 
                  (erg cm3/s/sr or phot cm3 /s/sr)

       .logt_isothermal
                  The Log10(T) values used. 

       .logem_isothermal
                  The Log10(EM) values used. 

       .date      The date and time when the structure was created.

       .version   The version number of the CHIANTI database used.

       .add_protons 
                  A flag (0/1) to indicate whether proton data were used (1)
                  or not (0) to calculate the level population.

       .photoexcitation
                  A flag (0/1) to indicate if photoexcitation was included (1)
                  or not (0).

       .radtemp 
                 The blackbody radiation field temperature used (if
                 photoexcitation was included).

       .rphot
              Distance from the centre of the star in stellar radius units  
              (if photoexcitation was included).

E.2  The CHIANTI spectrum structure

The spectrum structure output of MAKE_CHIANTI_SPEC has the following ADDITIONAL tags (compared to the tags of the CHIANTI line intensities structure created by CH_SYNTHETIC:

                     LAMBDA      The array of X-values
                     SPECTRUM    The array of Y-values
                     UNITS       The units of LAMBDA, SPECTRUM
                     WRANGE      The wavelength range
                     INSTR_FWHM  The Instrumental FWHM
                     BIN_SIZE    Width of the Bins  (fixed) in angstroms
                     ABUND_NAME  The CHIANTI abundance file name             
                     ABUND       The abundance values
                     MIN_ABUND   The minimum abundance value used                 
                     ABUND_REF   The references
                     CONTINUUM   The values of the continuum (if calculated)                 
                     FILE_EFFAREA The Effective Area File used (optional)
                     EFFAREA       The array of effective area values
                                   (optional - same size of LAMBDA)

                    .LINES      An array of structures, for all the lines used               
                                to calculate the SPECTRUM. 
                                The tags are the same as those created by 
                                CH_SYNTHETIC, plus
                       .PEAK    The peak intensity of the line in the spectrum
                                (approx. value) 

F  List of main CHIANTI routines with description and headers

Synthetic spectra
• CH_SS
  Widget-based multi-purpose routine to calculate CHIANTI line intensities and continua, to create a synthetic spectrum, to make tables of lines, etc.
  
• CH_SYNTHETIC
  to calculate CHIANTI line intensities or G(T) and output an IDL structure.
  
• SYNTHETIC
  calculates a synthetic spectrum
  
• SYNTHETIC_PLOT
  to plot out synthetic spectra calculated with Synthetic and interactively identify spectral lines
  
• ISOTHERMAL
  Computes spectra from isothermal plasmas. A number of isothermal plasmas can be included. Note that this routine has a number of unique features that distinguish it from the other CHIANTI synthetic spectra routines. See the Programming Notes section.
  
• MAKE_CHIANTI_SPEC
  To create a CHIANTI synthetic spectrum
  Line intensities
• ASCII_WVL_DEM
  create an ascii file of predicted spectral line intensities and wavelengths corresponding to a selected abundance and differential emission measure (DEM).
  
• LATEX_WVL_DEM
  create a latex file of predicted spectral line intensities and wavelengths corresponding to a selected abundance and differential emission measure (DEM)
  
• CH_LINE_LIST
  Create a latex or an ascii file of predicted spectral line intensities and wavelengths corresponding to selected parameters, as calculated by CH_SYNTHETIC. Needs as input the line intensity structure calculated by CH_SYNTHETIC (default) or the SPECTRUM structure output of MAKE_CHIANTI_SPEC.
  Line emissivities
• EMISS_CALC
  To compute the emissivities of all lines of a specified ion over given ranges of temperature and density.
  
• GOFNT
  calculate G(n,T) function (line intensity per unit emission measure)
  
• G_OF_T
  To compute DE * F(T) * n_j * A_ji / N_e for selected emission lines. Option to also multiply by abundance.
  Density- and temperature-sensitive line ratios
• DENS_PLOTTER
  A widget-based routine to allow the analysis of density sensitive ratios. **** See RATIO_PLOTTER for details. *****
  
• DENSITY_RATIOS
  to calculate line intensity ratios as a function of electron density
  
• CHIANTI_NE
  Calculate and plot CHIANTI density sensitive line ratios. Explanation : CHIANTI_NE (density ratios) calculates and plots density sensitive line ratios based on the CHIANTI atomic database of Dere et. al.
  
• PLOT_CHIANTI_NE
  Plots a density sensitive ration saved from CHIANTI_NE Explanation : The routine CHIANTI_NE allows the calculated ratio to be saved in an IDL save file. This routine retrieves and plots the ratio.
  
• TEMP_PLOTTER
  A widget-based routine to allow the analysis of temperature sensitive ratios. **** See RATIO_PLOTTER for details. *****
  
• TEMPERATURE_RATIOS
  calculate and display temperature sensitivity of line intensity ratios
  
• CHIANTI_TE
  Calculate and plot CHIANTI temperature sensitive line ratios. Explanation : CHIANTI_TE (temperature ratios) calculates and plots temp. sensitive line ratios based on the CHIANTI atomic database of Dere et. al.
  
• PLOT_CHIANTI_TE
  Plots a temperature sensitive ratio saved from CHIANTI_TE Explanation : The routine CHIANTI_TE allows the calculated ratio to be saved in an IDL save file. This routine retrieves and plots the ratio.
  Continuum
• FREEFREE
  This routine computes the free-free continuum (bremsstrahlung) using the fitting formulae of Itoh et al. (ApJS 128, 125, 2000) and Sutherland (MNRAS 300, 321, 1998).
  
• FREEBOUND
  Calculates the free-bound (radiative recombination) continuum.
  
• TWO_PHOTON
  Calculate the 2 photon continuum from a hot, low density plasma.
  Level populations
• SHOW_POPS
  To display populations of significant levels in a CHIANTI ion model
  
• PLOT_POPULATIONS
  electron density for a specific temperature
  
• POP_PLOT
  To compute n_j A_ji / N_e for a selected transition(s) and plot it against N_e. If it is insensitive to N_e, then the line(s) is suitable for emission measure analysis.
  
• POP_PROCESSES
  Outputs to the screen the contributions of the different physical processes to the population of the specified level within the ion.
  Miscellaneous
• RAD_LOSS
  Calculates energy loss rate by free-free (ff), radiative recombination (fb) and by line (bound-bound) radiation.
  
• PLOT_IONEQ
  Plots the ionisation equilibrium values for an element. Explanation :
  
• MAX_TEMP
  Calculates temperature at max ionisation ratio for an ion Explanation :
  
• CHIANTI_DEM
  Calculates the Differential Emission Measure DEM(T) using Constant pressure or density can be used.
  
• PLOT_DEM
  To plot differential emission measure (DEM) values
  
• INTEGRAL_CALC
  To compute the atomic data integral for use in column or volume emission measure work.
  
• READ_ABUND
  to read CHIANTI abundance files
  
• READ_DEM
  to read values the differential emission measure as a function of temperature
  
• READ_IONEQ
  to read files containing the ionization equilibrium values
  
• CH_READ_FITS
  Read standard CHIANTI FITS binary table data containing the output from CH_SYNTHETIC and output a TRANSITIONS structure.
  
• CH_WRITE_FITS
  Write standard FITS binary table data from CHIANTI input structure.
  
• WHICH_LINE
  Upon given an ion name and wavelength, this routine prints out a list of possible line IDs for the wavelength. Wavelengths within 1% of the input wavelength are searched for.
  
• USE_CHIANTI
  Sets up system variables for use of CHIANTI routines Explanation : The CHIANTI software uses system variables that have to be defined. This routine is called by the CHIANTI routines if these system variables are not defined.
  

Routine Descriptions

 PROJECT

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 

 NAME

     CH_SS

 PURPOSE:
       Widget-based multi-purpose routine 
       to calculate CHIANTI line intensities and continua, to create a 
       synthetic spectrum, to make tables of lines, etc. 

 CALLING SEQUENCE:

       IDL> ch_ss


 PROCEDURE:

     This routine calculates a synthetic spectrum by merging line 
     intensities and continua. 


     The widget is organised into four Sections: 

     SECTION 1:

      -The Calculation of the  CHIANTI line intensities. 
      
       This can be  done in two ways:

       1-Restore a save file with the CHIANTI line intensities already
       calculated.   

       2-Calculate CHIANTI line intensities  with a call to CH_SYNTHETIC. 

       In this case, A series of parameters must be set:

       - Minimum and maximum wavelengths in Angstroms

       - The model used for the calculation. Three are the options:
          1) a constant  density (cm^-3) 
          2) a constant pressure (cm^-3 K) 
          3) a general (Te,Ne) model. In this case, a file will be read.
             This file should have two columns, one with the Te (K)
             values, and one with the Ne (cm^-3) values.

       - The  ionization fraction file to be used.  "*.ioneq"  files
          can be selected from  either  the CHIANTI database, the 
          working directory or selected via a widget.

       - All ions ?  If set to yes (default), then all the ions present in the
                     database will be included.
 
                     If set to no, then it is possible to select a list of ions
                     with a widget 

       - All lines ? If set to no (default), only the lines for which there are
                      observed energy levels are included 
       
                     If set to yes, also the lines that do not have
                     corresponding observed energy levels are included. In this
                     case, the wavelengths are calculated from the theoretical
                     energy levels, and might not be very accurate.
       
       - Isothermal ?  If set to no (default), a DEM file must be selected. 
                         "*.dem"  files (i.e. files with a .dem extension)
                       can be selected from either  the CHIANTI database, the 
                       working directory or selected via a widget.
       
                       If set to yes, then the user is requested to enter one
                       or more temperatures (as logarithmic values - Log T )
                       and correspondent column emission measures EM
                       logarithmic values.
                       NOTE: if more than one value is entered, then the
                             sequence must be  separated by commas (e.g.: 6.0,
                             6.5, 7.), and both Log T and Log EM must have the
                             same number of values 

       - Photoexcitation ?
                       If set to yes, you have to define:
                       Trad: The blackbody radiation field temperature
                       R/Ro: Distance from the centre of the star in stellar
                             radius units 

       Units:  Photons or Ergs'
       
       Protons: If set to Yes, the proton data are used to calculate the level population    


     Once all the parameters have been defined, the user should click on the
     "Calculate intensities" button to start the calculation (which calls 
     CH_SYNTHETIC). 

     Once the calculation is finished, an IDL  structure is loaded into
     memory. It is then possible to save it for later use by clicking  on the
     "SAVE" button. 
      The RESTORE button is to restore previously saved files into an IDL
      structure in memory.

     Once the IDL structure with the line intensities is in the memory, it is
     then possible to calculate and plot a spectrum (SECTION 2).

     SECTION 2:

              This section controls the parameters that are needed to fold the
              line intensities and the continua into a synthetic
              spectrum. These parameters are used by MAKE_CHIANTI_SPEC.

              Before this is done, a set of line intensities MUST be in the
              program memory. This is done either by calculating the
              intensities  or by restoring a save file with
              previously calculated values (SECTION 1). 

              Setting the parameters:

              -Minimum and maximum wavelengths in Angstroms

              -spectrum bin size in Angstroms. Disallowed if an Effective area
                 file is used.
              
              -instrumental FWHM: Setting this to a non-zero value broadens
                                  each of the spectral lines with a Gaussian of
                                  the specified FWHM (in Angstroms) so
                                  mimicking the effects of instrumental
                                  broadening. 
              
              -continuum: Add continua to the binned spectrum:
                          free-free, free-bound and two-photon.
                          Please note that the continuum calculation takes some
                          time and you may want to define a minimum abundance
                          value to speed the calculations.

              - All lines ? If set to no (default), only the lines for which there are
                           observed energy levels are included.
                           If set to yes, the "unobserved lines" will be added, but
                           only if they are present in the structure.


              -elemental abundances
                          "*.abund"  files (i.e. files with a .abund
                         extension) can be selected either from the CHIANTI database,
                          the  working directory, or via a widget. 

              -select a minimum abundance value
                         If set not null, only the lines of those elements
                         which have an abundance greater than the value set are
                         selected. Also, the continuum is calculated only for
                         those elements which  have an abundance greater than
                         the value set. This can significantly speed up the
                         calculations. By default, the minimum value in the
                         selected abundance file is used. To have an idea of
                         what minimum abundance should be set, the abundances
                         of Allen (1973) give: 

                         abundance (H)  = 1.
                         abundance (He) = 0.085
                         abundance (C)  = 3.3e-4
                         abundance (O)  = 6.6e-4
                         abundance (Si) = 3.3e-5
                         abundance (Fe) = 3.9e-5

              
              Eff. Area: Yes/No 

              If you want to fold the spectrum with an effective area.  
              If set to Yes, you are requested to choose an input ascii file
              with two columns, the wavelength and the effective area values
              (cm^2). 
              The wavelenghts in the file (that might not be linear)  are used
              to create the spectrum, that is multiplied with the effective
              area values.
		    Note that this option only works well if a sufficient number
		    of bins is given. The line intensities contributing to each
		    bin are summed, and  subsequently convolved with a gaussian
		    of full-width-half-maximum FWHM, if FWHM is not set = 0.
                   Please note that the convolution might not work if a small
                   number of  bins is defined. 

                Also note that to have the correct output units  (counts s-1
                bin-1) the appropiately scaled DEM (or EM) values must be provided.


              After this, by clicking on the "Calculate and plot" button the
               program calculates and plots the synthetic spectrum. 
              
              Once the spectrum is displayed, it is then possible to
              view the details of the lines by clicking with the mouse in the
              plot window, and to  perform various operations by clicking on
              the buttons in SECTION 3
              
     SECTION 3:

              This Section allows the user to select a few parameters for the
              plotting, and to create different types of OUTPUT.
              
              Labels ? : Setting this to yes plots a vertical line for each
                         spectral line in the spectrum, and also writes a label
                         above the strongest lines indicating the ion from
                         which the line arises. 
              
              Min.:      Only lines which have an intensity greater than  the
                         value set here will be listed and, if requested,
                         labelled and selected for inclusion in the various
                         outputs.  Setting the value=0.  will result in all
                         lines being listed and written in the outputs.
              
              X,Y, XOOM, UNZOOM: It si possible to select a region of the
                                 spectrum, by zooming with the use of the mouse
                                 or by setting the X,Y ranges.

                                NOTE that only the line details and portion of
                                the spectrum shown will be output.

              LINEAR/LOG  To plot the spectrum in linear or log scale
 
              Create PS file: A postscript file is created. 

              Hardcopy: the postscript file "idl.ps" is created and sent to the
                        default printer. 
              
              Save Line details (latex): The  details of the lines shown in the
                                         plot will be  saved in a latex file.
              
              Save Line details (ascii): The  details of the lines shown in the
                                         plot will be  saved in an ascii file.
              
              

              Save Spectrum (ascii): The  X,Y values of the plot are saved in
                                     an ascii file.

              Save Spectrum (IDL/FITS): The details of all the lines and the arrays
                                   of the X,Y values of the plot are saved into
                                   an IDL or FITS file. The  IDL structure 
                                   has the following tags: 

            .LAMBDA:   The array of wavelength X values

            .SPECTRUM: The array of spectrum Y values

            .UNITS       The units of LAMBDA, SPECTRUM 
            .INSTR_FWHM  The Instrumental FWHM
            .BIN_SIZE         Width of the Bins  (fixed) in angstroms
            .ABUND_NAME  The CHIANTI abundance file name
            .ABUND       The abundance values
            .MIN_ABUND   The minimum abundance value used
            .ABUND_REF   The references
            .CONTINUUM   The values of the continuum (if
                                                calculated)
            .EFFAREA       The array of effective area
                                      values (optional)
            .FILE_EFFAREA  The name of the effective area file used (optional).


            .IONEQ_NAME     The ion balance file used (full path).
            .IONEQ_LOGT        The Log10 T values associated.
            .IONEQ_REF      The references.

            .DEM_NAME       The differential emission measure file eventually  used
                            (full path).
            .DEM            The Log10 DEM values 
            .DEM_LOGT          The Log10 T values associated.
            .DEM_REF        The references.

            .MODEL_NAME    A string indicating the model used 
                     (e.g. constant density or constant pressure).

            .MODEL_NE    the Ne value.
            .MODEL_PE    the Pe value.


            .WVL_UNITS  The wavelength units.

            .WVL_LIMITS    The wavelength limits specified by the user.

            .INT_UNITS  The intensity units

            .LOGT_ISOTHERMAL
                       The Log10(T) values used. 

            .LOGEM_ISOTHERMAL
                       The Log10(EM) values used. 

            .TIME      The date and time when the structure was created.

            .VERSION   The version number of the CHIANTI database used.

            .ADD_PROTONS 
                       A flag (0/1) to indicate whether proton data were used (1)
                       or not (0) to calculate the level population.

            .PHOTOEXCITATION
                       A flag (0/1) to indicate if photoexcitation was included (1)
                       or not (0).

            .RADTEMP 
                      The blackbody radiation field temperature used (if
                      photoexcitation was included).

            .RPHOT
                   Distance from the centre of the star in stellar radius units  
                   (if photoexcitation was included).

                                       THEN, FOR EACH LINE USED TO CALCULATE THE
                                       SPECTRUM:

            .LINES     A structure containing information about the lines. 
                       Its size is the number of lines in the spectrum. The 
                       tags are:

                  .peak   The peak intensity value 

                  .iz     The atomic number of the elements (e.g., 26=Fe)

                  .ion    The ionisation stage (e.g., 13=XIII)

                  .snote  The identification of the ion (e.g., 'Fe XXIV d')

                  .ident  The identification of the transition, configuration
                           and terms in text form.

                  .ident_latex
                          The identification of the transition, configuration
                           and terms in latex form.

                  .lvl1   The lower level of the transition (see .elvlc 
                          file for ion)

                  .lvl2   The upper level for transition.

                  .tmax   The temperature of maximum emission of the line 
                          (i.e., the temperature at which the product of 
                          the emissivity and the ion fraction has its 
                          maximum). Rounded to nearest 0.1, and zero in case
                          the isothermal approximation is used. 

                  .fwhm 

                  .wvl    Wavelength of the transition, in Angstroms.

                  .flag   A flag, =-1 if the line has only theoretical energy
                          levels. Otherwise flag=0.

                  .int    Intensity of line  (with the  abundance factor multiplied)



              Save Spectrum (FITS): The entire information contained in the
                                    IDL structure is stored in a FITS file. 
                                    
     SECTION 4:
              Here, text information messages are printed. 

 INPUTS

     None.

 OPTIONAL INPUTS:
     The font 

 OUTPUTS:
     Many.
 
 KEYWORD PARAMETERS:
     
     FONT  the font to be used. Can be useful to customize the appearance of
           the widget.

 CALLS:

     CH_SYNTHETIC, CH_LINE_LIST, CH_DRAWBOX, MAKE_CHIANTI_SPEC, CH_XMENU_SEL,
     plus many other CHIANTI and SolarSoft routines.


 PROGRAMMING NOTES

     Within CH_SS, there are several other routines which are:

     OPLOT_LINES   This overplots lines and a label on the displayed 
                   spectrum.
     SYN_CURSOR    When the mouse is clicked when on the spectrum window, 
                   this routine prints out the list of nearby lines and 
                   their IDs in the text window.

     CALC_SYN_SPECTRUM
                   Calculates line intensities with a call to CH_SYNTHETIC

     PLOT_SYN_SPECTRUM  This calls make_chianti_spec to produce the 
                        intensity vs. wavelength plot.
     SYN_MAIN_EVENT  This handles the widget operations

     SYN_WID       This creates the widgets.     

 COMMON BLOCKS:
        many

 RESTRICTIONS:

 SIDE EFFECTS:

 EXAMPLE:

     IDL> ch_ss

 CATEGORY:
	
	spectral synthesis.


 WRITTEN     : 

       Ver.1, 7-Nov-01, Giulio Del Zanna (GDZ) and Peter Young (PRY)  

 MODIFICATION HISTORY:

       V.2, 7-Nov-01, GDZ . Fixed a small bug (now the spectrum plot is always
       plotted within the widget), and modified the option to add continua.
       Changed the suggested  names of the outputs. 
       Corrected a bug when creating an IDL save file with the spectrum, when
       no line details are present.

       V.3 28-Jan-02 GDZ
           fixed a bug in the density text widget, added a few buttons 
           and options, including the effective area.
            Added noprot, rphot, radtemp keywords to the call to ch_synthetic

       V 4, 18-Apr-2002, GDZ 
           Added  photoexcitation, changed IDL save files to FITS files,

       V.5, 21-May-2002, GDZ 
        fixed a few small bugs: checking min_abund before calculating the
                                spectrum; checking the ioneq file when
                                restoring the structure; changed the status of
                                all lines;  chnaged the font system.
                               generalized directory concatenation to work for 
                               Unix, Windows  and VMS.

       V.6, 15-July-2002, GDZ - New major revision.

           Changed the chianti top directory (for Effective areas).
           Changed  Linear/Log button. 

            Rearranged the sizes of the buttons and added a special cursor to
            highlight the area where  details of the lines will be given. Works
            only in linear scale.

           Added quite a lot of new checks to avoid crashes and
           fixed the problem with the zoom/unzoom/change units.

       V.7, 2-Aug-02, GDZ

           Modified the output labels on the plot, inside and on the axis.
           Also modified a few minor things like the appearance of the Log T,EM
           values. 
           Fixed a bug when creating the latex output.
           Now it restores at the end  previous colors and settings. 
 
       V.8, 8-Aug-02, GDZ
           Changed the CHIANTI system variables. Fixed.
           Also fixed a problem with the element ab. file.

      V.9, 13-Aug-02, GDZ 

           Restored the correct use of ch_line_int, now only the lines in the
           plot window are listed, and the ALL keyword is in use. 
           Now the correct xrange is loaded into COMMON when line int. are
           restored. Now it checks if all ions were in the structure, when
           restoring the line intensities, and flags the widget button accordingly.
           Added a device,decomposed=0. to remove problems with colors.
           Corrected the use of the DEM, IONEQ and ABUND pulldown menus,
           avoiding conflicts between files in the working and CHIANTI
           directory having the same name.
           Added printing of references for ancillary files, and a check on the
           element abundances vs. the elements present in the structure.

       V.10, 7-Nov-03  GDZ

          Modified format e8.2 to e9.2 for Windows compatibility.
          Replaced f9.4 with f11.4 format for the wavelengths.
          Some minor modifications to the widget.

          Added extended details in the ascii output spectrum.

          Added more explanations in the HELP buttons.

       V.11,  22-Jul-2005  GDZ 

          -Added keV option and a few more extra checks.

       V.12,  2-Aug-2005 GDZ
           put RETAIN=2 in the main plotting window.

 TO DO LIST:
           Control the range of Angstroms when clicking
           kev
           Allow plots in intensities instead of intensities A-1

 VERSION     :  V.12,  2-Aug-2005

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	CH_SYNTHETIC

 PURPOSE:

       to calculate CHIANTI line intensities or G(T) and output an IDL structure. 

 PROCEDURE:

       This routine calculates as default line intensities for a user-specified 
       differential emission measure and ionisation balance. The actual 
       creation of a synthetic spectrum (i.e., wavelength vs. intensity) 
       is performed by other routines - see CH_SS.PRO and 
       MAKE_CHIANTI_SPEC.PRO.

       Note that this routine does not include the element abundances 
       in the line intensities, as this will be performed by 
       make_chianti_spec. One of the reasons why  element abundances are not
       included in the line intensities calculation is so that it is easier 
       for the user to see how  modifying abundances affects their spectra in
       e.g. CH_SS.PRO. 

       The calculations are performed at constant pressure or 
       at constant density.

       The routine can also output line intensities calculated with an
       isothermal approximation.

	If the isothermal approximation is not used, then the user will be asked
	to select two  files, that can either be in the 
	standard CHIANTI database or in the working directory. 

       These files are: 
       
       - an ionization fraction file 
       - a differential emission measure (DEM) file.

       The routine can also output the contribution functions G(T) of the lines,
       instead of the intensities, if the keyword GOFT is used. In this case,
       only the ionization equilibrium file needs to be selected.
       The G(T), or intensity per emission measure, is calculated as:

        G=(hc/lambda_ij)*A_ji*(N_j(X^+m)/N(X^+m))*(N(X^+m)/N(X))/ N_e /(4.*!pi)

       where A_ji is the A-value of the transition;
             (N_j(X^+m)/N(X^+m)) is the population of the upper level,
             calculated by solving the statistical equilibrium equations; 
             (N(X^+m)/N(X)) is the ionization equilibrium
             N_e is the electron density.

       unless    /PHOTONS is set, in which case the  (hc/lambda_ij) factor
       is not included.  

       If not specified otherwise, with the use of the MASTERLIST or SNG_ION
       keywords,  then the standard masterlist of the ions, which has 
       all the ions in the current CHIANTI database, is used.

       PROGRAMMING NOTES

       The DEM is not assumed to be specified at 0.1 logT intervals (which 
       is how the ion fraction are specified). Thus this routine reads 
       in the DEM vs. logT information and then uses the IDL spline 
       function to tabulate the DEM over 0.1 logT intervals. The minimum 
       and maximum temperatures are those in the DEM file, rounded up to 
       the nearest 0.1. The new DEM function tabulated over 0.1 logT 
       intervals is contained in 'dem_int'.

       For some of the dielectronic files, radiative decays that were in 
       the standard .wgfa file will also be present in the dielectronic 
       version of the .wgfa file. In these cases the line intensity 
       produced from the latter file needs to be ignored and so we have a 
       check in ch_synthetic to do this. An example is the 1-7 decay in 
       the ca_19.wgfa and ca_19d.wgfa files. In the latter case, the 
       model of the ion does not include electron excitation to level 7 
       and so the model for the 1-7 decay is incorrect, hence we ignore 
       it.

 CATEGORY:

	spectral synthesis.

 CALLING SEQUENCE:

       IDL> ch_synthetic,wmin,wmax, output=output, pressure=pressure,$
            [MODEL_FILE=MODEL_FILE, err_msg=err_msg, msg=msg, $
            density=density,all=all,sngl_ion=sngl_ion, $
            photons=photons,  masterlist=masterlist, $
            save_file=save_file , verbose=verbose, $
            logt_isothermal=logt_isothermal,$
            logem_isothermal=logem_isothermal,$
            goft=goft, ioneq_name=ioneq_name, dem_name=dem_name,$
            noprot=noprot, rphot=rphot, radtemp=radtemp, progress=progress ]



 INPUTS:

	Wmin:  minimum of desired wavelength range in Angstroms
	Wmax:  maximum of desired wavelength range in Angstroms

       PRESSURE:  pressure in emitting region (Pe,  cm^-3 K). 
                  Only a single value is accepted, and the calculation is
                  performed at constant pressure.


 OPTIONAL INPUTS :

       DENSITY:   density in emitting region (Ne, cm^-3). 
                  Only a single value is accepted, and the calculation is
                  performed at constant  density, unless LOGT_ISOTHERMAL is
                  defined. In this case, DENSITY can be an array of values, but
                  has to have the same number of elements as LOGT_ISOTHERMAL.


       MODEL_FILE    Full path of the (Te,Ne) file if defined. 
                     This file should have two columns, one with the Te (K)
                     values, and one with the Ne (cm^-3) values. If these
                     values are not sorted in ascending order of Te, the
                     routine does sort them.
                     


	SNGL_ION:  specifies  a single ion (e.g. SNGL_ION='Fe_10' to include
                 only Fe X lines) or an array (e.g. SNGL_ION=['Fe_10','Fe_11']
                 to include only Fe X and Fe XI lines) of ions to be used
                 instead of the complete set of ions specified in
                 !xuvtop/masterlist/masterlist.ions 

       MASTERLIST: string of a specific masterlist file (full path). 
                   If defined as a keyword (i.e. MASTERLIST=1 or /MASTERLIST)
                   then a widget allows the user to select a  user-defined
                   masterlist file. Shortcut for SNGL_ION.   



	IONEQ_NAME:  Name of the ionization equilization name to use.  If not
		     passed, then the user is prompted for it.

       DEM_NAME:  Name of the DEM file to used.  If not passed, then the user
		   is prompted for it.

       LOGT_ISOTHERMAL
                  Array of logarithmic temperatures.
                  If defined, the emissivities are calculated with an
                  isothermal approximation. The values are sorted in ascending
                  order.

       LOGEM_ISOTHERMAL
                  Array of logarithmic emission measures.
                  If defined, the emissivities are calculated with an
                  isothermal approximation. The values are sorted in ascending
                  order. If LOGT_ISOTHERMAL is specified without 
                  LOGEM_ISOTHERMAL then the emission measures are set to 1 
                  (logem_isothermal=0).

       RADTEMP   The blackbody radiation field temperature (default 6000 K).

       RPHOT    Distance from the centre of the star in stellar radius units.
                I.e., RPHOT=1 corresponds to the star's surface. (Default is
                infinity, i.e., no photoexcitation.)


 OUTPUTS:

       OUTPUT:    The name of the structure containing the line intensities and
                  details.  
                  The tags of the  structure are:

       .lines     A structure containing information about the lines. 
                  Its size is the number of lines in the spectrum. The 
                  tags are:

                  .iz     The atomic number of the elements (e.g., 26=Fe)

                  .ion    The ionisation stage (e.g., 13=XIII)

                  .snote  The identification of the ion (e.g., 'Fe XXIV d')

                  .ident  The identification of the transition, configuration
                           and terms in text form.

                  .ident_latex
                          The identification of the transition, configuration
                           and terms in latex form.

                  .lvl1   The lower level of the transition (see .elvlc 
                          file for ion)

                  .lvl2   The upper level for transition.

                  .tmax   The temperature of maximum emission of the line.

                          If the G(T) are output, tmax is the maximum of G(T).

                          If the isothermal approximation is used  tmax=0.

                          If a DEM is used,  tmax is the maximum of the 
                          emissivity that includes the product of the ion
                          fraction and the DEM.
                          Rounded to nearest 0.1

                  .wvl    Wavelength of the transition, in Angstroms.

                  .flag   A flag, =-1 if the line has only theoretical energy
                          levels. Otherwise flag=0.

                  .int    Intensity of line (erg/cm2/s/sr or phot/cm2/s/sr), 
                          divided by the element abundance (exclusive with .goft). 

                  .goft   The G(T) of the line (optional /exclusive with .int).


       .ioneq_name     The ion balance file used (full path).
       .ioneq_logt        The Log10 T values associated.
       .ioneq_ref      The references.

       .dem_name       The differential emission measure file eventually  used
                       (full path).
       .dem            The Log10 DEM values 
       .dem_logt          The Log10 T values associated.
       .dem_ref        The references.

       .model_name    A string indicating the model used: 

                    1- Constant density
                    2- Constant pressure
                    3- Function (Te,Ne)

       .model_file    Full path of the (Te,Ne) file if defined. Null string otherwise.

       .model_ne    the Ne value(s).

                     - a scalar if 'Constant density' is selected.
                     - an array if 'Function' is selected.
                     - 0. if constant pressure is selected.

       .model_pe    the Pe value.

                     - a scalar if constant pressure is selected.
                     - 0. if 'Constant density' is selected.
                     - an array=density*temperature if 'Function' is selected.
                          
       .model_te    the Te values if 'Function' is selected. Otherwise 0.

       .wvl_units  The wavelength units.

       .wvl_limits    The wavelength limits specified by the user.

       .int_units  The intensity units.

                   1) If LOGT_ISOTHERMAL is defined, we have two cases:
                      a) LOGEM_ISOTHERMAL is not defined, and is therefore
                         assumed to be 0 (EM=1). In this case, units are
                         'photons cm+3 sr-1 s-1' or 'erg cm+3 sr-1 s-1'.
                      b)  LOGEM_ISOTHERMAL is defined. In this case, units are
                         'photons cm-2 sr-1 s-1' or 'erg cm-2 sr-1 s-1'.

                   2) If LOGT_ISOTHERMAL is not defined, we have two cases:
                      a) intensities are calculated. In this case, units are
                         'photons cm-2 sr-1 s-1' or 'erg cm-2 sr-1 s-1'.
                      b) Contribution functions G(T) are calculated. In this
                         case, units are 
                         'photons cm+3 sr-1 s-1' or 'erg cm+3 sr-1 s-1'.

       .logt_isothermal
                  The Log10(T) values used. 

       .logem_isothermal
                  The Log10(EM) values used. 

       .date      The date and time when the structure was created.

       .version   The version number of the CHIANTI database used.

       .add_protons 
                  A flag (0/1) to indicate whether proton data were used (1)
                  or not (0) to calculate the level population.

       .photoexcitation
                  A flag (0/1) to indicate if photoexcitation was included (1)
                  or not (0).

       .radtemp 
                 The blackbody radiation field temperature used (if
                 photoexcitation was included).

       .rphot
              Distance from the centre of the star in stellar radius units  
              (if photoexcitation was included).


 OPTIONAL OUTPUTS:


       SAVE_FILE: If defined, then an IDL save file is created, with the output
                  structure. 


       GOFT:      If set,  the G(T) of the lines are calculated, and put in
                  the output structure, instead  of the line intensities.
                  Units are 'photons cm+3 sr-1 s-1' or 'erg cm+3 sr-1 s-1'



 KEYWORDS:


       ALL:  if set, then all lines are included.  This means that lines for
             which  only an approximate wavelength is known, 
             denoted by a  negative wavelength value in the .wgfa file, are
             included. These are the lines for which there are no observed
             energy levels. 


       PHOTONS:   The output intensities will be in photons instead of 
                  ergs.

       VERBOSE:   If set, the routine will list each ion it is looking at, 
                  and how many lines from each ion it is including in the 
                  spectrum.

       GOFT:      If set,  the G(T) of the lines are calculated, and put in
                  the output structure, instead  of the line intensities.
                  Units are 'photons cm+3 sr-1 s-1' or 'erg cm+3 sr-1 s-1'

       NOPROT     Switch off the inclusion of proton rates in the level 
                  balance (default).

      PROGRESS    If set, a widget appears, showing the progress of the
                  calculation and allowing the user to halt the calculation.

      NO_SUM_INT  Prevents the summing of intensities over temperature. 
                  Only works in conjunction with the LOGT_ISOTHERMAL 
                  option, and is implemented in order to work the 
                  ISOTHERMAL routine. The .INT tag in OUT.LINES becomes 
                  an array with the same number of elements as 
                  LOGT_ISOTHERMAL, corresponding to the intensities at 
                  each temperature.

 CALLS:  CH_GET_FILE
          many CHIANTI standard routines,  including:
          READ_IONEQ, READ_DEM, READ_MASTERLIST, ION2SPECTROSCOPIC,
          ZION2FILENAME, READ_WGFA,READ_ELVLC,READ_SPLUPS,POP_SOLVER,
          DESCALE_UPS, CONVERT_TERMS. 
          CONVERT_TERMS uses some standard SolarSoft routines: 
          REPSTR, STR_INDEX, DATATYPE, 
          VALID_NUM, DELVARX, INFO_PROGRESS, SAVEGEN

 COMMON BLOCKS:
          wgfa, wvl,gf,a_value
          upsilon,splstr
          elvlc,l1a,term,conf,ss,ll,jj,ecm,eryd,ecmth,erydth,eref 
          elements,abund,abund_ref,ioneq,ioneq_logt,ioneq_ref
          radiative, radt, dilute
          proton, pstr
          ionrec,rec_rate,ci_rate,temp_ionrec,luprec,lupci,status

 RESTRICTIONS:

 SIDE EFFECTS:

 CATEGORY:
	spectral synthesis.
	
 EXAMPLE:

       This routine can be called in this way:

       IDL> ch_synthetic,5.,10., output=structure, pressure=1.e+15

       To make use of the output structure, use MAKE_CHIANTI_SPEC or CH_SS
       

 PREV. HIST. :
       Based on synthetic.pro, written by Ken Dere


 WRITTEN     : 
       Ver.1, 22-Jun-00, Peter Young (PRY) and Giulio Del Zanna (GDZ)

 MODIFICATION HISTORY:

       Ver.1, 22-Jun-00, Peter Young and Giulio Del Zanna

       Ver.2, 25-Jul-00, PRY
               Removed /all keyword; make_chianti_spec can be 
                used to filter out negative wavelengths.
               Added flabel tag to output in order to pick out 
                dielectronic recombination lines.

       Ver.3, 4-Oct-00, PRY
               Replaced /all keyword.
               Corrected bug when .wgfa files contain two A-values 
                for the same transition.

       Ver.4, 5-Oct-00, PRY
               Corrected bug that gave rise to lines from the same 
                transition when the dielectronic file existed.

       V.5, 11-Oct-2000, GDZ
            eliminate the abundance call; reinstate the /masterlist keyword;
            added the tag  ident_latex to have the identification in 
            late-style format; added a tag flag=-1 for the unobserved lines,
            and =0 otherwise; reinstated all wavelengths > 0. ;
            added the calculation of the G(T);
            added  a few other tags in the output, and various checks and
            comments. 
       V.6 15-Oct-2000 ,GDZ
             Replaced calls to solarsoft routines to  standard IDL ones. 
             Corrected an error in the output creation, in relation to the
             isothermal case. Added isothermal in the output. added checks to
             the wavelengths. Default output name is TRANSITIONS. changed
             const_net and added const_net_value + a few other things.

       v.7, 27-Nov-2000, GDZ. Corrected an error in the calculation of the
       G(T). 

       Version 8, 5-Dec-2000, GDZ, DAMTP. Fixed a bug when checking the 
       values in the .splups files.

       V. 9, GDZ, 10-Apr-2001, corrected another error in the G(T) calc.

       V. 10, GDZ, 30-Oct-2001 added CHIANTI Version number, changed isothermal
            to logt_isothermal and added logem_isothermal to the output.
            Removed the use of log T values, and the calculation. 
            Added err_msg, a text string with an error message.
 
       Version 11, 8-Nov-01, GDZ

            Changed the MASTERLIST keyword. Allowed double use, as a keyword 
            and as a string.

       Version 12, 18-Nov-01, Peter Young

            Added /NOPROT, RPHOT and RADTEMP keywords; changed upsilon 
            common block.

        Version 13, 29-Apr-02, GDZ

            Added no_protons, photoexcitation, rphot, radtemp 
            tags into the output  structure. 
            Revised Header. Added the PROGRESS widget.
            Added a check if the ion is present in the Ion. Frac. file.
            Added informative MSG keyword.
            Now uses  savegen.pro to save the structure.

        V. 14, 28-May-2002, GDZ: 
                  generalize directory concatenation to work for Unix, Windows
                  and VMS. 

           modified tags: 
                          limits -> wvl_limits
                          ioneq_t -> ioneq_logt
                          wvlunits -> wvl_units
                          intunits -> int_units
                          time --> date 
                          no_protons -> add_protons
                         dem_t -> dem_logt 
                const_nte -> model_name
                const_nte_value -> model_ne, model_pe, model_te
                   removed from the main STR:   .ioneq  ctemp 
                   removed from the LINES STR:  fwhm flabel

            Added model_file  input for model Ne(T). Had to considerably
            modify the routine.

         V. 15, 16-Jul-2002, Peter Young
                  Added keyword /NO_SUM_INT.

         V. 16, 22-Jul-2002, Peter Young
                  Corrected a bug related to /NO_SUM_INT; logt_isothermal 
                  can now be specified without logem_isothermal.

         V. 17, 23-July-2002, GDZ
                  Modified a few checks on the input. Also, now it prints the
                  error message whenever the program aborts

         V.18, 2-Aug-02, GDZ
                  Replaced all DBLARR and DOUBLE calls with floats.
                  Added a comment at the end of the routine when it finishes.

         V.19, 8-Aug-02, GDZ 
                  Added more error info. Changed the use of the DENSITY
                  keyword. It is possible to input an array of values if
                  LOGT_ISOTHERMAL is defined.

         V. 20, 17-Sep-02, GDZ
                  Corrected a bug: the functional (T,N) form
                  is now only accepted if DENSITY is an array with at least two
                  values.
         V. 21, 19-Sep-02, GDZ
                  Corrected the definition of the UNITS in case LOGT_ISOTHERMAL
                  is defined.

         V. 22, 19-Aug-03, Peter Young
                  when logem_isothermal is input, the derived EM is now a
                  DOUBLE array rather than FLOAT, preventing infinities when
                  logem_isothermal values are large.

         V. 23,   4-Oct-2003, GDZ
                  modified the input to POP_SOLVER, now it is dealt with an
                  input structure.

         V.24,    10-Oct-2003, K.Dere
                  added modifications from K.Dere, regarding the satellite
                  lines. 

         V 25,    3-Nov-2003, GDZ
                 Added GROUP keyword, and modified so the progress widget can
                 be stopped within IDL Windows.

         V 26,    17-Apr-2004, Enrico Landi (EL)
                  Added the recombination/ionization population processes.

         V.27,    13-Apr-2005, EL
                  Replaced the main loop to calculate individual line intensities
                  with operations among arrays, to speed the whole program in case
                  of large numbers of lines.

 VERSION     : 27,    13-Apr-2004

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	SYNTHETIC

 PURPOSE:

       calculates a synthetic spectrum


 PROCEDURE:

                 Calculations are done assuming either constant density or
                 constant pressure. See CH_SYNTHETIC for details.


 CALLING SEQUENCE:

       SYNTHETIC,Wmin, Wmax, Fwhm, Pressure= , Lambda, Spectrum ,List_wvl, List_ident
                 ,[/all, density=, /cont, min_abund=]


 INPUTS:


	Wmin:   lower limit of the wavelength/energy range of interest (Angstroms)

	Wmax:   upper limit of the wavelength/energy range of interest (Angstroms)

       Pressure:  pressure in emitting region (cm^-3 K), or 
       Density:   density in emitting region (cm^-3).

       Fwhm:  gaussian full width at half maximum of the resolution of the output 
                  spectrum, for example, to correspond to an observed spectrum


 OPTIONAL INPUTS:

	SNGL_ION:  specifies  a single ion (e.g. SNGL_ION='Fe_10' to include
                 only Fe X lines) or an array (e.g. SNGL_ION=['Fe_10','Fe_11']
                 to include only Fe X and Fe XI lines) of ions to be used
                 instead of the complete set of ions specified in
                 !xuvtop/masterlist/masterlist.ions 

       MASTERLIST: string of a specific masterlist file (full path). 
                   If defined as a keyword (i.e. MASTERLIST=1 or /MASTERLIST)
                   then a widget allows the user to select a  user-defined
                   masterlist file. Shortcut for SNGL_ION.   


       MIN_ABUND:  If set, calculates the continuum only from those elements which 
                   have an abundance greater than min_abund. 

	DEM_NAME:  Name of the DEM file to used.  If not passed, then the user
		   is prompted for it.

	ABUND_NAME:  Name of the abundance file to use.  If not passed, then
		     the user is prompted for it.

	IONEQ_NAME:  Name of the ionization equilization name to use.  If not
		     passed, then the user is prompted for it.

       RPHOT   Distance from the centre of the star in stellar radius units.
               I.e., RPHOT=1 corresponds to the star's surface. (Default is
               infinity, i.e., no photoexcitation.)

       RADTEMP The blackbody radiation field temperature (default 6000 K).
 

 OUTPUTS:

       Lambda:  wavelength array of calculated synthetic spectrum
       Spectrum:  intensity array (erg cm^-2 s^-1 str^-1 Ang^-1),
                  unless keyword photons is set then output is is
                  photons cm^-2 s^-1 str^-1 Ang^-1
       List_wvl:  a list of wavelengths for use with synthetic_plot.pro
       List_ident:  a list of line identifications for use with 
                        synthetic_plot.pro

 OPTIONAL OUTPUTS:

	
 KEYWORD PARAMETERS:

     
	ALL:  if set, then all lines are included.  This means that lines for which
             only an approximate wavelength is known (only theoretical energy
             levels are known) are included.

	SNGL_ION:  specifies  a single ion (e.g. SNGL_ION='Fe_10' to include
                 only Fe X lines) or an array (e.g. SNGL_ION=['Fe_10','Fe_11']
                 to include only Fe X and Fe XI lines) of ions to be used
                 instead of the complete set of ions specified in
                 !xuvtop/masterlist/masterlist.ions 

       MASTERLIST: string of a specific masterlist file (full path). 
                   If defined as a keyword (i.e. MASTERLIST=1 or /MASTERLIST)
                   then a widget allows the user to select a  user-defined
                   masterlist file. Shortcut for SNGL_ION.   

       CONTINUUM:   if set, then the continuum (free-free, free-bound and
                  two-photon) are  included 

       MIN_ABUND:  If set, calculates the continuum only from those elements which 
                   have an abundance greater than min_abund.  Can speed up the 
                   calculations.  For example, from Allen (1973):
                   abundance (H)  = 1.
                   abundance (He) = 0.085
                   abundance (C)  = 3.3e-4
                   abundance (O)  = 6.6e-4
                   abundance (Si) = 3.3e-5
                   abundance (Fe) = 3.9e-5



	PHOTONS:  if set, intensities are in photons cm^-2 s^-1 sr^-1 Ang^-1

	DEM_NAME:  Name of the DEM file to used.  If not passed, then the user
		   is prompted for it.

	ABUND_NAME:  Name of the abundance file to use.  If not passed, then
		     the user is prompted for it.

	IONEQ_NAME:  Name of the ionization equilization name to use.  If not
		     passed, then the user is prompted for it.

       NOPROT   If set, then proton rates are not included.

	RADTEMP	Specify background radiation temperature (default: 6000 K)

	RPHOT   Distance from the centre of the star in stellar radius units.
               I.e., RPHOT=1 corresponds to the star's surface. (Default is
               infinity, i.e., no photoexcitation.)

 CALLS:
       
       CH_SYNTHETIC, MAKE_CHIANTI_SPEC, READ_ABUND, STRPAD


 COMMON BLOCKS: None


 RESTRICTIONS:

 SIDE EFFECTS:


 EXAMPLE:

       > synthetic,100.,200.,.1, pressure=1.e+16,lambda,spectrum,list_wvl,list_ident


 CATEGORY:

	spectral synthesis.

 WRITTEN     : 

       Version 1, 8-Nov-01, Giulio Del Zanna (GDZ). 

       Rewritten as a wrapper routine using the new procedures.

       Compared to the previous SYNTHETIC, these are the main changes:

       1-Now the PRESSURE value is a keyword as the DENSITY value
       2-The keyword CONT is now renamed CONTINUUM
       3-Added keywords PHOTONS, DEM_NAME, ABUND_NAME, IONEQ_NAME
       4-MASTERLIST can now be used both as an input string or as a keyword.
       5-The description of the line details now has the spectroscopic 
         designation at the end.


 MODIFICATION HISTORY:

       Version 2, 18-Nov-01, Peter Young
           Added /noprot, rphot and radtemp keywords.

       Version 3, 11-Dec-01, Peter Young
           Changed call to ch_strpad to strpad.

       Version 4, 28-Apr-02, GDZ, changed the call to make_chianti_spec and the
       continuum keyword.

       V. 5, 22-May-2002 GDZ.  Removed const_net definitions.

       V.6, 14-Feb-2003 GDZ.
             Fixed a bug (keyword PHOTONS was not active). 
             
 VERSION     : 6, 14-Feb-2003

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 

 NAME:
	synthetic_plot

 PURPOSE:

       to plot out synthetic spectra calculated with Synthetic
       and interactively identify spectral lines


 CATEGORY:
	
	spectroscopy

 CALLING SEQUENCE:

       SYNTHETIC_PLOT,Wvl,Spectrum,List_wvl,List_ident,fwhm


 INPUTS:

       Wvl:  wavelength array from synthetic
       Spectrum:  spectrum intensity array from synthetic
       List_wvl:  string array of spectral line wavelengths
       List_ident:  string array of spectral line identifications
       Fwhm:  when the cursor is clicked, spectral lines with fwhm
              (Angstroms) of the cursor are printed out


 KEYWORDS

	xrange:  similar to IDL keyword to determine wavelength range of plot

 OUTPUTS:

       None


 PROCEDURE:

	Click the left mouse button to select a wavelength
       Click the right mouse button to exit

 EXAMPLE:

      > synthetic,100.,200.,.1,1.e+15,wvl,spectrum,list_wvl,list_ident
      > synthetic_plot,wvl,spectrum,list_wvl,list_ident,0.1
                     
      note:  it is not necessary for the two fwhm values to be the same      

 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	May 1996:     Version 2.0
       Dec. 1998:    revised by Ken Dere
       V.4,  23 Oct 2000 GDZ, added the log keyword, and changed a few things
       in the plot. 

       Ver.5, 12-Dec-2001, Peter Young
           Changed style of printing, and made method of extracting the 
           intensity from list_ident compatible with the new version of 
           isothermal.pro.

 VERSION 5   12 Dec 2001 Peter Young

 NAME

       ISOTHERMAL

 PURPOSE:
       Computes spectra from isothermal plasmas. A number of isothermal 
       plasmas can be included.
       Note that this routine has a number of unique features that 
       distinguish it from the other CHIANTI synthetic spectra routines. 
       See the Programming Notes section.

 INPUTS:

       WMIN      Minimum of desired wavelength range in Angstroms.

       WMAX      Maximum of desired wavelength range in Angstroms.

       WAVESTEP  Bin size of spectrum (in Angstroms)

       TEMP      Electron temperature (or array).

 OPTIONAL INPUTS

       PRESSURE  Electron pressure in units of cm^-3 K.

       EDENSITY  Electron density in units of cm^-3.

       EM        Emission measure. The units of EM govern the intensity 
                 units of the emission lines (i.e., column or volume 
                 emission measure units). If EM is not specified, then the 
                 emission measure is set to (N_e * N_H) where N_e is 
                 derived from the user-specified PRESSURE or EDENSITY, 
                 and N_H is derived from the routine PROTON_DENS.PRO.

       SNGL_ION  Rather than include the entire list of CHIANTI ions in 
                 the calculation, this input can be used to select a 
                 single ion, or a number of different ions. E.g., 
                 SNGL_ION='s_2' or SNGL_ION=['s_2','s_3','s_4'].

       RADTEMP   The blackbody radiation field temperature (default 6000 K).

       RPHOT    Distance from the centre of the star in stellar radius units.
                I.e., RPHOT=1 corresponds to the star's surface. (Default is
                infinity, i.e., no photoexcitation.)

       MASTERLIST  The list of ions that will be considered for the 
                   spectrum is contained in the masterlist file in the 
                   CHIANTI directories. The user can specify his own file 
                   through this keyword. E.g., 
                   masterlist='/user/home/masterlist.ions'


	ABUND_NAME:  Name of the abundance file to use.  If not passed, then
		     the user is prompted for it.

	IONEQ_NAME:  Name of the ionization equilization name to use.  If not
		     passed, then the user is prompted for it.


  KEYWORDS

       NOPROT     Switch off the inclusion of proton rates in the level 
                  balance.

       ERGS       The units of the output spectrum are by default in photons. 
                  Setting /ERGS switches to erg units.

       CONT       Adds continuum (free-free, free-bound, two-photon) to 
                  spectrum.

  OUTPUTS:

        LAMBDA   Wavelength array of calculated synthetic spectrum.

        SPECTRUM Intensity array. The units depend on the user inputs to 
                 ISOTHERMAL -- see note below. 

        LIST_WVL A list of wavelengths for use with synthetic_plot.pro

        LIST_IDENT A list of line identifications for use with 
                   synthetic_plot.pro

 PROGRAMMING NOTES

        Intensity Units
        ---------------
        The units are of the form photons cm^3 s^-1 sr^-1 * (units of EM), 
        changing to ergs if the /ergs keyword is set.

        The volume emission measure (N_e*N_H*V) has units cm^-3.

        The column emission measure (N_e*N_H*h) has units cm^-5.


        Unique features
        ---------------
        The emission lines in the final spectrum have no width and thus 
        each occupies a single pixel of the spectrum. The size of the 
        pixels are set by WAVESTEP.

        As stated above, the units of the output spectrum are 
        photons cm^3 s^-1 sr^-1, i.e., there is no "per angstrom" term. 
        This means that (i) the height of the emission lines in the 
        spectrum does not change with varying WAVESTEP, and (ii) the height
        of continuum does change with WAVESTEP.

 COMMON BLOCKS

        ELEMENTS

 CALLS

        CH_SYNTHETIC, READ_ABUND, CH_GET_FILE, CONCAT_DIR, FREEFREE, 
        FREEBOUND, TWO_PHOTON

 HISTORY
        Ver.1, 8-Apr-02, Peter Young  Rutherford Appleton Laboratory,
        p.r.young@rl.ac.uk 
        Tries to replicate the behaviour of the original ISOTHERMAL which 
        was found in earlier versions of CHIANTI (v.3 and earlier). 

 MODIFICATION HISTORY

       Ver. 2, Giulio Del Zanna (GDZ), 28-Apr-02 
               Added abund_name,ioneq_name keywords.
               Also, added photons keyword in call to MAKE_CHIANTI_SPEC.

       Ver. 3, Peter Young, 24-May-02
                 Modified to produce arrays of spectra when an array of 
                 temperatures is given

       V.4, GDZ, 28-May-02 
              Added a couple of checks on file existence and modified the call
              to ch_synthetic and make_chianti_spec  due to change of keyword
              names.  

       V.5, Peter Young, 16-Jul-02
              Restructured routine to avoid crashes when a large number of 
              temperatures is input.

       V.6, 8-Aug-02 GDZ
              Added one error checking

       V.7, 18-Aug-03, Peter Young
              Added EM= keyword.


 VERSION     : 
       Version 6, 8-Aug-02 
        

 PROJECT     :  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 

                   
 NAME        : MAKE_CHIANTI_SPEC
     		          
 PURPOSE     : 
              To create a CHIANTI synthetic spectrum 
               
 CALLING SEQUENCE:

       IDL> make_chianti_spec, TRANSITIONS,  LAMBDA, SPECTRUM,$ 
                    [BIN_SIZE= ,  ,INSTR_FWHM= , PIXEL=PIXEL, BINSIZE = BINSIZE, $
                    WRANGE= , ALL=ALL, continuum=continuum, $
                    ABUND_NAME= , MIN_ABUND=, photons=photons, effarea=effarea


 PROCEDURE : 
 		
     From information contained in the structure TRANSITIONS, constructs 
     a synthetic spectrum

     By default, routine assumes thermal widths for lines.

   PROGRAMMING NOTES

     The line profile is constructed using the IDL gaussint routine. 
     For a wavelength pixel centred at l and with width dl, gaussint 
     is used to integrate the Gaussian up to l-dl/2 and up to l+dl/2. 
     The difference between the two is the intensity in this pixel.


    
 INPUTS      : 
		
               TRANSITIONS, the structure created by ch_synthetic.pro.
               
 OPT. INPUTS : 

     LAMBDA   Array of wavelengths (X-values). If not defined as input, it is
              calculated on the basis of BIN_SIZE, and returned as an output. 
              If defined as input, the routine checks that there are at least
              10 points in the wavelength range defined by WRANGE. If there
              are, the corresponding subset of LAMBDA is returned, otherwise
              the routine exits with an error.

     BIN_SIZE      Bin size  in Angstroms of the spectrum to be created. A linear
              spectrum is assumed. In case an effective area file is used, the
              wavelenghts in the file (that might not be linear) are used to
              create the spectrum, and this bin size looses any meaning.

     WRANGE   Allows a subset of the wavelength range to be turned into 
              a spectrum. When using syn_plot, this speeds up the routine 
              a lot if you've elected to zoom in on a region.

     INSTR_FWHM Instrumental FWHM (Angstroms). 
                In case an effective area file is used, The line intensities
                contributing to each bin are summed, and subsequently convolved
                with a gaussian of full-width-half-maximum FWHM if FWHM is not
                set = 0 . Please make sure that the FWHM value (if not set to
                zero) is larger than  the bin size. 

     ABUND_NAME  A CHIANTI abundance file name can be set. 
                It allows the abundance file given in transitions.abund_name
                (if present)   to be over-ridden. Note that it also used for
                the continuum calculation.

     MIN_ABUND: If set, calculates line intensities only from those elements
                  which  have an abundance greater than min_abund. 
                  Can speed up the calculations. For example, from Allen
                  (1973):

                   abundance (H)  = 1.
                   abundance (He) = 0.085
                   abundance (C)  = 3.3e-4
                   abundance (O)  = 6.6e-4
                   abundance (Si) = 3.3e-5
                   abundance (Fe) = 3.9e-5

     FILE_EFFAREA
                   The Effective Area File (TWO COLUMNS - wavelengths in
                   Angstroms and cm^2 values) If defined, then the spectrum is
                   multiplied with these values.  Any input  LAMBDA value is
                   over-written by the wavelenghts in the file (that might not
                   be linear) and  are used to create the spectrum.
		    Note that this option only works well if a sufficient number
		    of bins is given. The line intensities contributing to each
		    bin are summed, and  subsequently convolved with a gaussian
		    of full-width-half-maximum FWHM, if FWHM is not set = 0.
                   Please note that the convolution might not work if a small
                   number of  bins is defined. 

               
 OUTPUTS     : 
		
		LAMBDA  Array of wavelengths (X-values).
              If not defined as input, it is
              calculated on the basis of BIN_SIZE, and returned as an output. 
              If defined as input, the routine checks that there are at least
              10 points in the wavelength range defined by WRANGE. If there
              are, the corresponding subset of LAMBDA is returned, otherwise
              the routine exits with an error.


               SPECTRUM  A structure containing all the information:

                     LAMBDA      The array of X-values
                     SPECTRUM    The array of Y-values
                     UNITS       The units of LAMBDA, SPECTRUM
                     INSTR_FWHM  The Instrumental FWHM
                     BIN_SIZE    Width of the Bins  (fixed) in angstroms
                     ABUND_NAME  The CHIANTI abundance file name             
                     ABUND       The abundance values
                     MIN_ABUND   The minimum abundance value used                 
                     ABUND_REF   The references
                     CONTINUUM   The values of the continuum (if calculated)
                     
                     FILE_EFFAREA The Effective Area File used (optional)
                     EFFAREA       The array of effective area values
                                 (optional - same size of LAMBDA)

                    .LINES      An array of structures, for all the lines used               
                                to calculate the SPECTRUM. 
                                The tags are the same as those created by 
                                CH_SYNTHETIC, plus
                       .PEAK    The peak intensity of the line in the spectrum
                                (approx. value) 
	
 OPT. OUTPUTS:
		
     BINSIZE  If BIN_SIZE  is not  specified, then the spectrum 
              bin-sizes are computed automatically, and the size of the 
              bin returned in BINSIZE.


 KEYWORDS    : 

     PIXEL    The spectrum is given in /pixel units rather /ang
        (DISABLED)
      
     ALL      Add  lines that originally had negative wavelengths  
               
     PHOTONS  If set=1, the output intensities will be in photons instead of 
                  ergs.

     CONTINUUM
              If set, then the  continuum is added to the 
              spectrum.

     verbose 

 CALLS       : 
		
		PRY:     	GET_ATOMIC_WEIGHTS
		Chianti: FREEBOUND, FREEFREE
		
 COMMON       (with freefree freebound and two_photon):
 		
		elements,abund,abund_ref,ioneq,ioneq_logt,ioneq_ref

 RESTRICTIONS: The input structure has to be of the type created by ch_synthetic.
               The LAMBDA, EFFAREA values must be ordered in wavelength and the
               LAMBDA values must be in Angstroms.
               
 SIDE EFFECTS: None known yet.
               

 EXAMPLES    : 
		
		make_chianti_spec, output_struct,  LAMBDA, SPECTRUM,$
		 bin_size=0.01, instr=0.1 

 CATEGORY    : 
               spectral synthesis.

 PREV. HIST. :

      
 WRITTEN     : 
           Peter Young , CfA, pyoung@cfa.harvard.edu  1-Sept-2000

 MODIFICATION HISTORY:  
 
               Version 1, PRY 1-Sept-2000

               Version 2, Giulio Del Zanna (GDZ)  10-Oct-2000

               put ALL keyword, removed the FWHM obsolete and
               confusing call. Reorganised various minor things.

               Version 3, PRY 19-Oct-2000
                 Corrected the way continuum is treated for an isothermal 
                 spectrum.

               V. 4, 2-Nov-2001 GDZ. Now MIN_ABUND is effective not only in the
               continuum calculation but also in the line spectrum.
               Modified for the use of logt_isothermal

               V.5, GDZ, added EFFAREA keyword: an ascii file with lambdas and
                                              effective areas can be read
                                              in. The line intensities are
                                              calculated in a different way.
                        Also, changed the output.

               V.6, GDZ, 28-Apr-02 redefined completely the OUTPUT structure. 
                    Major revision (added two_photon verbose).

               V.7, GDZ, 3-May-2002
                    fixed  a bug, when negative angpix values occur.
                     
               V.8, GDZ, 22 May 2002,  changed some tags of the output, and
                    added min_abund in the continuum call.

               V.9, GDZ, 30-May-02 replaced fix() with round() 

               V. 10, 15-July-2002 , GDZ 
                    changed the location of Effective area files.

               V.11 14-Aug-02, GDZ 
                    speeded up the routine, by changing the way the PEAK tag is
                    added to the structure. The drawback is that only the
                    'standard v.4 tags' are allowed, and future additions will
                    have to be dealt properly.
  
               v.12 2-Dec-2002, GDZ. 
                   Fixed a bug:  Removed the plotting of the window with the effective areas.

               v.13 26-Apr-2005, Enrico Landi (EL)
                   Fixed a minor bug: if the lines were more than 32768 (2^15), the main
                                loop crashed.

               v.14 22-Jul-2005 GDZ 
                 -fixed a bug. When the routine was run once without
                 defining the lambdas, and then with the lambdas
                 defined (the units were switched to photons)
                 -fixed a bug. When the effective areas were used,
                 all lines were used to create the spectrum.
                 -added hard-wired switch to photons when using
                 effective area files.

                 -added the keV option

                 -now can output a spectrum only with the continuum
                 (i.e. even if no emission lines are present). 

               15, 2-Aug-2005, GDZ 
                 Added a check on the input structure. If it was
                 calculated with ch_synthetic and the keyword
                 /no_sum_int, it cannot be used here.

 VERSION     :  15, 2-Aug-2005

 STILL TO DO: 

              -speed up the routine with the use of arrays.
              -add the option to select only a list of ions, also in the
               continuum procedures.
              -Allow the use of user-defined line profiles.
              -Enable PIXEL keyword

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	ASCII_WVL_DEM

 PURPOSE:

	create an ascii file of predicted spectral line intensities and
       wavelengths corresponding to a selected abundance and differential
       emission measure (DEM).  


 PROCEDURE:

                 Calculations are done assuming either constant density or
                 constant pressure. See CH_SYNTHETIC for details.


 CALLING SEQUENCE:

       ASCII_WVL_DEM, Wmin, Wmax, Pressure= , [density= ], $ 
              [outfile= , mini= , sngl_ion=, /photons, /all, /masterlist], $
              [/noprot, radtemp=, rphot=]


 INPUTS:

	Wmin:   lower limit of the wavelength range of interest (Angstroms)	
               if kev keyword set, then wmin is in kev	
	Wmax:   upper limit of the wavelength range of interest (Angstroms)
               if kev keyword set, then wmax is in kev	

       Pressure:  pressure in emitting region (cm^-3 K), or 
       Density:   density in emitting region (cm^-3).


 OPTIONAL INPUTS:

       OUTFILE: the name of the output ascii file to be written.
	
	MINI:	Minimum intensity for a line to be included in the output.

	SNGL_ION:  specifies  a single ion (e.g. SNGL_ION='Fe_10' to include
                 only Fe X lines) or an array (e.g. SNGL_ION=['Fe_10','Fe_11']
                 to include only Fe X and Fe XI lines) of ions to be used
                 instead of the complete set of ions specified in
                 !xuvtop/masterlist/masterlist.ions 

       MASTERLIST: string of a specific masterlist file (full path). 
                   If defined as a keyword (i.e. MASTERLIST=1 or /MASTERLIST)
                   then a widget allows the user to select a  user-defined
                   masterlist file. Shortcut for SNGL_ION.   


 OUTPUTS:

	an ascii file:   linelist.txt  in the working directory by default

 OPTIONAL OUTPUTS:


 KEYWORD PARAMETERS:

	MINI:	Minimum intensity for a line to be included in the output

	SNGL_ION:  specifies  a single ion (e.g. SNGL_ION='Fe_10' to include
                 only Fe X lines) or an array (e.g. SNGL_ION=['Fe_10','Fe_11']
                 to include only Fe X and Fe XI lines) of ions to be used
                 instead of the complete set of ions specified in
                 !xuvtop/masterlist/masterlist.ions 

       MASTERLIST: string of a specific masterlist file (full path). 
                   If defined as a keyword (i.e. MASTERLIST=1 or /MASTERLIST)
                   then a widget allows the user to select a  user-defined
                   masterlist file. Shortcut for SNGL_ION.   


       PHOTONS:  units will be in photons rather than ergs

       KEV:  wavelengths will be given in kev rather than Angstroms

       ALL:  if set, then all lines are included.  This means that lines 
             for which
             only an approximate wavelength is known (only theoretical energy
             levels are known) are included.


       OUTFILE:  the name of the output ascii file to be written. By 
                default a
                file 'linelist.txt' in the user's working  directory will be
                created. 

       NOPROT  If set, then the default setting will be NOT to use 
               proton rates. This can be changed within the routine.

	RADTEMP	Specify background radiation temperature (default: 6000 K)

	RPHOT   Distance from the centre of the star in stellar radius units.
               I.e., RPHOT=1 corresponds to the star's surface. (Default is
               infinity, i.e., no photoexcitation.)

 CALLS:
       
       CH_SYNTHETIC, CH_LINE_LIST


 COMMON BLOCKS: None

 RESTRICTIONS:

 SIDE EFFECTS:


 EXAMPLE:

            IDL> ascii_wvl_dem,400.,800., out='linelist',$ 
               pressure=1.e+15,mini=1.,sngl_ion='o_4'

 CATEGORY:

	spectral synthesis.

 WRITTEN     : 

       Version 1, 8-Nov-01, Giulio Del Zanna (GDZ). 

       Compared to the previous ASCII_WVL_DEM, these are the main changes:

       1-Rewritten as a wrapper routine using the new procedures.
       2-Now the PRESSURE value is a keyword.
       3-The calculations can be done at constant DENSITY.
       4-Energies (keV) can be output instead of wavelengths in Angstroms    
       5-MASTERLIST can now be used both as an input string or as a keyword.

 MODIFICATION HISTORY:

      18-Nov-01, Peter Young
         Added /noprot, rphot and radtemp keywords
       V. 2, 22-May-2002 GDZ.  Removed const_net definitions.

 VERSION     : 2, 22-May-2002

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	LATEX_WVL_DEM

 PURPOSE:

	create a latex file of predicted spectral line intensities and
       wavelengths corresponding to a selected abundance and differential
       emission measure (DEM)


 PROCEDURE:

                 Calculations are done assuming either constant density or
                 constant pressure. See CH_SYNTHETIC for details.


 CALLING SEQUENCE:

       LATEX_WVL_DEM, Wmin, Wmax, Pressure= , [density= ], $ 
              [outfile= , mini= , sngl_ion=, /photons, /all, /masterlist]


 INPUTS:

	Wmin:   lower limit of the wavelength/energy range of interest (Angstroms)
               if kev keyword set, then wmin is in kev	

	Wmax:   upper limit of the wavelength/energy range of interest (Angstroms)
               if kev keyword set, then wmax is in kev	

       Pressure:  pressure in emitting region (cm^-3 K), or 
       Density:   density in emitting region (cm^-3).


 OPTIONAL INPUTS:


       OUTFILE: the name of the output latex file to be written.
	
	MINI:	Minimum intensity for a line to be included in the output.

	SNGL_ION:  specifies  a single ion (e.g. SNGL_ION='Fe_10' to include
                 only Fe X lines) or an array (e.g. SNGL_ION=['Fe_10','Fe_11']
                 to include only Fe X and Fe XI lines) of ions to be used
                 instead of the complete set of ions specified in
                 !xuvtop/masterlist/masterlist.ions 

       MASTERLIST: string of a specific masterlist file (full path). 
                   If defined as a keyword (i.e. MASTERLIST=1 or /MASTERLIST)
                   then a widget allows the user to select a  user-defined
                   masterlist file. Shortcut for SNGL_ION.   

       RPHOT   Distance from the centre of the star in stellar radius units.
               I.e., RPHOT=1 corresponds to the star's surface. (Default is
               infinity, i.e., no photoexcitation.)

       RADTEMP The blackbody radiation field temperature (default 6000 K).
 

 OUTPUTS:

	a latex file:   'linelist.tex'  in the working directory by default


 OPTIONAL OUTPUTS:

	
 KEYWORD PARAMETERS:

	MINI:	Minimum intensity for a line to be included in the output

	SNGL_ION:  specifies  a single ion (e.g. SNGL_ION='Fe_10' to include
                 only Fe X lines) or an array (e.g. SNGL_ION=['Fe_10','Fe_11']
                 to include only Fe X and Fe XI lines) of ions to be used
                 instead of the complete set of ions specified in
                 !xuvtop/masterlist/masterlist.ions 

       MASTERLIST: string of a specific masterlist file (full path). 
                   If defined as a keyword (i.e. MASTERLIST=1 or /MASTERLIST)
                   then a widget allows the user to select a  user-defined
                   masterlist file. Shortcut for SNGL_ION.   


       PHOTONS:  units will be in photons rather than ergs

       KEV:  wavelengths will be given in kev rather than Angstroms

       ALL:  if set, then all lines are included.  This means that lines for which
             only an approximate wavelength is known (only theoretical energy
             levels are known) are included.


       OUTFILE:  the name of the output latex file to be written. By default a
                file 'linelist.tex' in the user's working  directory will be
                created. 

       NOPROT   If set, then proton rates are not included.


 CALLS:
       
       CH_SYNTHETIC, CH_LINE_LIST


 COMMON BLOCKS: None

 RESTRICTIONS:

 SIDE EFFECTS:


 EXAMPLE:

             > latex_wvl_dem, 400.,800., mini=1, pressure=1.e+15,sngl_ion='o_4'


 CATEGORY:

	spectral synthesis.

 WRITTEN     : 

       Version 1, 8-Nov-01, Giulio Del Zanna (GDZ). 

       Compared to the previous LATEX_WVL_DEM, these are the main changes:

       1-Rewritten as a wrapper routine using the new procedures.
       2-Now the PRESSURE value is a keyword.
       3-The calculations can be done at constant DENSITY.
       4-MASTERLIST can now be used both as an input string or as a keyword.


 MODIFICATION HISTORY:

       Version 2, 18-Nov-01, Peter Young
           Added /noprot, rphot and radtemp keywords.

       V. 3, 22-May-2002 GDZ.  Removed const_net definitions.
             
 VERSION     : Version 3, 22-May-2002

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 



 NAME:
	CH_LINE_LIST

 PURPOSE:

	Create a latex or an ascii file of predicted spectral line intensities and
       wavelengths corresponding to  selected parameters, as calculated by 
       CH_SYNTHETIC. Needs as input the line intensity structure calculated by
       CH_SYNTHETIC (default)  or the SPECTRUM structure output of
       MAKE_CHIANTI_SPEC.

 CALLING SEQUENCE:

       IDL> ch_line_list, transitions, outname, latex=latex, ascii=ascii, $
       abundfile=abundfile, min_abund=min_abund, $
       wmin=wmin,wmax=wmax,$
       SPECTRUM=SPECTRUM, minI=minI,photons=photons,kev=kev, $
       all=all,no_sort=no_sort, sngl_ion=sngl_ion


 PROCEDURE:


 INPUTS:

       The structure created by CH_SYNTHETIC

 OPTIONAL INPUTS:

	Wmin:   lower limit of the wavelength/energy range of interest (Angstroms)
               if kev keyword set, then wmin is in kev	
	Wmax:   upper limit of the wavelength/energy range of interest (Angstroms)
               if kev keyword set, then wmax is in kev	

       Mini:   Minimum intensity for line to be included in output
	
	SNGL_ION:  specifies a single ion (or a list of ions) to be used instead
                 of the complete set of ions specified in the structure.


       MIN_ABUND:  If set, outputs  only  those elements which 
                   have an abundance greater than min_abund.  

                   For example, from Allen (1973):
                   abundance (H)  = 1.
                   abundance (He) = 0.085
                   abundance (C)  = 3.3e-4
                   abundance (O)  = 6.6e-4
                   abundance (Si) = 3.3e-5
                   abundance (Fe) = 3.9e-5


 KEYWORD PARAMETERS:

       LATEX:  Create a latex file (default, exclusive with /ASCII)

       ASCII:  Create an ascii file (exclusive with /LATEX)

	MINI:	Minimum intensity for line to be included in output

       PHOTONS:  units will be in photons rather than ergs

       KEV:  wavelengths will be given in kev rather than Angstroms

       ALL:  if set, then all lines are included.  This means that lines for which
             only an approximate wavelength is known, denoted by a negative 
             wavelength value in the .wgfa file, are included.
             These lines are listed in the file with a * preceding the wavelength.

       NO_SORT:
             If set, then the lines are *not* sorted in wavelength (or energy).

       SPECTRUM

             If set, IT IS ASSUMED that the input structure is the SPECTRUM
             structure output of MAKE_CHIANTI_SPEC, where the  line
             intensities have already been multiplied by the abundance factor!!


 OUTPUTS:

	A latex (default) or an ascii file with the line list

 CALLS: Many SolarSoft routines.


 COMMON BLOCKS:
        none.

 SIDE EFFECTS:


 EXAMPLE:

             > ch_line_list, trans,'linelist.tex',/latex, wmin=100.,wmax=200.,/all


 CATEGORY:

	spectral synthesis.


 WRITTEN     : 
       Version 1, Written by: Giulio Del Zanna (GDZ) Oct 31 2001.

 MODIFICATION HISTORY:

        V.2, 9-Nov-2001 GDZ. 
                 Now correctly handles the case when no
                 abundances are passed to the routine. 

        v.3, 11-Dec-2001, PRY.
                 Removed calls to get_utc and anytim2cal. Replaced with 
                 call to systime()
 
        v.4, 29-Apr-02, GDZ

                 Fixed a few small bugs, some caused by a change in the
                 database file format for V4. 
                 Added only_mini,  file_effarea keywords to be able to use as
                 input the structure created by MAKE_CHIANTI_SPEC.

        V.5, 22-May-2002, GDZ
                 generalized directory concatenation to work for
                 Unix, Windows  and VMS. changed tags.
                 Changed and added various things, including flabel

        V.6, 12-Aug-02, GDZ
           Modified the output labeling, and fixed two bugs: 1) when /all was used
           the keyword /mini was not working. 2) min_abund was not working
           properly when /spectrum was used.  Reduced size of latex output (was
           12pt)
           Changed output in isothermal case (no Tmax given). Better info printed (GDZ)

        V.7, 3-Nov-03  GDZ
           Modified format e8.2 to e9.2 for Windows compatibility.

        v.8, 18-Jul-2005 GDZ
           Modified the use of the /kev keyword. Also, now the
           routine accepts input structure with the units in keV. 

        v.9, 4-Aug-2005 GDZ
           Corrected a bug introduced in the previous version.
           Also switched to \documentclass when making the latex file.


 VERSION     : 9, 4-Aug-2005

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 

 NAME: EMISS_CALC()
       
 PURPOSE:

       To compute the emissivities of all lines of a specified ion over
	given ranges of temperature and density.

 CATEGORY:

       Scientific analysis

 EXPLANATION:

 	This routine calculates:

		hc
       	--  * N_j  * A_ji
      	       lamb

 	where hc = 1.986 * 10^-8 erg AA, lamb is in angstroms, N_j is the 
	fraction of ions in the upper emitting level j, and A_ji is the 
	radiative decay rate for the transition.

	The emissivities are stored in a structure called EMISS that also
	holds the wavelength of the transition, the level numbers i and j 
	and also a 'flag', which is set to -1 if the wavelength is negative.

	The temperature and density ranges can be specified directly using
	the TEMP and DENS keywords. Setting TMAX to the log T_max of the 
	ion, gives emissivities for 3 temperatures: log T_max +- 0.15. 
	If DENS is not set, then it is set to 8 to 12 in 0.5 dex intervals. 
	STDENS allows the start density (of 8) to be changed to some other 
	value; ND allows the number of densities to be varied (default 9); 
	DINT allows the density interval to be varied (default 0.5).

 CALLING SEQUENCE:

       EMISS=EMISS_CALC (IZ, ION, [ TEMP=TEMP, DENS=DENS, RADT=RADT, $
				DIL=DIL, PATH=PATH, /NO_DE, /PROTON, $
				QUIET, PRESSURE=PRESSURE)

 EXAMPLES:

	EMISS=EMISS_CALC(26,13)
	EMISS=EMISS_CALC(26,13,temp=[6.2],dens=findgen(5)+8)
	EMISS=EMISS_CALC(26,13,temp=findgen(11)/100.+5.5,press=10.^15)

 INPUTS:

	IZ	The atomic number of the ion

	ION	The spectroscopic number of the ion (e.g., 12 = XII)

 OPTIONAL INPUTS:

	TEMP	Direct specification of the temperature range (log T)

	DENS	Direct specification of the density range (log Ne)

	RADTEMP	Specify background radiation temperature (default: 6000 K)

	RPHOT   Distance from the centre of the star in stellar radius units.
               I.e., RPHOT=1 corresponds to the star's surface. (Default is
               infinity, i.e., no photoexcitation.)

	PATH	If specified, the routine will look for the atomic data in 
		the PATH directory, rather than in the CHIANTI database

	PRESSURE	If a temperature array is given, and PRESSURE set, 
			then the emissivities will be evaluated at the 
			specified temperatures, but for densities = 
			pressure/temperature. If DENS is set, then it will 
			be ignored. The pressure is assumed to be in units 
			K * cm^-3.

       ABUND_FILE  The name of a CHIANTI abundance file. This is used for 
               calculating the proton to electron ratio. Default is 
               !abund_file.

       IONEQ_FILE  The name of a CHIANTI ion balance file. This is used for 
               calculating the proton to electron ratio and evaluating 
               the T_max of the ion. Default is !ioneq_file.

       SUM_MWL_COEFFS  An array of coefficients of the same length as 
                       the array of temperatures. Electron and proton rate 
                       coefficients will be calculated at each temperature 
                       and then a weighted sum of the coefficients is 
                       performed using SUM_MWL_COEFFS. This allows 
                       non-Maxwellian energy distributions to be 
                       incorporated into the level balance equations.
                       This keyword is not compatible with the PRESSURE
                       keyword.

       RADFUNC         The name of a user-defined function that will generate
                       a radiation spectrum as a function of temperature. 
                       This radiation field will replace the black-body that
                       is assumed when using the RADTEMP keyword in the call
                       to pop_solver.

 KEYWORDS:

	NO_DE	Drops the hc/lambda factor in the computation of the 
		emissivities. Useful for emission measure analyses involving 
		photon fluxes

       NOPROT  If set, then the default setting will be NOT to use 
               proton rates. This can be changed within the routine.

	QUIET	If set, don't list the temperatures and densities at which 
		the emissivities are caculated.

       DIEL   If the dielectronic recombination files exist for the ion, 
               then these are used to derive the emissivities.

       NO_SETUP  If emiss_calc is called from a routine where the ELEMENTS
                 common block has already been set up, then this keyword
                 stops emiss_calc loading up the common block

 OUTPUT:

	The structure that is output has the following tags:

	.ion_name	string; contains ion name, e.g., 'Fe XIII'
	.lambda		float; contains wavelength
	.level1		integer; contains lower level of transition
       .lvl1_desc      string; gives config. and term of lower level
	.level2		integer; contains upper level of transition
       .lvl2_desc      string; gives config. and term of upper level
	.flag		integer; a flag to mark particular transitions
	.em		fltarr(nt,nd); contains emissivities at particular 
			  temperatures and densities.

 PROGRAMMING NOTES:

	Transitions where only theoretical energies are available for at 
	least one of the two levels are assigned negative wavelengths in 
	the .wgfa file. With emiss_calc, the wavelength is set to be 
	positive, but emiss.flag is set to -1 for that transition, so 
	that other routines can keep track of the theoretical wavelengths.

 COMMON BLOCKS:

	ELVLC, WGFA, UPSILON, RADIATIVE, PROTON, ELEMENTS, IONREC

 CALLS:

	SETUP_ION, POP_SOLVER
       ZION2FILENAME, ZION2SPECTROSCOPIC
	READ_PROT, PROTON_DENS

 HISTORY:

	Ver 1, PRY 28-Jun-97
	Ver 2, PRY 26-Jul-97  - corrected problem with size of emiss
	Ver 3, PRY 22-Sep-97  - allowed photo-excitation to be included
	Ver 4, PRY 6-Jul-98   - added PATH
	Ver 5, PRY 5-Sep-98   - added call to choose_ioneq
       Ver 6, PRY 3-Dec-98   - dosen't crash if no params given
	Ver 7, PRY 9-Jan-99   - allowed proton rates to be added through 
				/PROTON keyword.
	Ver 8, PRY 10-Feb-99  - added /QUIET keyword
	Ver 9, PRY 8-Oct-99   - for H-like ions, there's a 2-photon 
				transition with a non-zero A-value that is 
				assigned a zero wavelength (as it does not 
				produce an emission line). This caused 
				problems for dens_plotter, so emiss_calc 
				now removes this transition from the emiss 
				structure.
	Ver 10, PRY 15-Dec-99 -	added deu to the upsilon common block in 
				order to be consistent with the main Chianti 
				routines.
	Ver 11, PRY 8-May-00  - added PRESSURE
       Ver 12, PRY 17-Aug-00 - changed elvlc common block to match new 
                               version of pop_solver
       Ver 13, PRY 10-Oct-00 - now calls setup_ion to read ion data
       Ver 14, PRY 1-Jun-00  - removed call to choose_ioneq; now makes use 
                               of the !ioneq_file system variable.
       Ver 15, PRY 25-Sep-01 - modified for 9-point splines and proton rates
       Ver 16, PRY 9-Dec-01  - completed changes for v.4

       V. 17, 29-May-2002, Giulio Del Zanna (GDZ) 
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 
                   Now we only call zion2filename, corrected the call to
                   zion2spectroscopic (dielectronic cases were not handled
                   correctly).

       V.18, 6-Aug-2002, Peter Young
                   Theoretical wavelengths weren't being flagged so this 
                   has now been corrected.

       V.19, 7-Aug-2002, Peter Young
                   Stopped "lines" with zero wavelength being included in 
                   the structure.
                   Changed the use of CHIANTI system variables.

       V.20 14-Aug-2002, GDZ 
                   Modified the use of Version, to make it compatible with the
                   other CHIANTI v.4 routines.

       V.21 10-Sep-2002, Peter Young
                   Allowed a density of 1 cm-3 to be input.

       V.22 7-Aug-2003, Peter Young
                   Added keyword /NO_SETUP

       V.23  4-Oct-2003, GDZ
                  modified the input to POP_SOLVER, now it is dealt with an
                  input structure.

       V.24  5-Mar-2004, Enrico Landi (EL)
                  included ionization and recombination as level population
                  processes

       V.25  6-May-2005, EL
                  corrected a minor incompatibility with IDL 5.6

       V.26  5-Jul-2005, Peter Young
                  added RADFUNC= and SUM_MWL_COEFFS= keywords

       V.27  1-Aug-2005, Peter Young
                  re-ordered code for setup to prevent crash

       V.28  3-Aug-2005,GDZ
                  fixed bug, only define ioneq_ionrec when files are
                  there (it was failing with neutrals)


 VERSION     :   28  3-Aug-2005

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	GOFNT

 PURPOSE:

	calculate G(n,T) function (line intensity per unit emission measure)
       
 PROCEDURE:

	Must specify line to form numerator and denominator
       Multiple lines can be selected and summed
       This can now be done interactively or not.

 CALLING SEQUENCE: 

	GOFNT,Ion,Wmin,Wmax,Temperature,G,Desc,density=


 INPUTS:

       Ion:   the CHIANTI style name of the ion, i.e., 'c_5' for C V

       Wmin:  minimum of wavelength wavelength range of interest in Angstroms

       Wmax:  maximum of wavelength wavelength range of interest

 OPTIONAL INPUTS:

       Many - see the keywords below.

 OUTPUTS:

	Temperature:  an array of temperatures 

       G:  Intensity  per unit emission measure N_e*N_H*dh [cm^-5].
           The resulting units are therefore erg cm^+3 s^-1 sr-1

           C(T)= 1/(4*!pi)* A_ji*(N_j(X^+m)/N(X^+m))*(N(X^+m)/N(X))*(N(X)/N(H))/N_e

            unless  /NOABUND is set, in which case 
           C(T)= 1/(4*!pi)* A_ji*(N_j(X^+m)/N(X^+m))*(N(X^+m)/N(X))/N_e

           G(T)=(hc/lambda_ij)*C(T) 
           G(T)= C(T)   if /PHOTONS is set

       Desc:  a short string description of the selected line


 OPTIONAL OUTPUTS:

	Postscript file withthe plot of G(T).

       Ascii file with the values of G(T). 
        
       VALUE      The array of G(T) values corresponding to logt0.


 KEYWORD PARAMETERS:


	PRESSURE:  specifies the pressure in units of NeT (cm^-3 K).  G is then
                  calculated at that constant pressure 
		
	DENSITY:  specifies the electron density in units of cm^-3.  G is then 
                 calculated at that value of the electron density.  If neither the 
                 density or pressure keywords are specified, a constant
                  density of 1.e+10 cm^-3 is assumed

       PHOTONS:  sets output in photons/s

       RPHOT   Distance from the centre of the star in stellar radius units.
               I.e., RPHOT=1 corresponds to the star's surface. (Default is
               infinity, i.e., no photoexcitation.)

       RADTEMP The blackbody radiation field temperature (default 6000 K).

       OUTFILE:  the (optional) name of the output ascii file where a 
                   listing of the line ratio intensity as a function of 
                   temperature is saved.

       PSFILE:  the (optional) name of the output postscript file 
                  where a plot of the chosen G(T) is saved.

       NOABUND: If set, the G(T)'s are not multiplied by the abundance 
                factor.

       NOPROT   If set, then proton rates are not included.


	ABUND_NAME:  Name of the abundance file to use.  If not passed, then
		     the user is prompted for it.

	IONEQ_NAME:  Name of the ionization equilization name to use.  If not
		     passed, then the user is prompted for it.

       ALL          If set, all lines are calculated, including
                    the 'unobserved' ones. 

       LOWER_LEVELS
       UPPER_LEVELS
                    Arrays with the indices of the lower and upper levels
                    pertaining to the transitions you want to get. 
                    If more than one couple is given, the G(T) of the 
                    lines are summed.
                    Obviously, the given indices must correspond to transitions
                    that are present in the database.

       ARCSECS  
                 If set, units are photons (ergs) cm^+3 s^-1 arcsecs^-2

       VERBOSE

       LOGT0       An array of log T values for which the G(T) are wanted.
       VALUE       The array of G(T) values corresponding to logt0.
 
                   If logt0 is defined, and within the limits of the 
                   temperatures for which G(T) NE 0, the array VALUE
                   is returned with a simple spline interpolation.

 CALLS:

       CH_SYNTHETIC, CH_XMENU_SEL

 COMMON BLOCKS: None

 RESTRICTIONS:

 SIDE EFFECTS:

 EXAMPLE:

      IDL> gofnt,'o_5',1000.,1500.,temp,goft,desc,density=1.e+16


 CATEGORY:

	spectral diagnostics


 MODIFICATION HISTORY:

 	Written by:	Ken Dere
	October 4, 1996:     Version 1
       14-Jul-2000     Peter Young, now calls pop_solver

       26-Oct-2000 GDZ, added keyword NOABUND to not multiply for the abundence
       factor. Corrected header for a wrong description.

	Version 4, 21-Dec-2000, William Thompson, GSFC
		Modified for better cross-platform graphics capability

  
       Version 5, 8-Nov-01, Giulio Del Zanna (GDZ). 

       Rewritten as a wrapper routine using the new procedures.
           Corrected a few inconsistencies in the plots.

       Version 6, 18-Nov-01, Peter Young
           Added /noprot, rphot and radtemp keywords.

       Version 7, 11-Dec-01, Peter Young
           Changed call to ch_strpad to strpad.

       V. 8, GDZ, 28-Apr-02 Added abund_name,ioneq_name keywords.
       v. 9  21-May-2002, GDZ
             generalized directory concatenation to work for
             Unix, Windows  and VMS. 

       V.10, 15-Aug-02, GDZ 
              Major revision:
              -Removed the call to ch_xselect_s, that did not work for long lists.
              -Added a '*' in the line lists, to identify 'unobserved' lines.
              -Replaced the commands to create PS file, to make it
               cross-platform compatible.
              -Added a large number of cosmetics, mainly lables to the axes and
               titles.
              -Added keyword ALL. If set, all lines are calculated, including
              the 'unobserved' ones. 
              -Added the CHIANTI version number in the outputs.

       V. 11, 19-Sep-02, GDZ
              Clarified output units.

       V.12, 25-Jun-03, GDZ, 
              Added many new keywords. Now is possible to use the routine 
              with background jobs, in not-interactive mode.
              Rounded the wavelengths. 

       V.13, 24-Sept-2003, GDZ 
              Corrected a bug when logt0 is not defined.

       V.14, 3-Nov-03  GDZ
             Modified format e8.2 to e9.2 for Windows compatibility.

 VERSION     :   14, 3-Nov-03 

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME: G_OF_T()
       
 PURPOSE:

	To compute DE * F(T) * n_j * A_ji / N_e for selected emission lines. 
	Option to also multiply by abundance.

 CATEGORY:

       Atomic data analysis

 EXPLANATION:

	The G-of-T function has a number of different definitions in the 
	literature. In the most basic form it contains only the temperature 
	dependent parts (i.e., 0.83*n_j*A_ji*F(T)/N_e), but often a Delta-E 
	and Ab(X) are added as well. Here, the _default_ form is:

	Delta-E * 0.83 * n_j * A_ji * F(T) / N_e

	By using the NO_DE keyword, the Delta-E can be omitted, while the 
	ABUND keyword allows the abundance to be added.

	The function that is output is tabulated over 4.0 <= logT <= 8.0 
	in 0.1 dex intervals. If you want the function tabulated over 
	smaller intervals, run the ION_INTERP routine afterwards.

 CALLING SEQUENCE:


 EXAMPLES:

	RESULT=G_OF_T(26,13)

	RESULT=G_OF_T(26,13,DENS=7)

	RESULT=G_OF_T(26,13,GOFTFILE='my_gofts.dat')

       RESULT=G_OF_T(26,13,/ABUND)

       RESULT=G_OF_T(26,13,ABUND_FILE=ABUND_FILE, IONEQ_FILE=IONEQ_FILE)

 INPUTS:

	IZ:	The atomic number of the ion (e.g., 26 = Fe)

	ION:	The spectroscopic number of the ion (e.g., 12 = XII)

 OPTIONAL INPUTS:

	DENS:	The logarithm (to base 10) of the density at which the 
		emissivities are calculated (default=10.)

	WRANGE: Wavelength range from which lines are required. If not 
		specified, then the 10 strongest lines are displayed.

	PATH:	If specified, the routine will look for the atomic data in 
		the PATH directory, rather than in the CHIANTI database

	GOFTFILE:	By specifying GOFTFILE as a filename, the G-of-T 
			function can be stored in this file. It is stored 
		in the form a structure (called goft_list) with the following 
		labels:

	  goft_list.label: user-specified string, e.g., 'Si XII  520.7'
	  goft_list.func:	 fltarr(41), the G-of-T function

	If the same GOFTFILE is specified for another ion, then the 
	G-of-T function is added to the existing structure. The GOFTFILE 
	option only works when the ABUND keyword is set. The GOFTFILE is 
	meant to be read by another routine called GOFT_PLOTTER.

	INDEX:	Allows the direct specification of indices within the 
		emiss structure. This allows the g_of_t routine to be 
		run without the menu widget appearing. If the /quiet 
		keyword is also used, then the routine will run "silently".

	RADTEMP	Specify background radiation temperature (default: 6000 K)

	RPHOT   Distance from the centre of the star in stellar radius units.
               I.e., RPHOT=1 corresponds to the star's surface. (Default is
               infinity, i.e., no photoexcitation.)

       IONEQ_FILE  Directly specify the name of the ion balance file 
               (including directory path). If not set, then a widget will 
               pop up allowing you to select a file.

       ABUND_FILE  Directly specify the name of the abundance file 
               (including directory path). One can also use /ABUND_FILE 
               to include the abundances in the G(T) function, but allow 
               the abundance file to be picked through a widget.

 KEYWORDS:

       NOPROT  If set, then the default setting will be NOT to use 
               proton rates. This can be changed within the routine.

	NO_DE:	If set, then the output function will *not* contain the 
		Delta-E. Be careful using this if you are using blends 
		(as Delta-E is different for different wavelengths).

	QUIET	If set, then don't plot the G(T) function or print out 
               information to the screen.

 CALLS:

	EMISS_CALC, READ_IONEQ, READ_ABUND, EMISS_SELECT, CH_GET_FILE

 RESTRICTIONS:


 HISTORY:

	Ver.1, PRY 28-Jul-97.
	Ver.2, PRY 22-Jun-98, added CHOOSE keyword and removed RAY
	Ver.3, PRY 4-Aug-98, cosmetic changes following comments of Giulio 
			Del Zanna
	Ver.4, PRY 5-Sep-98, added call to choose_ioneq
	Ver.5, PRY 23-Sep-98, added GOFTFILE input
	Ver.6, PRY 3-Mar-99, now calls EMISS_SELECT
       Ver.7, PRY 6-Nov-00, removed the /CHOOSE keyword; also changed 
                       PICKFILE call to DIALOG_PICKFILE and removed call 
                       to the CHIANTI routine ADD\_SUBDIR
       Ver.8, PRY 18-Oct-01, adjusted for proton rates, and 
                       photoexcitation.
       Ver.9, PRY 9-Dec-01, completed modifications for v.4 of CHIANTI.

       V.  10, 21-May-2002, Giulio Del Zanna (GDZ) 
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS.
       Ver. 11, 9-Feb-2005, Peter Young
                   changed keyword_set(abund) to keyword_set(abund_file)

 VERSION     :   11, 9-Feb-2005

 PROJECT

       CHIANTI   http://wwwsolar.nrl.navy.mil/chianti.html

       CHIANTI is an atomic database package for the calculation of
       continuum and emission line spectra from astrophysical plasmas. It is a 
       collaborative project involving the Naval Research Laboratory
       (Washington DC, USA), the Arcetri Observatory (Firenze, Italy), and the
       Cambridge University (United Kingdom).

 NAME
        dens_plotter

 PURPOSE:
        A widget-based routine to allow the analysis of density sensitive
        ratios. **** See RATIO_PLOTTER for details. *****

 CALLING SEQUENCE:

       IDL>  dens_plotter,  name,$ 
                  EM, PATH=PATH, NOPROT=NOPROT, $
                  IONEQ_FILE=IONEQ_FILE, ABUND_FILE=ABUND_FILE


 INPUTS:
        The ion name (e.g. 'si_3' for Si III)

 OPTIONAL INPUTS : none

 OUTPUTS:

 OPTIONAL OUTPUTS:

	EM:	Save the displayed emissivities to structure EM.
               **** See RATIO_PLOTTER for details. *****

 KEYWORDS:


	PATH:	Data in the CHIANTI format that is not in the CHIANTI 
		database can be read by specifying the directory in which 
		it lies through PATH.

       ABUND_FILE  The name of a CHIANTI abundance file. This is used for 
               calculating the proton to electron ratio. Default is 
               !abund_file.

       IONEQ_FILE  The name of a CHIANTI ion balance file. This is used for 
               calculating the proton to electron ratio and evaluating 
               the T_max of the ion. Default is !ioneq_file.

       NOPROT  If set, then the default setting will be NOT to use 
               proton rates. This can be changed within the routine.


 CALLS:   CONVERTNAME RATIO_PLOTTER
      

 COMMON BLOCKS: none


 RESTRICTIONS:

 SIDE EFFECTS:

 CATEGORY:
	spectral synthesis.
	
 EXAMPLE:
             IDL> dens_plotter, 'si_9'


 WRITTEN     : 
              Ver.1, 18-Apr-2002, Giulio Del Zanna (GDZ) written as a wrapper
              routine to call RATIO_PLOTTER.

             
 MODIFIED:   V.2,  2-Aug-2005, GDZ
              Now the routine handles the dielectronic case


 VERSION     :   2,  2-Aug-2005

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	DENSITY_RATIOS

 PURPOSE:

	to calculate line intensity ratios as a function of electron density

 CATEGORY:

	scientific analysis

 CALLING SEQUENCE:

       DENSITY_RATIOS,Ion,Wmin,Wmax,Dmin,Dmax,Density,Ratio,Description


 INPUTS:

       Ion:   the CHIANTI style name of the ion, i.e., 'c_5' for C V
	wmin:  minimum of the wavelength range of interest in Angstroms
	wmax:  maximum of the wavelength range of interest in Angstroms
       dmin:  log10 of the minimum desired density (8. = 10^8 cm^(-3) )
       dmax:  log10 of the maximum desired density range

 INTERACTIVE INPUTS:

	Must select the line for the numerator and denominator 
       It is possible to select multiple lines to be summed
	
 KEYWORD PARAMETERS:

        OUTFILE:  the (optional) name of the output ascii file where a 
                   listing of the line ratio intensity as a function of 
                   density is saved.  For example, outfile='den_rat.lis'

        PSFILE:  the (optional) name of the output postscript file 
                  where a plot of the choses density sensitive line
                  ratio is saved.  For example, psfile='den_rat.ps'

        TEMP:   to specify the temperature, otherwise the temperature at 
                  the peak 
                  of the ionization equilibrium is used.  For example, 
                  temp=1.e+6

        /PHOTONS:  if set, the ratio will be in photon units, as opposed 
                   to ergs    

	RADTEMP	Specify background radiation temperature (default: 6000 K)

	RPHOT   Distance from the centre of the star in stellar radius units.
               I.e., RPHOT=1 corresponds to the star's surface. (Default is
               infinity, i.e., no photoexcitation.)

       NOPROT  If set, then the default setting will be NOT to use 
               proton rates. This can be changed within the routine.

       VERBOSE To print out information about the lines.

 OUTPUTS:

	Density:  an array of the density values for which the selected 
                   intensity ratio calculated 
       Ratio:    an array of line intensity ratios
       Description:  a string describing the transitions selected

       Plots the intensity ratio of the selected line as a function of density


 COMMON BLOCKS:

       None.

 CALLS

       EMISS_CALC, ION2SPECTROSCOPIC, CONVERTNAME, READ_IONEQ,
       CH_XMENU_SEL

 EXAMPLE:

       density_ratios,'o_5',1000.,1500.,8.,13.,den,rat,desc 

       choose the ratio of 1371.294 to 1218.393 

 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	March 1996:     Version 2.0
       May 28, 1996:  Ken Dere added psfile keyword/option
       Sept 1996:     modified to work with VMS
                      and added keyword TEMP, Ken Dere
       Feb. 2000:     Modified for Version 3, K. Dere
       14-Jul-2000    Peter Young, now calls pop_solver
       26-Sep-2001    Modified for 9-point splines and proton rates; 
                      added radtemp and rphot keywords for photoexcitation.
       20-Nov-2001    Routine now calls emiss_calc to get emissivities.

       V.9, 21-May-2002, Giulio Del Zanna (GDZ) 
                      generalized directory concatenation to work for
                               Unix, Windows  and VMS.
       V.10, 1-Aug-02 GDZ
          Changed all the formats.

       V.11, 06-Aug-02 GDZ
              Changed the use of CHIANTI system variables. 

       V.12, 15-Aug-02, GDZ 
              Major revision:
              -Added the keyword VERBOSE, to avoid printing out long lists of lines.
              -Removed the call to ch_xselect_s, that did not work for long lists.
              -Added a '*' in the line lists, to identify 'unobserved' lines.
              -Replaced the commands to create PS file, to make it
               cross-platform compatible.
              -Added a large number of cosmetics, mainly lables to the axes and
               titles, that were missing.
              -Removed plotting in windows already present.
              -Added the CHIANTI version number in the outputs.

        V.13, 3-Nov-03  GDZ
           Modified format e8.2 to e9.2 for Windows compatibility.

 VERSION     :   13, 3-Nov-03

 Project     : SOHO - CDS     
                   
 Name        : CHIANTI_NE
               
 Purpose     : Calculate and plot CHIANTI density sensitive line ratios.
               
 Explanation : CHIANTI_NE (density ratios)
               calculates and plots density sensitive line ratios based on 
               the CHIANTI atomic database of Dere et. al.
               
 Use         : IDL> chianti_ne
    
 Inputs      : None
               
 Opt. Inputs : None
               
 Outputs     : None
               
 Opt. Outputs: None.
               
 Keywords    : None

 Calls       : CALC_DMM_DR, plot_dmm_dr_fig , make_ion_list

 Common      : dmm_dr_com  dmm_lines(with plot_dmm_dr_fig), 
               
 Restrictions: None
               
 Side effects: None
               
 Category    : Spectral
               
 Prev. Hist. : Started life as 'density_ratios' by Ken Dere

 Written     : C D Pike, RAL, 13-Jan-96
               
 Modified    : Added selection of els/ions from master file.  CDP, 21-Jan-96
               Added hardcopy of line list, refs etc.          CDP, 22-Jan-96
               Include multiple lines in ratio.                 CDP, 27-Jan-96
               General upgrade and added temp/unit selections.   CDP,  6-Jun-97
               Added intensity ratio selection.                 CDP, 17-Jul-97
               Added wavelength ranges.                        CDP, 18-Jul-97
               Fixed typos introduced in version 7.           CDP, 22-Jul-97
               Float the user-supplied Log Temperature.      CDP, 1-Aug-97
               Update for IDL v5.2.                         CDP, 20-Apr-99
               v. 11 Update list of elements.                    CDP, 18-Jun-99

               V.12. Added ratio plots and hardcopies in linear scale, added various
               checks and  minor things. Added a few tags to the 
               ratio output structure (temperature, units, comment). 
               Removed optional output structure. 
               Updated to be CHIANTI v.3-compatible.
               Giulio Del Zanna, DAMTP, 7-Oct-2000 
		Version 13, 21-Dec-2000, William Thompson, GSFC
			Modified for better cross-platform graphics capability

               V. 14, 1-May-02, GDZ, commented out a few refs.
               V. 15,  21-May-2002, GDZ, changed the way to deal with fonts.
               V.16, 17-Sep-2002 (GDZ) 
                    added !p.multi = 0 upon exit and added X-label.


 Version     : Version 16, 17-Sep-2002 

 Project     : SOHO - CDS     
                   
 Name        : PLOT_CHIANTI_NE
               
 Purpose     : Plots a density sensitive ration saved from CHIANTI_NE
               
 Explanation : The routine CHIANTI_NE allows the calculated ratio to be
               saved in an IDL save file.  This routine retrieves and
               plots the ratio.
               
 Use         : IDL> plot_chianti_ne, file, data
    
 Inputs      : file - save file name (an extension of .CH_NE will have
                                      been added, specifying this is optional)
               
 Opt. Inputs : None
               
 Outputs     : None
               
 Opt. Outputs: data - returns the retrieved ratio structure
               
 Keywords    : log. If set, a log-log plot is produced.

 Calls       : print2d_plot 

 Common      : None
               
 Restrictions: None
               
 Side effects: None
               
 Category    : Synthetic spectra
               
 Prev. Hist. : None

 Written     : C D Pike, RAL, 7-Oct-96
               
 Modified    : v.2 Added a few extra things, including possibility to create a
               postscript file. 
               Giulio Del Zanna (DAMTP), 10-Oct-2000

 Version     : Version 2, GDZ 10-Oct-2000 

 PROJECT

       CHIANTI   http://wwwsolar.nrl.navy.mil/chianti.html

       CHIANTI is an atomic database package for the calculation of
       continuum and emission line spectra from astrophysical plasmas. It is a 
       collaborative project involving the Naval Research Laboratory
       (Washington DC, USA), the Arcetri Observatory (Firenze, Italy), and the
       Cambridge University (United Kingdom).

 NAME
        temp_plotter

 PURPOSE:
        A widget-based routine to allow the analysis of temperature sensitive
        ratios. **** See RATIO_PLOTTER for details. *****

 CALLING SEQUENCE:

       IDL>  temp_plotter,  name,$ 
                  EM, PATH=PATH, NOPROT=NOPROT, $
                  IONEQ_FILE=IONEQ_FILE, ABUND_FILE=ABUND_FILE


 INPUTS:
        The ion name (e.g. 'si_3' for Si III)

 OPTIONAL INPUTS : none

 OUTPUTS:

 OPTIONAL OUTPUTS:

	EM:	Save the displayed emissivities to structure EM.
               **** See RATIO_PLOTTER for details. *****

 KEYWORDS:


	PATH:	Data in the CHIANTI format that is not in the CHIANTI 
		database can be read by specifying the directory in which 
		it lies through PATH.

       ABUND_FILE  The name of a CHIANTI abundance file. This is used for 
               calculating the proton to electron ratio. Default is 
               !abund_file.

       IONEQ_FILE  The name of a CHIANTI ion balance file. This is used for 
               calculating the proton to electron ratio and evaluating 
               the T_max of the ion. Default is !ioneq_file.

       NOPROT  If set, then the default setting will be NOT to use 
               proton rates. This can be changed within the routine.


 CALLS:   CONVERTNAME RATIO_PLOTTER
      

 COMMON BLOCKS: none


 RESTRICTIONS:

 SIDE EFFECTS:

 CATEGORY:
	spectral synthesis.
	
 EXAMPLE:
             IDL> temp_plotter, 'fe_13'

 WRITTEN     : 
              Ver.1, 18-Apr-2002, Giulio Del Zanna (GDZ) written as a wrapper
              routine to call RATIO_PLOTTER (written by P. Young).

 MODIFIED:   V.2,  2-Aug-2005, GDZ
              Now the routine handles the dielectronic case


 VERSION     :   2,  2-Aug-2005

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	TEMPERATURE_RATIOS

 PURPOSE:

	calculate and display temperature sensitivity of line intensity ratios

 CATEGORY:

	spectral diagnostics

 PROCEDURE :

       The intensities (Population of the upper level * A)  of the lines within
       the selected ion are first  calculated, either at constant pressure or
       at constant density (however specified in the input). They are plotted
       in window 0. The intensities  relative to the brightest  reference line
       are then plotted in window 1. A widget allows the user to select a
       number of lines (at least one!) for the numerator of the ratio, and a
       number of lines for the denominator. In case of multiple selections, the
       line intensities are summed. The ratio values are plotted in window 2, and
       optionally also saved in a text file. A postscript file can also be
       created. The ratio values, calculated at twice and half the prescribed
       density  are also calculated and overplotted, to show how the
       temperature ratio also depends on the density.

 CALLING SEQUENCE:


      > temperature_ratios,ion,wmin,wmax,Log10(tempmin),Log10(tempmax),temperature,ratio,description,$
       [pressure= ,density= , psfile= , outfile= ]


 EXAMPLE:

      > temperature_ratios,'c_4',100.,1600.,4.,6.,temp,ratio,desc,density=1.e+10,$ 
        psfile='test.ps', outfile='test.txt'

       then select  the  ratio of (384.17 + 384.19) to 1550.772



 INPUTS:

       Ion:   the CHIANTI style name of the ion, i.e., 'c_5' for C V

       Wmin:  minimum  wavelength  limit in Angstroms

       Wmax:  maximum  wavelength  limit in Angstroms

       Tempmin:  log10 of lowest temperature of interest, i.e. 4 for 10.^4 K

       Tempmax:  log10 of highest temperature of interest

 OPTIONAL INPUTS:

	Must specify indices of lines which are to form the ratio
	
       RADTEMP   The blackbody radiation field temperature (default 
                 6000 K).

       RPHOT     Distance from the centre of the star in stellar radius 
                 units. I.e., RPHOT=1 corresponds to the star's surface. 
                 (Default is infinity, i.e., no photoexcitation.)

       ABUND_FILE  The name of a CHIANTI abundance file. This is used for 
                 calculating the proton to electron ratio. Default is 
                 !abund_file.

       IONEQ_FILE  The name of a CHIANTI ion balance file. This is used for 
                 calculating the proton to electron ratio and evaluating 
                 the T_max of the ion. Default is !ioneq_file.

 OUTPUTS:

	Temperature:  an array of temperatures spanning Tempmin to Tempmax

       Ratio:  an array of the intensity ratio of the selected lines

       Desc:  a short string description of the selected line ratio


 OPTIONAL OUTPUTS:

	Ps and/or  text file with the  intensity ratio.


 KEYWORD PARAMETERS:

		
	DENSITY:  calculates the intensity ratios for constant density.

                  If neither density or pressure are specified, a constant
                  density of 1.e+10 cm^-3 is assumed as default.

       OUTFILE:  the (optional) name of the output ascii file where a 
                   listing of the line ratio intensities as a function of 
                   temperature is saved.

       PSFILE:  the (optional) name of the output postscript file 
                  where a plot of the chosen temperature sensitive line
                  ratio is saved.

       NOPROT    Switches off inclusion of proton rates.

       VERBOSE   prints out information

 CALLS: 

        read_ioneq, convertname, ion2spectroscopic,ion2filename,
        ch_xmenu_sel, emiss_calc

 COMMON:

       elvlc,l1a,term,conf,ss,ll,jj,ecm,eryd,ecmth,erydth,eref
       wgfa, wvl,gf,a_value
       upsilon,t_type,deu,c_ups,splups
       proton, pstr, pe_ratio
       radiative, radt, dilute

 RESTRICTIONS:

               
 SIDE EFFECTS: None known yet.
                 

 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	May 1996:     Version 2.0, Ken Dere
       April 2000:   V. 3 Ken Dere modified for V3
       14-Jul-2000   V. 4  Peter Young, now calls pop_solver
        2-Oct-2000   V. 5 Giulio Del Zanna, corrected an error in the 
             creation of the string list of the lines in the ratio. 
             Also corrected a few minor errors.
             Removed the device,window_state call, and added a few 
             other 'cosmetic' adjustments.  
	Version 6, 21-Dec-2000, William Thompson
	      Modified for better cross-platform capability.

       Ver.7, 6-Dec-2001, Peter Young
             Revised to call emiss_calc for the emissivities.

       V.8, 21-May-2002, GDZ 
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

       V.9, 1-Aug-02 GDZ
          Fixed label mistake, and changed all the formats.

       V.10, 06-Aug-02 GDZ
              Changed the use of CHIANTI system variables. 

       V.11, 15-Aug-02, GDZ 
              Major revision:
              -Added the keyword VERBOSE, to avoid printing out long lists of lines.
              -Removed the call to ch_xselect_s, that did not work for long lists.
              -Added a '*' in the line lists, to identify 'unobserved' lines.
              -Replaced the commands to create PS file, to make it
               cross-platform compatible.
              -Added a large number of cosmetics, mainly lables to the axes and
               titles, that were missing.
              -Removed plotting in windows already present.
              -Removed the pressure keyword.
              -Added the CHIANTI version number in the outputs.

        V.12, 3-Nov-03  GDZ
           Modified format e8.2 to e9.2 for Windows compatibility.

 VERSION     :   12, 3-Nov-03

 Project     : SOHO - CDS     
                   
 Name        : CHIANTI_TE
               
 Purpose     : Calculate and plot CHIANTI temperature sensitive line ratios.
               
 Explanation : CHIANTI_TE (temperature ratios)
               calculates and plots temp. sensitive line ratios based on 
               the CHIANTI atomic database of Dere et. al. 
               
 Use         : IDL> chianti_te 
    
 Inputs      : None
               
 Opt. Inputs : None
               
 Outputs     : None
               
 Opt. Outputs: none. 
               
 Keywords    : None

 Calls       : CALC_DMM_TR, make_ion_list

 Common      : dmm_tr_com
               
 Restrictions: None
               
 Side effects: None
               
 Category    : Spectral
               
 Prev. Hist. : Started life as 'temperature_ratios' by Ken Dere

 Written     : H.E. Mason, 3 Oct 1996 

 Modified    : Update for IDL v5.2.  CDP, 20-Apr-99
               V.3.  Update list of elements.  CDP, 18-Jun-99

               V.4 , Giulio Del Zanna (DAMTP), 10 Oct-2000
               Rewritten completely, adding possibility to select the density
               at which the intensities are calculated,  making this routine
               compatible ith CHIANTI v.3, and with the same characteristics as
               CHIANTI_TE. Added ratio plots and hardcopies in linear scale, added various
               checks and  minor things. Added a few tags to the 
               ratio output structure (density, units, comment). 
               Removed optional output structure.
		Version 5, 21-Dec-2000, William Thompson, GSFC
			Modified for better cross-platform graphics capability

               V. 6, 1-May-02, GDZ, commented out a few refs.
               V.7,  21-May-2002, GDZ, fixed a bug with the fonts.
               V.8, 17-Sep-2002 (GDZ) 
                    added !p.multi = 0 upon exit and added X-label

 Version     : Version 8, 17-Sep-2002

 Project     : SOHO - CDS     
                   
 Name        : PLOT_CHIANTI_TE
               
 Purpose     : Plots a temperature sensitive ratio saved from CHIANTI_TE
               
 Explanation : The routine CHIANTI_TE allows the calculated ratio to be
               saved in an IDL save file.  This routine retrieves and
               plots the ratio.
               
 Use         : IDL> plot_chianti_te, file, data
    
 Inputs      : file - save file name (an extension of .CH_TE will have
                                      been added, specifying this is optional)
               
 Opt. Inputs : None
               
 Outputs     : None
               
 Opt. Outputs: data - returns the retrieved ratio structure
               
 Keywords    : log. If set, a log-log plot is produced.

 Calls       : None

 Common      : None
               
 Restrictions: None
               
 Side effects: None
               
 Category    : Synthetic spectra
               
 Prev. Hist. : None

 Written     : C D Pike, RAL, 7-Oct-96
               
 Modified    : v.2 Added a few extra things,  including possibility to create a
               postscript file. 
               Giulio Del Zanna (DAMTP), 10-Oct-2000

 Version     : Version 2, GDZ 10-Oct-2000 

 PROJECT     :  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 

 NAME

     FREEFREE

  PURPOSE:

     This routine computes the free-free continuum (bremsstrahlung) 
     using the fitting formulae of Itoh et al. (ApJS 128, 125, 2000) 
     and Sutherland (MNRAS 300, 321, 1998).

     The Itoh et al. data are valid for smaller ranges for temperature 
     and wavelength than Sutherland and so for points outside of their 
     ranges we use the data of Sutherland.

 INPUTS

    TEMP    Temperature (in K).

    WVL     Wavelengths in angstroms. Can be a scalar or vector.

 OUTPUTS

    INT     Free-free continuum intensity in units of 
            10^-40 erg cm^3/s/sr/Angstrom  
            [ integral(N_H N_e dh) in cm^-5 ] if a DEM is not defined. 

            If DEM values are defined, it is assumed that they are given
            as N_H N_e dh/dT.  The units are 10^-40 erg/cm^2/s/sr/Angstrom. 

            If T is given as a 1-D array, then the output will be a 2-D array,
            with one element for each temperature and wavelength 
            (but also see SUMT).

 OPTIONAL INPUTS

    DEM_INT An array of same length as TEMP which contains the 
            differential emission measure values at each temperature. 
            The emissivity at each temperature is multiplied by the 
            DEM value and the d(logT) value.

    MIN_ABUND This keyword allows the specification of a minimum abundance, 
              such that any elements with an abundance (relative to 
              hydrogen) less than MIN_ABUND will not be included in the 
              calculation. E.g., MIN_ABUND=1e-5.

 KEYWORDS

    NO_SETUP By default the routine asks the user which ion balance 
             and abundance files to use via pop-up widgets. If 
             /no_setup is used then this data is taken from the common 
             block.

    SUMT     The default is to output the intensity array as an array 
             of size (nwvl x nT). Setting this keyword performs a sum 
             over the temperatures to yield a vector of same size as 
             the input wavelengths, thus producing the complete 
             free-free spectrum.

    PHOTONS  Gives output emissivity in photon units rather than ergs.

 CALLS

    SUTHERLAND, ITOH

 COMMON BLOCKS

    ELEMENTS

 PROGRAMMING NOTES

    The Itoh fitting formula is only valid for (6.0 LE logT LE 8.5). 
    For temperatures below this, we thus switch to the Sutherland 
    fitting formula. There is very little (<1%) between the two at 
    logT=6.

    Itoh also has a constraint on the quantity u=hc/kTl (l=wavelength), 
    such that (-4 LE log u LE 1.0). The upper limit corresponds to the 
    continuum being cut-off prematurely at low wavelengths. E.g., for 
    T=10^6 the cutoff is at 14.39 angstroms. For these low wavelengths 
    we also use the Sutherland data to complete the continuum. Note that 
    the continuum at these wavelengths is very weak

 MODIFICATION HISTORY

    Ver.1, 5-Dec-2001, Peter Young
         Completely revised to call the separate itoh.pro and 
         sutherland.pro routines.

    V. 2, 21-May-2002,  Giulio Del Zanna (GDZ),
          Corrected the description of the  units.
          Added verbose keyword and a printout.

    V. 3, 22-May-2002,  Peter Young (PRY)
          Added MIN_ABUND optional input.
          Changed ioneq_t to ioneq_logt (GDZ).

       V 4, 25-May-2005, GDZ 
                  corrected routine header.

 VERSION     :  4, 25-May-2005

 PROJECT:  CHIANTI

      CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
      Astrophysical Plasmas. It is a collaborative project involving the Naval
      Research Laboratory (USA), the University of Florence (Italy), the
      University of Cambridge and the Rutherford Appleton Laboratory (UK). 

 NAME

      FREEBOUND

 PURPOSE:
      Calculates the free-bound (radiative recombination) continuum.

 INPUTS

      TEMP    Temperature in K (can be an array).

      WVL     Wavelength in angstroms (can be an array).

 OUTPUTS

      INT     Free-bound continuum intensity in units of 
              10^-40 erg cm^3/s/sr/Angstrom 
              ( integral(N_H N_e dh) in cm^-5) if a DEM is not defined. 

              If DEM values are defined, it is assumed that they are given
              as N_H N_e dh/dT.  The units are 10^-40 erg/cm^2/s/srAngstrom 

              If T is given as a 1-D array, then the output will be a 
              2-D array, with one element for each temperature and 
              wavelength (but also see SUMT).

 OPTIONAL INPUTS

      DEM_INT The intensity array is multiplied by a DEM number for 
              each temperature. DEM_INT needs to be of the same size 
              as TEMPERATURE. It is needed for the synthetic spectrum 
              routines.

      IZ     Only calculate continuum for the element with atomic 
             number IZ

      ION    (To be used in conjunction with IZ.) Calculated continuum 
             for a single ion (IZ, ION).

 KEYWORDS

      NO_SETUP If the procedure setup_elements has already been called 
               then the keyword /nosetup should be set to avoid 
               repeating this step

      MIN_ABUND If set, calculates the continuum only from those 
                elements which have an abundance greater than 
                min_abund.  Can speed up the calculations.  For 
                example:
                   abundance (H)  = 1.
                   abundance (He) = 0.085
                   abundance (C)  = 3.3e-4
                   abundance (Si) = 3.3e-5
                   abundance (Fe) = 3.9e-5

      PHOTONS  The output spectrum is given in photon units rather 
               than ergs.

      SUMT     When a set of temperatures is given to FREEBOUND, the 
               default is to output INTENSITY as an array of size 
               (nwvl x nT). With this keyword set, a summation over 
               the temperatures is performed.

      VERBOSE  Output information from FREEBOUND.

 COMMON BLOCKS

      ELEMENTS

 CALLS

      FREEBOUND_ION, SETUP_ELEMENTS, READ_KLGFB, GET_IEQ

 HISTORY

      Ver.1, 24-Jul-2002, Peter Young

      Ver.2, 26-Jul-2002, Peter Young
           revised call to freebound_ion; corrected ion fraction problem

       V 3, 25-May-2005, GDZ 
                  corrected routine header.

 VERSION     :  3, 25-May-2005

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	TWO_PHOTON

 PURPOSE:

	Calculate the 2 photon continuum from a hot, low density plasma.

       For the hydrogen isoelectronic sequence, A values
             Parpia, F. A., and Johnson, W. R., 1982, Phys. Rev. A, 26, 1142.
       and distribution function as a function of Z is taken from: 
             Goldman, S.P. and Drake, G.W.F., 1981, Phys Rev A, 24, 183

       For the helium isoelectronic sequence, A values are from:
             Drake, G.W.F., 1986, Phys. Rev. A, 34, 2871
       and the distribution function as a function of Z is taken from:
             Drake, G.W.F., Victor, G.A., Dalgarno, A., 1969, Phys. 
             Rev. A, 180, 25.
       in this paper the distribution is only given up to Z=10 but  
       extrapolation to higher Z appears to be OK.

       Note that, unlike the freefree and freebound routines, two_photon 
       requies the electron density to be specified. This is because there 
       is a call to pop_solver

 CALLING SEQUENCE:

       TWO_PHOTON,temperature, density, wavelength, intensity


 INPUTS:

	TEMPERATURE   Temperature in degrees Kelvin, can be a 1D array

       WAVELENGTH    Wavelengths in Angstroms.


 OPTIONAL INPUTS:

       DENSITY       Electron density in cm^-3, can also be a 1D array 
                     of the same size as Temperature. If there are several 
                     temperatures specified but only one density, then 
                     density is assumed the same at all temperatures.
                     If not specified, then default densities of 10^10 
                     electrons/cm^3 are assumed.

       DEM_INT An array of same length as TEMP which contains the 
               differential emission measure values at each temperature. 
               The emissivity at each temperature is multiplied by the 
               DEM value and the d(logT) value.
	
 KEYWORD PARAMETERS:

	NO_SETUP:   If the procedure setup_elements has already been called 
                   then the keyword /no_setup should be set to avoid 
                   repeating this step

       MIN_ABUND:  If set, calculates the continuum only from those 
                   elements which have an abundance greater than min_abund.  
                   Can speed up the 
                   calculations.  For example:
                   abundance (H)  = 1.
                   abundance (He) = 0.085
                   abundance (C)  = 3.3e-4
                   abundance (Si) = 3.3e-5
                   abundance (Fe) = 3.9e-5

       SUMT        If several temperatures have been specified, then /sumt 
                   will sum the emissivities over the different 
                   temperatures, giving an output INTENSITY that has the 
                   same size as WAVELENGTH.

       PHOTONS     If set the continuum emissivity is output in photon 
                   units rather than erg units.

       VERBOSE
 
 OUTPUTS:

	RAD         2 photon continuum intensity in units of
                   10^-40 erg cm^3/s/sr/Angstrom  per unit emission measure 
                   ( integral(N_H N_e dh) in cm^-5) if a DEM is not defined. 

                   If DEM values are defined, it is assumed that they are given
                   as N_H N_e dh/dT.  The units are 
                   10^-40 erg/cm^2/s/sr/Angstrom 

            If T is given as a 1-D array, then the output will be a 2-D array,
            with one element for each temperature and wavelength 
            (but also see SUMT).



 CALLS

       POP_SOLVER, SETUP_ION, SETUP_ELEMENTS, READ_MASTERLIST,
       CONVERTNAME

 COMMON BLOCKS:

       ELEMENTS, ELVLC, WGFA, UPSILON, PROTON

 EXAMPLE:

             > two_photon,1.e+6,3.e+10,wvl,int
             > two_photon,1.e+6,3.e+10,wvl,int,min_abund=3.e-5
             > two_photon,1.e+6,3.e+10,wvl,int,/no_setup

 PROGRAMMING NOTES

    For He 2-photon decays, the distribution function is from Table II 
    of Drake et al. (1969), except that the values have been divided by 
    the A-value from Drake (1986).


 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	February 2001:  Version 1.0

       Ver.2, 19-Dec-2001, Peter Young
           Now allows an array of temperatures.
           Added /SUMT keyword.
           Added DEM_INT= optional input.
           Switched to using spl_init & spl_interp for the spline fits.
           Corrected a small bug.

       Ver.3, 20-Dec-2001, Peter Young
           Corrected a bug related to density indices.

       Ver.4, 23-Apr-2002, Peter Young
           Added /photons keyword.

       Ver.5, 28-May-2002, Peter Young
           Corrected way in which DEM_INT is handled.

       V. 6, 28-May-2002, Giulio Del Zanna (GDZ)
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 
             Corrected the description of the  units and various
             inaccuracies in the header.
    
       V.7, 14-Aug-02, GDZ
             Added keyword VERBOSE

       V.8,  4-Oct-2003, GDZ
                  modified the input to POP_SOLVER, now it is dealt with an
                  input structure.

       V.9,  8-Jun-2004, EL
                  modified the input to POP_SOLVER, now it includes ion/rec

       V.10, 5-Jul-2005
                  corrected problems with the input structure for pop_solver

       v.11 29-Jul-2005, GDZ
                  fixed bug, only define ioneq_ionrec when files are
                  there (it was failing with neutrals)

 VERSION     :   11 29-Jul-2005

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME: SHOW_POPS
       
 PURPOSE:

	To display populations of significant levels in a CHIANTI ion 
	model

 CATEGORY:

       Scientific analysis

 EXPLANATION:

	Displays percentage level populations and level IDs for all levels 
	in the specified ion with populations greater than 0.01%. If the 
	temperature is not specified, then it is taken to be where the 
	maximum of the ionisation fraction is.

 CALLING SEQUENCE:

	SHOW_POPS, IZ, ION [, POPSTR, DENS= , TEMP= , /NOPROT,
                           RADTEMP= , RPHOT= , /ALL, /DIEL, PATH=,
                           IONEQ_FILE= , ABUND_FILE= ]

 EXAMPLES:

	show_pops,26,13,popstr
	show_pops,26,13,dens=7.5,temp=6.0,rphot=1.2

 INPUTS:

	IZ	The atomic number of the ion

	ION	The spectroscopic number of the ion (e.g., 12 = XII)

 OPTIONAL INPUTS:

	DENS	Logarithm of electron density

	TEMP	Logarithm of electron temperature. If not specified, then
               T_max of the ion is used

	RADTEMP	Specify background radiation temperature (default: 6000 K)

	RPHOT   Distance from the centre of the star in stellar radius units.
               I.e., RPHOT=1 corresponds to the star's surface. (Default is
               infinity, i.e., no photoexcitation.)

	PATH	Directly specify the path where the ion data is contained, 
		e.g., path='/home/other_data/fe_13'

       N_LEVELS  The size of the ion model is automatically determined 
                 from the information in the CHIANTI data files. Setting 
                 this keyword allows the number of levels in the model to 
                 be reduced. E.g., N_LEVELS=14 reduces the model to the 
                 first 14 levels given in the .ELVLC file.

       IONEQ_FILE To include proton rates in the level balance equations 
                  requires the number of density of protons to be known, 
                  and this requires an ion balance file and an abundance 
                  file to be specified, which are done through the 
                  IONEQ_FILE and ABUND_FILE keywords. If they are not set 
                  then the default files specified by !ioneq_file and 
                  !abund_file are used.

       ABUND_FILE See IONEQ_FILE.

       SUM_MWL_COEFFS  An array of coefficients of the same length as 
                       the array of temperatures. Electron and proton rate 
                       coefficients will be calculated at each temperature 
                       and then a weighted sum of the coefficients is 
                       performed using SUM_MWL_COEFFS. This allows 
                       non-Maxwellian energy distributions to be 
                       incorporated into the level balance equations.
                       If this keyword is set for an ion that has ionization
                       and recombination included in the level balance, then
                       these processes will be switched off for the
                       calculation since their rates implicitly assume a
                       single Maxwellian to describe the ion fractions of
                       the neighbouring ions.

       LEVEL   Allows the control of which level populations are displayed
               to the screen. If set to a positive scalar or array, then
               only those levels are printed. If it is set to a negative
               scalar (-n), then all level populations up to level n are
               printed. E.g., LEVEL=20 (only level 20); LEVEL=[5,7,20]
               (levels 5, 7 and 20); LEVEL=-20 (all levels up to level 20).

       RADFUNC         The name of a user-defined function that will generate
                       a radiation spectrum as a function of temperature. 
                       This radiation field will replace the black-body that
                       is assumed when using the RADTEMP keyword in the call
                       to pop_solver.

; OPTIONAL OUTPUTS

       POPSTR  Send level population information to a structure. POPSTR has 
               the tags:
               .dens    Density (cm^-3)
               .temp    Temperature (K). Can be an array if SUM_MWL_COEFFS=
                        is used.
               .radtemp RADTEMP. Set to -1 if RADTEMP not 
                        set.
               .rphot   RPHOT value. Set to -1 if RPHOT not set.
               .proton  String set to 'yes' if proton rates included, 'no' 
                        otherwise
               .version CHIANTI version used to derive populations.
               .date    Date and time at which structure created.
               .level   Structure containing level information. Tags are:
                  .index   CHIANTI level index
                  .term    String containing level identifier.
                  .pop     Population of level
               .sumtst  Set to 1 if the SUM_MWL_COEFFS keyword has been used.
                        Set to 0 otherwise.
               .sum_mwl_coeffs Contains SUM_MWL_COEFFS. Set to -1 if sumtst=0.

 KEYWORDS:

	ALL	Show populations for all levels.

       NOPROT  If set, then the default setting will be NOT to use 
               proton rates. This can be changed within the routine.

       DIEL    Use the dielectronic recombination files. E.g., for Fe XXII, 
               the routine will read in the fe_22d.* files instead of the 
               fe_22.* files.

 COMMON BLOCKS:

	ELVLC, WGFA, UPSILON, RADIATIVE, PROTON, ELEMENTS

 CALLS:

	ZION2FILENAME, POP_SOLVER, SETUP_ION, READ_IONEQ,
       READ_ABUND, PROTON_DENS, CONCAT_DIR

 HISTORY:

	Ver 1, PRY 22-Sep-97
	Ver.2, PRY 5-Sep-98  - added call to choose_ioneq
	Ver.3, PRY 23-Apr-99 - calls pop_solver now; added DENS keyword
	Ver.4, PRY 18-Dec-99 - added deu to upsilon common block to be 
			consistent with main Chianti routines.
       Ver.5, PRY 7-Aug-00  - added /DIEL keyword to allow populations of 
                       the dielectronic recombination files to be studied.
                       Also changed elvlc common block to match new 
                       version of pop_solver.
       Ver 6, PRY 10-Oct-00 - now calls setup_ion to read ion data
       Ver 7, PRY 12-Nov-01 - modified for proton rates, photoexcitation,
                       and 9 pt splines.
       Ver 8, PRY 9-Dec-01  - completed modifications for v4 of CHIANTI.

       V.  9, 25-May-2002, Giulio Del Zanna (GDZ) 
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 
                   Now we only call zion2filename

       V. 10, 9-Aug-2002, Peter Young
                   corrected !ioneq_file problem

       V. 11, 12-Aug-2002, Peter Young
                   added POPSTR output, and tidied up header.

       V. 12, 4-Oct-2003, GDZ
                  modified the input to POP_SOLVER, now it is dealt with an
                  input structure.

       V 13, 4-May-2005, Enrico Landi (EL)
                  Modified in order to include ionization and recombination
                  data in the input to POP_SOLVER

       V.14, 26-May-2005, Peter Young (implemented by GDZ)
                  added SUM_MWL_COEFFS optional input for allowing
                  non-Maxwellian distributions to be considered.

                  added LEVEL= optional input to only print the populations of
                  a few levels.

       V.15, 5-Jul-2005, Peter Young
                  added RADFUNC= and /QUIET keywords

 VERSION     :   15, 5-Jul-2005

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	PLOT_POPULATIONS

 PURPOSE:
	plot the population of a number of the lowest levels as a function of 
       electron density for a specific temperature

 CATEGORY:

	science.

 CALLING SEQUENCE:

       PLOT_POPULATIONS,Ion,T,Nlevels


 INPUTS:

       Ion:  CHIANTI style name for the ion, i.e., 'c_6' for C VI
       T:  electron temperature (K)


 OPTIONAL INPUT:
       Nlevels:  the number of levels for which populations are plotted
                 starts from level 1 (the ground level)

	
 KEYWORD PARAMETERS:

	OUTFILE:   the (optional) name of the output file where the listing 
                  is produced
	PSFILE:    the (optional) name of the output file where a postscript 
                  plot produced

	RADTEMP	Specify background radiation temperature (default: 6000 K)

	RPHOT   Distance from the centre of the star in stellar radius units.
               I.e., RPHOT=1 corresponds to the star's surface. (Default is
               infinity, i.e., no photoexcitation.)

       NOPROT  If set, then the default setting will be NOT to use 
               proton rates. This can be changed within the routine.

               NOT_INTERACTIVE Avoid interactive use.

 OUTPUTS:


 COMMON BLOCKS:

	common elvlc,l1a,term,conf,ss,ll,jj,ecm,eryd,ecmth,erydth,eref
       common wgfa, wvl,gf,a_value
       common upsilon,t_type,c_ups,splups

 CALLS

       POP_SOLVER, ION2SPECTROSCOPIC, ION2FILENAME, READ_IP,
       CONVERTNAME, READ_ELVLC, READ_WGFA2, READ_SPLUPS

 EXAMPLE:

 to plot populations of the 5 ground configuration levels of Fe XIII
 and store these values in a file 'Fe_XIII.lis' for a temperature of 1.5 MK

             > plot_populations,'fe_13',1.5e+6,5,outfile='Fe_XIII.lis'

 MODIFICATION HISTORY:

 	Written by:	Ken Dere
	March 1996:     Version 2.0
       November 1997:  Ken Dere, added psfile keyword
       September 1999:  Ken Dere, for Version 3, 
       14-Jul-2000     Peter Young, now calls pop_solver
	Version 6, 21-Dec-2000, William Thompson
		Modified for better cross-platform capability.

       V. 7, 21-May-2002, Giulio Del Zanna (GDZ), modified the plotting bit
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

       V 8, 15-July-2002, GDZ 
         Added keyword  not_interactive

       V 9, 4-Oct-2003, GDZ
                  modified the input to POP_SOLVER, now it is dealt with an
                  input structure.

       V 10, 4-May-2005, Enrico Landi (EL)
                  Modified in order to include ionization and recombination
                  data in the input to POP_SOLVER, now it allows choice of .ioneq
                  file needed to include ionization and recombination.

       V 11, 12-Aug-2005, GDZ 
                  The number of levels is now optional. Also, a check that the
                  number of levels must be less than the levels in the file is
                  now enforced.


 VERSION     :   11, 12-Aug-2005

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME: POP_PLOT
       
 PURPOSE:

	To compute n_j A_ji / N_e for a selected transition(s) and plot it
	against N_e. If it is insensitive to N_e, then the line(s) is 
	suitable for emission measure analysis.

 CATEGORY:

       Atomic data analysis

 EXPLANATION:

	The routine calls EMISS_CALC to give values of DE*n_j*A_ji at the 
	temperature TEMP and densities from 10^8 to 10^12. You are then 
	asked to select which transition(s) you are interested in. (If 
	more than one line is selected, the lines are blended.) 
	DE*n_j*A_ji/N_e is then plotted against density.

	If TEMP is not specified, then the temperature at which the 
	ionisation fraction has its maximum is calculated. For the iron 
	ions, the ion balance calcs of Arnaud & Raymond are used, 
	otherwise Arnaud & Rothenflug are used. If TEMP is specified, 
	and the value is less than 20, then it is assumed that the log 
	of the temperature has been specified.

	In emission measure work it is important to isolate lines for 
	which DE*n_j*A_ji/N_e is insensitive to density. If only such lines 
	are used, then the derived emission measure curve is independent 
	of density.

 CALLING SEQUENCE:

       POP_PLOT, IZ, ION, WRANGE=WRANGE, [TEMP=TEMP, /QUICK, DATA=DATA, $
				DENS_RANGE=DENS_RANGE, DILUTE=DILUTE]

 EXAMPLES:

	POP_PLOT, 26, 14, WRANGE=[330,360]

	- 3 lines should appear in the widget. Selecting 334.17 should show 
	a curve that falls off with density. Choosing 353.83 shows a curve 
	that rises with density. By selecting a blend of the two lines, 
	the curve will be insensitive to density, telling us that only a 
	blend of 334.17 and 353.83 is suitable for emission measure work.

	POP_PLOT, 8, 4, WRANGE=[550,560], TEMP=6.0, /QUICK, DENS_RANGE=[6,10]

	- O IV is a member of the boron sequence, and so calculations take a 
	lot longer. Giving the QUICK keyword speeds things up. The 
	temperature is well away from the T_max of the ion

 INPUTS:

	IZ	The atomic number of the ion

	ION	The spectroscopic number of the ion (e.g., 12 = XII)

 OPTIONAL INPUTS:

	DILUTE	Used to set radiative dilution factor. (Default: 0.0)

	TEMP	The temperature at which calculations are required. Usually 
		this will be the Tmax of the ion.

	DENS_RANGE  The default density range is log Ne = 8 to 12. By 
		    inputting two integers, a different range can be chosen.

	WRANGE  Wavelength range from which lines are required. If not 
		given, then the user is allowed to choose from the complete 
		set of lines for the ion.

       ABUND_FILE  The name of a CHIANTI abundance file. This is used for 
               calculating the proton to electron ratio. Default is 
               !abund_file.

       IONEQ_FILE  The name of a CHIANTI ion balance file. This is used for 
               calculating the proton to electron ratio and evaluating 
               the T_max of the ion. Default is !ioneq_file.

       RADTEMP The blackbody radiation field temperature (default 
               6000 K).

       RPHOT   Distance from the centre of the star in stellar radius 
               units. I.e., RPHOT=1 corresponds to the star's surface. 
               (Default is infinity, i.e., no photoexcitation.)

 OPTIONAL OUTPUTS:

	DATA:	An array that contains the data that is plotted: data(*,0) 
		contains
		the densities, while data(*,1) contains the Y-axis values.

 KEYWORDS:

       NOPROT  If set, then the default setting will be NOT to use 
               proton rates. This can be changed within the routine.

	QUICK:	The density range over which the calculations are done is 
		8 to 12 in 0.2 intervals. This keyword forces the 
		calculations to be done at 0.5 intervals.

 CALLS:

	EMISS_CALC, EMISS_SELECT, READ_IONEQ

 HISTORY:

	Ver.1, PRY 28-Jul-97.
	Ver.2, PRY 23-Sep-97 - added DILUTE keyword for photo-excitation
	Ver.3, PRY 30-May-98 - added DENS_RANGE
	Ver.4, PRY 5-Sep-98  - added call to choose_ioneq
	Ver.5, PRY 7-Apr-99  - tidied up, and introduced call to emiss_select
       Ver.6, PRY 7-Dec-01  - modified for v.4 of CHIANTI

       V. 7, 21-May-2002, Giulio Del Zanna (GDZ) 
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

       V.8, 06-Aug-02 GDZ
              added ABUND_FILE to the call to emiss_calc (was missing).
              Changed the use of CHIANTI system variables. 


 VERSION     : 8,  06-Aug-02

 NAME

      POP_PROCESSES

 PROJECT

      CHIANTI

 PURPOSE:

      Outputs to the screen the contributions of the different physical 
      processes to the population of the specified level within the ion. 


      E.g., for Fe XIII, level 4, the output is:

      Population leaving level 4
        rad. decay:     1.51e+01     39.17%
        e de-exc:       3.56e-01      0.92%
        e exc:          2.28e+01     59.12%
        p de-exc:       2.63e-01      0.68%
        p exc:          4.05e-02      0.11%
        stim. emiss:    0.00e+00      0.00%
        photoexc:       0.00e+00      0.00%
                        --------
                 TOTAL  3.85e+01
      
      Population entering level 4
        rad. decay:     3.59e+01     93.19%
        e de-exc:       3.81e-02      0.10%
        e exc:          1.46e+00      3.79%
        p de-exc:       3.18e-03      0.01%
        p exc:          1.12e+00      2.91%
        stim. emiss:    0.00e+00      0.00%
        photoexc:       0.00e+00      0.00%
                        --------
                 TOTAL  3.85e+01

      which shows that the level population is dominated by electron
      excitation and cascading into the level, and by radiative decay
      out of the level.

      Note that the rates for each physical process are multiplied by the 
      population of originating level (this results in the totals for 
      entering and leaving the level to balance).

      For some ions, ionization and recombination are additional processes
      included when working out the level balance. Because of the way these
      processes are included (see the v.5 paper for details), the populations
      entering and leaving some levels *will not balance*.

 INPUTS

      IZ      The atomic number of the ion

      ION     The spectroscopic number of the ion (e.g., 12 = XII)

 OPTIONAL INPUTS

      LEVEL   The ion level for which information is required.

      DENS    Electron density at which rates calculated (units: cm^-3).
              If not specified, a value of 10^10 is assumed.

      TEMP    Temperature at which rates calculated (units: K). If not set,
              then T_max of the ion is used

      PATH    If the ion data-files are not in the CHIANTI directories, 
              then PATH allows you to choose an alternative location.

      RPHOT   Distance from the centre of the star in stellar radius units.
              I.e., RPHOT=1 corresponds to the star's surface. (Default is
              infinity, i.e., no photoexcitation.)

      RADTEMP Specify background radiation temperature (default: 6000 K)

      N_LEVELS Restrict the ion model to this number of levels. E.g., if
               the CHIANTI model contains 40 levels for the ion, then
               setting N_LEVELS=12 reduces the model to 12 levels.

      RADFUNC  The name of a user-defined function that will generate
               a radiation spectrum as a function of temperature. 
               This radiation field will replace the black-body that
               is assumed when using the RADTEMP keyword in the call
               to pop_solver.

 KEYWORDS

      NOPROT  If set, then the default setting will be NOT to use 
              proton rates. This can be changed within the routine.

 CALLS

      R2W, ZION2FILENAME, PROTON_DENS, POP_SOLVER, SETUP_ION

 EXAMPLES

      One can compare the effect of cascading on a level population by using
      the N_LEVELS keyword. Consider the case of Fe XIV:
        IDL> pop_processes,'fe_14',lev=5
        IDL> pop_processes,'fe_14',lev=5,n_levels=12
      With the first call there are two dominant terms to the population
      entering level 5: approximately 47% for radiative decays (cascading)
      and 53% for electron excitation. Setting n_levels=12, one finds that
      the cascading contribution disappears as there are no longer any
      high-lying levels that cascade into level 5. The cascading provides
      a strong contribution to the population of this level.

 HISTORY

      Ver.1, 11-Sep-2002, Peter Young
      Ver.2, 15-Jan-2004, Peter Young
          modified call to pop_solver following recent revision to
          pop_solver; changed input from IZ,ION to IONNAME to match other
          CHIANTI routines
      Ver.3, 26-May-2005, Peter Young
          changed TEMP and DENS keywords
      Ver.4, 10-Jun-2005, Peter Young
          added common block for ionization/recombination data and modified
          INPUT structure.
      Ver.5, 14-Jun-2005, Peter Young
          routine now prints the percentage contribution of each process;
          added N_LEVELS= keyword
      Ver.6, 1-Jul-2005, Peter Young
          added warning for ions with ionization/recombination

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 

 NAME:
	RAD_LOSS

 PURPOSE:

       Calculates energy loss rate by free-free (ff), radiative 
       recombination (fb) and by line (bound-bound) radiation.

 CATEGORY:
	
	synthetic spectra

 CALLING SEQUENCE:

       RAD_LOSS,Temperature,Loss_rate


 INPUTS:

	None:  The user will select an elemental abundance file and a 
              ionization equilibrium file through widgets.

  KEYWORDS:

       Pressure:  pressure in emitting region (cm^-3 K)
                  density=pressure/temperature(K)

       Density:   density (cm^-3), constant for all temperatures
                  if neither density or pressure is set, then a default 
                  constant density of 10^10 cm^-3 is used.

       Psfile:    to create a postscript plot of the radiative loss in 
                  the file specified by the name assigned to 'Psfile'

       Outfile:   name of an ascii file where the radiative loss rate 
                  as a function of temperature is output
                   
	RADTEMP	Specify background radiation temperature (default: 6000 K)

	RPHOT   Distance from the centre of the star in stellar radius units.
               I.e., RPHOT=1 corresponds to the star's surface. (Default is
               infinity, i.e., no photoexcitation.)

       NOPROT  If set, then the default setting will be NOT to use 
               proton rates. This can be changed within the routine.



 OUTPUTS:

       Temperature:  array of temperatures (K)
       Loss_rate:    energy loss rate in erg cm^3 s^-1


 PROCEDURE:


  if keyword pressure is set then calculations performed at constant pressure
  if keyword density is set then calculations performed at constant density
  otherwise, density is set to 1.e+10
  
  pressure = density * temperature  (cm^-3 K)

	the user will be asked to select an abundance file and a 
       ionization balance file.

 EXAMPLE:

       > rad_loss,t,r


 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	January 1999:  version 1, adopted from synthetic.pro
	Version 2, 21-Dec-2000, William Thompson
		Modified for better cross-platform capability.

       Ver.3, 6-Dec-2001, Peter Young
               Added /noprot, radtemp and dilute keywords.
               Removed elvlc, wgfa and upsilon common blocks.
               Removed calls to read_ip and read_masterlist (not needed).

       Ver.4, 8-Jul-2003, Peter Young
               Updated routine header (no changes to code).

       V 5, 25-May-2005, GDZ 
                  corrected routine header.

 VERSION     :   5, 25-May-2005, GDZ 

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 
                   
 Name        : PLOT_IONEQ
               
 Purpose     : Plots the ionisation equilibrium values for an element.

 Explanation : 
               
 Use         : IDL> plot_ioneq, element [ ion=ion]
    
 Inputs      : element - the element name
               
 Opt. Inputs : Ion (as keyword)
               
 Outputs     : None
               
 Opt. Outputs: a postscript file.
               
 Keywords    : ION_RANGE - specify range of ions. E.g., ion_range=[5,8] 
                    means V to VIII inclusive.
               IONEQ_NAME:  Name of the ionization equilization name to use.
                    If not passed, then the user is prompted for it.
               NOT_INTERACTIVE Avoid interactive use.

 Calls       :  Other CHIANTI routines

 Common      :
               
 Restrictions:  None
               
 Side effects:  None
               
 Category    :  Spectral
               
 Prev. Hist. :  None

 Written     :  C D Pike, RAL, 9-Jun-97
               
 Modified    :  V.2. Update element list. modified definition of XUVTOP, and
               allowed selection of ionization eq. file and creation of
               postscript file. 
               Giulio Del Zanna  (DAMTP) 10-Oct-2000 

       V.3, Giulio Del Zanna (GDZ)
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

       V 4, 15-July-2002, GDZ 
         Added keywords ioneq_name, not_interactive

       V.5, 9-Feb-2005, Peter Young
            Changed ion= keyword to ion_range=

 VERSION     :    5, 9-Feb-2005

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 

 Name        : MAX_TEMP
               
 Purpose     : Calculates temperature at max ionisation ratio for an ion

 Explanation : 
               
 Use         : IDL> print,max_temp(ion)
    
 Inputs      :  ion - the specific ion in the form eg 'Fe_XII' or 'Fe XII'
               
 Opt. Inputs :  None
               
 Outputs     :  Function returns log of max temperature
               
 Opt. Outputs:  None
               
 Keywords    :  ALL - if set produces a plot of all temperatures

 Calls       :  Other CHIANTI routines

 Common      :
               
 Restrictions:  None
               
 Side effects:  None
               
 Category    :  Spectral
               
 Prev. Hist. :  None

 Written     :  C D Pike, RAL, 9-Jun-97
               
 Modified    :  V.2 Update element list.  CDP, 18-Jun-99 
                V.3 modified definition of XUVTOP, and allowed selection of
                ionization eq. file. Giulio Del Zanna (DAMTP) 10-Oct-2000

                V.4, Giulio Del Zanna (GDZ)
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

 VERSION     :   4, 21-May-2002, GDZ 

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 

                   
 Name        : CHIANTI_DEM
     		          
 Purpose     : Calculates the Differential Emission Measure DEM(T) using 
		the CHIANTI database, from a given set of observed lines.
		Constant pressure or density can be used.

 Category    : diagnostic analysis
               
 Explanation : This routine has several options, all in the form of keywords.
 		First, the input file with the observed fluxes is read.
		THE FIRST TIME YOU USE THIS ROUTINE
		you'll have to do the calculation of the contribution
		functions G(T), so the routine GET_CONTRIBUTIONS will come 
		into play. You'll have to specify the value of the 
		pressure or density, and  you'll be asked to select an  
		ionization equilibrium file and an abundance file.
		GET_CONTRIBUTIONS searches the CHIANTI database (ion per ion) 
		for all the theoretical lines corresponding to the observed 
		lines, i.e. that lie in a OBS_WVL(i) +/- DELTA_LAMBDA_OBS(i) 
		interval centered on the observed wavelength OBS_WVL(i).
		The routine calculates the C(T) values (G(T)=Ab(element)*C(T))
		for the temperature interval log(T)= 4.0 - 8.0  
		with steps of log(T) = 0.1 .
		You can either select a constant pressure OR a constant 
		density for all the lines; if you select a constant pressure,
               for each ion the contribution function is calculated at an 
               electron density N_e equal to the ratio of the pressure 
               and the temperature of maximum ionization fraction:  
               C=C( T, N_e= P/T_ion )  
               The C(T) values are stored by GET_CONTRIBUTIONS in the output 
		file OUTPUT.CONTRIBUTIONS that can be used later to calculate
		the DEM, changing various parameters,
		without having to start again and read the CHIANTI database,
		which can take long time.

		In the case no theoretical lines corresponding to an observed
		line are found, the routine writes the wavelength of the line
		(to be excluded from the fit) in the array
		EXCLU_OBS_WVL_NO_TEO. The lines with no theoretical 
		counterparts are then automatically  excluded from the fit by 
	 	CHIANTI_DEM. You might consider the possibility to start again
		incrementing the DELTA_LAMBDA_OBS, to see if there are 
		theoretical lines in the vicinity.
		Note: if you want to exclude some of the observed lines from 
		the fit, you just have to use the keyword EXCLUDE_OBS_WVL, 
		BUT  GET_CONTRIBUTIONS will store anyway the results (if any)
		in the C(T) file.

		After having excluded the lines in EXCLUDE_OBS_WVL, 
		any *.abund file present in the CHIANTI database or in 
		the working directory can be selected, and eventually edited,
		if you like to change some abundances. 
		Then the $G(T)$ are calculated, multiplying each theoretical
		line by the abundance factor. Then the
		theoretical lines contributing to each blend are sorted by
		intensity and then their G(T) can be plotted if the keyword
		PLOT_GT is activated. It is recommended to do this the first 
		time, to check if there are some observed lines terribly 
		blended with lines of other elements, in which case it is
		better to exclude them with a second run (if you are not 
		sure about the abundances).
		Then the G(T) for each blend are summed and plotted.
		Then  the fit starts calling DEM_FIT. 
		A series of parameters can change the 
		result (DEM), especially the number and position of the mesh
		points of the spline that represents the DEM. The keyword
		MESH_POINTS serves for this purpose. 
		The other keywords that control the fit are N_ITER, DCHISQ_M.
   		At the end of the fit, the files OUTPUT.DEM and OUTPUT.GENERAL
		are created.



 Use         : IDL>chianti_dem,output='serts89',file_input='serts89.obs',$
				pressure=3.e15


 Examples    : 
		Assume you have a file input 'serts89.obs' like this:
		
		243.031   491.    97.    0.1  He II
		256.323   1580.   186.   0.1  He II b
		315.024   253.    31.    0.1  Mg VIII
		335.401   10400.  1650.  0.1  Fe XVI
		319.839   113.    14.    0.1  Si VIII
		356.027   218.    25.    0.1  Si X 
		
		IDL>chianti_dem,output='serts89',file_input='serts89.obs',$
		   pressure=3.e15,cut_gt=1e-30,/plot_gt

		After having selected the  ionization file,
		the C(T) (with MAX(C(T)) gt 1e-30)  are stored in the file
		'serts89.contributions'. Then select one of the abundance 
		files. 
		Have a look at the plots of the  G(T), and annotate
		if there is a line you want to exclude, let's say the second.
		Have a look at the DEM obtained ('serts89.dem') and at 
		the details contained in the file 'serts89.general'. 
		Maybe there is another line you want to exclude, let's say 
		the last one. Maybe you want to change the mesh points, too.
		So run
		IDL>chianti_dem,output='serts89_2',file_input='serts89.obs',$
		file_gt='serts89.contributions',$
		exclude_obs_wvl=[243.031,356.027 ],$
		mesh_points= [4.5,5.,5.5,6.2,7.5]
		
		The files 'serts89_2.dem' and 'serts89_2.general' will be
		created. They have the essential information about what you 
		did.

    
 Inputs      : various, all in form of keywords. The required ones are 
		OUTPUT and FILE_GT (or  PRESSURE/DENSITY)
               
               
 Opt. Inputs : various... see the software note.
               
 Outputs     : OUTPUT.CONTRIBUTIONS  
		Created only if the keyword FILE_GT is NOT set. 
		Is the file where all the contribution  functions G(T) are 
		stored. In the first two lines  the ionization equilibrium 
		file name, and the constant value of pressure or density 
		adopted are reported. Then for each line you have reported  
               the observed wavelength, the theoretical one, the element and
		ionization stage, then the C(T) values. At the end the 
		specification for each transition.

		OUTPUT.DEM
		Is the file where the log T and log DEM values are 
		written, with a format suitable 
		as input for the DMM_SS procedure,that calculates the 
		synthetic spectrum. At the end some info on how it was 
		calculated are printed.

		OUTPUT.GENERAL
		Is the file where general information is stored.
		The abundance file, the ionization equilibrium file and the
		constant value of pressure or density  used are reported. 
		Then there is one line for each
		observed line, with the provisional identification, the 
		observed wavelength, the observed flux, the theoretical one
		(corresponding to the DEM), the error on the flux,
		the square of the difference between the theoretical and the 
		observed fluxes divided by the error (this number should be 
		close to zero if the line is well reproduced), and finally
		the ratio of the theoretical flux versus the observed one 
		(which should be close to 1).
		After this line, there is one line per each theoretical line
		contributing to the blend, with the identification, the 
		theoretical wavelength, the configuration and terms, and the
		contribution to the total theoretical flux (in percentage) 
		of each line in the blend.

		OUTPUT.OUT
		This file , toghether with OUTPUT.DEM , 
		can be used to reproduce the results  using 
		user-written software. See the software notes.
		The ouput has this format: 
		format='(a20,1x, 1f10.3,1x, 3e10.3, 1x,  f4.2,1x,f6.3)'	
	
 Opt. Outputs:
		An abundance file with the modifications inserted.
	
		Postscript files of the G(T).
	
		A postscript file with the DEM (OUTPUT.DEM.PS)
		
               A postscript file with other plots too (OUTPUT_4PLOTS.PS)

 Keywords    : 


	ARCSEC: 
		optional. If set, it means that the intensities in the input
		file are per arcsec-2 .
		These intensities are then  converted to 
		 sterad-1 .

	CUT_GT:	
		optional. If set, only the those theoretical lines that
		have a MAX(C(T))  greater than the value set, are kept; 
		it is useful to set this value in order to reduce the number 
		of lines in the file where the C(T) are stored.;  
		if not set, a default value of 1e-30 is adopted.

	DCHISQ_M:
		optional. If not set, a default value of DCHISQ_MIN=1.e-5 
		is assumed. For each iteration, the CHISQ and it's variation 
		are calculated. As long as the iteration achieves an
		improvement in CHISQ greater than  DCHISQ_MIN , another 
		iteration will be performed.

	DEM_FILE:
		optional.If set (,/DEM_FILE) you have to choose a DEM file to 
		be used as a start, instead of the default constant value of 
		10.^22.
		You can either choose one of the files in the CHIANTI database
		or any you have in the working directory. 
		The values in the file are marked as crosses, the mesh points
		are marked with triangles.

	DENSITY : 
		the value of the density (Ne). Required if you do NOT have
		already the contribution  functions G(T). 

	EXCLUDE_OBS_WVL:
		optional.
		If set, you can  exclude some of the observed lines from 
               the fit. Note that even if you set this keyword and run 
		GET_CONTRIBUTIONS all the theoretical lines found corresponding
		to all the lines in the input file are written in the C(T) 
		file. It is only in the fit that the lines are excluded.

	FILE_GT:
		optional.
		If NOT set, the routine GET_CONTRIBUTIONS is called.
               If set, it has to specify the name of the file created by 
		GET_CONTRIBUTIONS, where all the contribution  functions G(T) 
               are stored. In the first two lines the ionization equilibrium 
		file name, and the value of the pressure or density 
               adopted is reported. Then for each line you have reported  
               the observed wavelength, the theoretical one, the element and
               ionization stage, then the C(T) values. At the end the 
               specification for each transition.

	FILE_INPUT:
		optional.
 		if set, you are not requested to select the observation file
		using a widget-type search.
		The input file  must contain 5 columns, unformatted:
		1)the observed wavelength (A)
		2)the observed flux in erg cm-2 s-1 st-1
		3)the corresponding error on the flux in erg cm-2 s-1 st-1
		4)half the width (A) of the range (centered on the observed 
		  wavelength) where you want to look for the corresponding 
		  theoretical lines. A value of HWHM or more would do.
		5)The identification, written as string (max 20 characters)

	MESH_POINTS:    	
		optional. It is a vector that specifies the mesh points for the
		spline that represent the fitted DEM, in log(T).
		If not set, the default values 
		[4.,4.5,5.,5.5,6.,6.5,7.,7.5,8.0] are assumed.

	N_ITER:
		optional.It is the number of iterations of the fitting routine.
		If not set, a default value of 20 is assumed. 
		Changing this value alone might not affect the fit, since 
		also the value of DCHISQ_MIN is checked during the fit.

	N_MATCHES:   
		optional.          
		In the unlikely event that more than 50 (default value for 
		N_MATCHES) theoretical lines corresponding to an observed
		line are found, the routine stops; in this case, you have to 
		start again setting N_MATCHES equal to a greater number. 

	OUTPUT  :
		required.
	  	It is the output name. Suffixes will be added when creating 
		the various outputs.

	PHOT:
		optional.
		If set, it means that in the input file the intensities
		are in photons instead of ergs. 

	PLOT_GT:
		optional.
		If set (,/PLOT_GT),  plots of the  G(T) for each 
		observed line not excluded are created.

	PRESSURE:     		
		the value of the pressure (Ne T). Required if you do NOT have
		already the contribution  functions G(T).

	QUIET:
		optional. Set to avoid various messages and the details of the 
		result.

 Calls       : GET_CONTRIBUTIONS
		DEM_FIT
		ZION2SPECTROSCOPIC
		print2d_plot
		
 Common      : obs, 	obs_int,obs_sig,n_obs
		obs_o,	obs_wvl,obs_id,obs_delta_lambda
 		dem, 	d_dem_temp,dem_temp,log_dem_temp,log_t_mesh,log_dem_mesh
		contr,	ch_tot_contr
		ab,	abund_name,abund_info,xuvtop,ioneq_name

		these are the commons with GET_CONTRIBUTIONS.PRO:

		various,	exclu_obs_wvl_no_teo,const_net,$
		 dem_temp_min,dem_temp_max,n_dem_temp,$
		 ch_wvl,ch_l1,ch_l2,ch_id,ch_z,ch_ion,ch_contr_wa,$
		 ch_pop,ch_contr_list,	 ch_term,ch_n_contr

 Restrictions: 
		In the unlikely event that more than 50 (default value for 
		N_MATCHES) theoretical lines corresponding to an observed
		line are found, the routine stops; in this case, you have to 
		start again setting N_MATCHES equal to a greater number. 

		Also, if the starting DEM values are not proper, or you 
		don't have enough constraints at lower and higher temperatures,
		you might get "strange" results, and should consider using 
		different starting values.

		Of course you need to have the enviroment variable CDS_SS_DERE
		pointing to the CHIANTI database top directory.

               
 Side effects: None known yet.
               
 Category    : spectrum
               
 Prev. Hist. :
       Written by Ken Dere (NRL) as part of the CHIANTI package 
       in collaboration with Brunella Monsignori Fossi, Enrico Landi
       (Arcetri Observatory, Florence), Helen Mason and Peter Young
       (DAMTP, Cambridge Univ.). Incorporated into the CDS software.  

 Written     : 
       V. 1.0  5 November  1997 Giulio Del Zanna (GDZ), 
	UCLAN  (University of Central Lancashire, UK)


 Modified    : Removed the print2d_plot subroutine. Increased the default value
               of N_MATCHES from 20 to 50.  Changed way to deal with xuvtop.
               GDZ, 31-Oct-2000

 Version     : 2.0 GDZ, DAMTP,  31-Oct-2000

              V.3, Giulio Del Zanna (GDZ)
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

 VERSION     :  3, 21-May-2002, GDZ 

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	PLOT_DEM

 PURPOSE:

	To plot differential emission measure (DEM) values

 CATEGORY:

	Widgets.

 CALLING SEQUENCE:

       PLOT_DEM,filename


 INPUTS:

	filename:  the name of the DEM file to be plotted.  The file must b
                  in the standard CHIANTI format for DEM files.  If filename 
                  is a blank string ('') then an interactive window will come 
                  up to allow the user to select a DEM file from the CHIANTI 
                  DEM directory or some other directory.	

	
 KEYWORD PARAMETERS:

	PSFILE:	If set, the a postscript plot will be place in the 
               file 'psfile' specified by the user


 OUTPUTS:

       None, other than a plot




 EXAMPLE:

             > plot_dem,'ademfile.dem'
         or
             > plot_dem,''

 MODIFICATION HISTORY:

 	Written by:	Ken Dere
	June 1998:     Version 1.0
	Version 2, 21-Dec-2000, William Thompson, GSFC
		Modified for better cross-platform graphics capability

       V.   3, 21-May-2002, Giulio Del Zanna (GDZ) 
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

 VERSION     :   3, 21-May-2002 

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME: INTEGRAL_CALC
       
 PURPOSE:

       To compute the atomic data integral for use in column or volume
	emission measure work.

 CATEGORY:

       Scientific analysis

 EXPLANATION:

 	Defining

	G(T) = 0.83 * Fr(T) * N_j * A_ji / N_e

	where Fr(T) is the ionisation fraction (e.g., from Arnaud & 
	Rothenflug), N_j the relative population of level j, A_ji the 
	A-value for the j->i transition and N_e the electron density. The 
	0.83 is the ratio of hydrogen to free electrons, which is constant 
	above around 10^4 K. This function is sharply-peaked at a 
	temperature T_mem (the temperature of maximum emission, which can 
	be different from the temperature of maximum ionisation, T_max) 
	and so an oft-used approximation is to take G(T) constant in the 
	range log T_mem - 0.15 to log T_mem + 0.15 and zero outside. The 
	value of the constant, which we call C_lambda here, is then given 
	by

	C_lambda =    integral { G(T) dT }
                     --------------------
                  T_mem * (10^0.15 - 10^-0.15)

	If EM(s) is the column emission measure, F the flux (erg cm-2 s-1)
	in a line lambda, Ab the abundance of the element and DE (erg) the
	energy for the transition, then:

	F = DE * Ab * C_lambda * EM(s)

	If we are dealing with intensities I (erg cm-2 s-1 sr-1) then:

	4pi * I = DE * Ab * C_lambda * EM(s)

	This program extracts the ionisation balance and emissivities from 
	the CHIANTI database and calculates C_lambda for all lines in the 
	specified wavelength interval WRANGE by integrating over 
	0.02 dex temperature intervals, using the IDL INT_TABULATED function.

	The C_lambda functions for all the lines in the selected wavelength 
	range WRANGE are displayed as well as the temperature of maximum 
	emission (T_mem), DE*C_lambda and 4pi/(DE*C_lambda). These latter 
	two quantities are useful for the emission measure analysis.

	Any combination of the displayed lines can then be blended and the 
	corresponding quantities for the blend will be displayed.

	The function Fr(T) * N_j * A_ji can also be plotted at this stage.

 CALLING SEQUENCE:

       INTEGRAL_CALC, IZ, ION, [WRANGE=WRANGE, /CHOOSE, DENS=DENS]

 EXAMPLES:

	INTEGRAL_CALC, 26, 13, WRANGE=[200,205], /CHOOSE

	INTEGRAL_CALC, 14, 10, WRANGE=[250,270], DENS=10.

 INPUTS:

	IZ:	The atomic number of the ion
	ION:	The spectroscopic number of the ion (e.g., 12 = XII)

 OPTIONAL INPUTS:

	DENS:	The density at which the emissivities are calculated 
		(default=10.)
	WRANGE: Wavelength range for which C_lambda functions are 
		calculated. If not given, then the 10 strongest lines 
		are printed.
	INDEX:	Particular elements in the emissivity structure can be 
		selected with INDEX. This allows integral_calc to be run 
		'silently'. The output is contained in the OUTSTR structure. 
		If index is given as, e.g., [7,8], then the C_lambda 
		functions for these two lines are summed and output.
	PATH:	Directly specify the directory path where the Chianti data 
		for the ion is found

       ABUND_FILE  The name of a CHIANTI abundance file. This is used for 
               calculating the proton to electron ratio. Default is 
               !abund_file.

       IONEQ_FILE  The name of a CHIANTI ion balance file. This is used for 
               calculating the proton to electron ratio and evaluating 
               the T_max of the ion. Default is !ioneq_file.

       RADTEMP  The blackbody radiation field temperature (default 
                6000 K).

       RPHOT    Distance from the centre of the star in stellar radius 
                units. I.e., RPHOT=1 corresponds to the star's surface. 
                (Default is infinity, i.e., no photoexcitation.)

 KEYWORDS:

	CHOOSE:	Allow ion balance calculations to be selected manually 
		(see choose_ioneq.pro routine).

 OPTIONAL OUTPUTS:

	OUTSTR:	A structure with the following tags

		.tmem	- the T_mem for the line(s)
		.dec	- total( de * c_lambda )
		.pidec	- 4 * pi / total( de * c_lambda )

	Only output when INDEX is specified.

 COMMON BLOCKS:

	None.

 CALLS:

	EMISS_CALC, CH_GET_FILE, READ_IONEQ

 HISTORY:

	Ver.1: PRY, 28-JUN-97.
	Ver.2: PRY, 7-OCT-97. Added TEMPI and GOFT, for plotting.
	Ver.3: PRY, 31-JUL-98. Added PATH.
	Ver.4: PRY, 6-APR-99. Added INDEX, OUTSTR. Removed TEMPI and GOFT 
		(these can be got from the g_of_t routine).
       Ver.5: PRY, 9-Dec-01. Modified for v.4 of CHIANTI.

       V.6, 21-May-2002, Giulio Del Zanna (GDZ) 
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

       V.7, 06-Aug-02 GDZ
              Changed the use of CHIANTI system variables. 
       

 VERSION     :   7, 06-Aug-02 

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	READ_ABUND

 PURPOSE:

	to read CHIANTI abundance files

 CATEGORY:

	science.

 CALLING SEQUENCE:

       READ_ABUND,File,Abundance,Reference


 INPUTS:

	File:  the name (string) of the file containing the abundance values
                (relative to hydrogen) usually of the form 
                 '!xuvtop/abundance/*.abund'


	

 OUTPUTS:

	Abundance:  an array of abuncance values
       Reference:  a string containing the reference to the chosen set
                   of abundances in the scientific literature



 PROCEDURE:

	You can describe the foobar superfloatation method being used here.

 EXAMPLE:

             > read_abund,'allen.abund',abundance,ref
               abundance(26) = abundance of iron relative to hydrogen
               quoted by C.W. Allen in Astrophysical Quantities

 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	March 1996:     Version 2.0

       V.   3, 21-May-2002, Giulio Del Zanna (GDZ) 
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

 VERSION     :   3, 21-May-2002 

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	READ_DEM

 PURPOSE:

	to read values the differential emission measure as a function 
       of temperature

 CATEGORY:

	science.

 CALLING SEQUENCE:

       READ_DEM, File, T, Dem, Ref


 INPUTS:

	File:  the name of the file containing the DEM values, usually in
               !xuvtop/dem/*.dem	


 OUTPUTS:

	T:  Log10 values of temperature (K)
       Dem:  Log10 values of the differential emission measure
       Ref:  the reference to the DEM values in the scientific literature


 OPTIONAL OUTPUTS:

	Describe optional outputs here.  If the routine doesn't have any, 
	just delete this section.



 EXAMPLE:

             > read_dem,!xuvtop+'/dem/active_region.dem',t,dem,ref

 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	March 1996:     Version 2.0

       V.   3, 21-May-2002, Giulio Del Zanna (GDZ) 
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

       Ver.4, 20-Nov-2002, Peter Young
           DEM values of -1 caused errors, so this has been corrected.

 VERSION     :   4, 20-Nov-2002 

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	READ_IONEQ

 PURPOSE:

	to read files containing the ionization equilibrium values

 CATEGORY:

	science.

 CALLING SEQUENCE:

       READ_IONEQ, File, T, Ioneq, Ref


 INPUTS:

	File:	for example, !xuvtop+'/ioneq/arnaud_rothenflug.ioneq'

 OPTIONAL INPUTS:

	None:
	

 OUTPUTS:

	T:  array of log10 temperatures
       Ioneq:  3-d array (T,element,ion) 
               of the fractional abundance of the ion in
              ionization equilibrium.
       Ref:  reference in the scientific literature


 EXAMPLE:

             > read_ioneq,!xuvtop+'/ioneq/arnaud_rothenflug.ioneq'
             > help,t,ioneq
             > T               FLOAT     = Array(41)
             > IONEQ           FLOAT     = Array(41, 28, 29)
             > print, minmax(t)
             >  4.00000      8.00000
             > print,t(20)
             >  6.0000
             > print,ioneq(20,25,9)
             >   0.269                  = fractional abundance of  Fe X in
                                          ionization equilibrium 

 MODIFICATION HISTORY:
 	Written by:	Ken Dere (KPD)
	March 1996:     Version 2.0
       March 1999:     KPD to read both number of temperature and number 
                       of elements

       25-Oct-2000     V. 4, Giulio Del Zanna (GDZ).
                       Corrected to interpret the '-1' as a reference only
                       if within the first 3 columns

       V.  5, 21-May-2002, Giulio Del Zanna (GDZ) 
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

       v.6, 25-Oct-2004, Peter Young
            modified format statement so that it will read any number of
            temperatures.

       V 7, 25-May-2005, GDZ 
                  corrected routine header.

 VERSION     :   7, 25-May-2005

 PROJECT:  CHIANTI

       http://wwwsolar.nrl.navy.mil/chianti.html

       CHIANTI is an atomic database package for the calculation of
       continuum and emission line spectra from astrophysical plasmas. It is a 
       collaborative project involving the Naval Research Laboratory
       (Washington DC, USA), the Arcetri Observatory (Firenze, Italy), and the
       Cambridge University (United Kingdom).


 NAME:
       CH_READ_FITS

 PURPOSE:

       Read  standard CHIANTI FITS binary table data containing the output from
       CH_SYNTHETIC and output a TRANSITIONS structure.

 CALLING SEQUENCE:

       CH_READ_FITS,  Filename, TRANSITIONS

 INPUTS:

       Filename = String containing the name of the CHIANTI FITS file written
       by CH_WRITE_FITS.

 OUTPUTS:

       TRANSITIONS = Structure to be written.

 OPTIONAL INPUTS: none

 KEYWORDS: none


 NOTES:
 

 CALLS:
        MRDFITS, ADD_TAG
	
 COMMON BLOCKS: none.

 RESTRICTIONS:

       (3)     The input FITS file must have been written by  CH_WRITE_FITS

 PREV. HIST. :


 EXAMPLE:

         ch_read_fits,  'file.fits', transitions 

 WRITTEN     : 

       Ver.1, 8-Apr-02 Giulio Del Zanna (GDZ)
       V.2 GDZ 31 May 2002 added more checks.

 MODIfICATION HISTORY:

 VERSION     : 2, 31 May 2002 

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
       CH_WRITE_FITS

 PURPOSE:
       Write  standard FITS binary table data from CHIANTI input  structure.

 CALLING SEQUENCE:
       CH_WRITE_FITS, Input, Filename

 INPUTS:

       Input = Structure to be written to FITS file.


 OUTPUTS:


       Filename = String containing the name of the file to be written.
                CH_WRITE_FITS creates two binary table extension in a single
                FITS file. The second one is appended as a new extension.

 OPTIONAL INPUTS:  Header COMMENTS.

 KEYWORDS: 
           head1, head2
          Additional  COMMENTS to be added at the bottom of the two binary tables.


 NOTES:
 
       Any existing FITS file can be over-written or not.
       Use CH_READ_FITS  to convert the FITS file back into a structure. 

 CALLS:

	FXPAR(), FXADDPAR, IS_IEEE_BIG(), HOST_TO_IEEE, DIALOG_MESSAGE

 COMMON BLOCKS: none.

 RESTRICTIONS:
       (1)     Limited to 127 columns in tables by IDL structure limits.
       (2)     String columns with all columns of zero length crash the
               program
       (3)     The input structure has to be of the type TRANSITIONS.

 PREV. HIST. :

       The subroutines in this procedure are extracted without modifications from
       the MWRFITS.PRO routine, written by T. McGlynn Version 0.95 2000-11-06
       and present in the ASTRON library (in SolarSoft under /gen/idl_libs/astron/).

 EXAMPLE:

         ch_write_fits, transitions , 'test.fits'

 WRITTEN     : 
       Ver.1, 22-May-02 Giulio Del Zanna (GDZ)


 MODIfICATION HISTORY:

 VERSION     : 1, 22-May-02, GDZ

 NAME

     WHICH_LINE

 PROJECT

     CHIANTI

 PURPOSE:

     Upon given an ion name and wavelength, this routine prints out a list
     of possible line IDs for the wavelength. Wavelengths within 1% of the
     input wavelength are searched for.

 INPUTS

     IONNAME  Name of an ion in the CHIANTI format. E.g., 'fe_13' for Fe XIII.

     WVL      A wavelength in angstroms.

 OUTPUTS (to screen)

     Prints a list of atomic transitions and wavelengths for lines close to
     the input wavelength. A '*' is placed next to the closest wavelength
     match.

 KEYWORDS

     NARROW   Narrows the search range to 0.02% of the specified wavelength.

 EXAMPLE

     IDL> which_line,'o_6',1032
     Wavelength   i   j Lower level           Upper level             A-value
       1037.615   1   2 1s2.2s 2S1/2        - 1s2.2p 2P1/2          4.21e+008
       1031.914   1   3 1s2.2s 2S1/2        - 1s2.2p 2P3/2          4.28e+008

 CALLS

     CONVERTNAME, ZION2FILENAME, READ_WGFA2, READ_ELVLC

 HISTORY

     Ver.1, 22-Jun-2004, Peter Young

 Project     : CHIANTI

       CHIANTI is an atomic database package for the calculation of
       continuum and emission line spectra from astrophysical plasmas. It is a 
       collaborative project involving the Naval Research Laboratory
       (Washington DC, USA), the Arcetri Observatory (Firenze, Italy), and the
       Cambridge University (United Kingdom).
 
                   
 Name        : USE_CHIANTI
               
 Purpose     : Sets up system variables for use of CHIANTI routines
               
 Explanation : The  CHIANTI software uses system variables
               that have to be defined. This routine is called by the 
               CHIANTI routines if these system variables are not defined.

               ** If one is using the solar-soft package, these should 
               already be defined*****.

               ** If the CHIANTI package is used as stand-alone, then 
               this routine can be used for the setup with e.g.:

               use_chianti,'/home/data/chianti/'

               if /home/data/chianti/ points to the actual place where 
               the CHIANTI top directory is.

               
 Use         : IDL> use_chianti, '/home/data/chianti/', $
                                 [ioneq= , abund=]
    
 Inputs      : None
               
 Opt. Inputs : The full pathname of the CHIANTI top directory.
               
 Outputs     : None
               
 Opt. Outputs: None
               
 Keywords    : IONEQ  - to define the default ionization eq. file to be used.
               ABUND  -  to define the default abundance file to be used.

 Calls       : None

 Common      : None
               
 Restrictions: None
               
 Side effects: None
               
 Category    : 
               
 Prev. Hist. : Based on use_dere_chianti, written by C D Pike, RAL

 Written     : Giulio Del Zanna (GDZ)  DAMTP  (University of Cambridge, UK) 
               
 Modified    : Version 1, GDZ 10-Oct-2000
               Version 2, GDZ 10-Jan-2001
               added the definition of the !abund_file

               V. 3, GDZ, 2-May-2002 Modified substantially, adding a new
               system variable.

               V.4, 10-July-2002 GDZ
                 Removed the definition of !chianti_top, upon request.

               V.5, 25-July-2002, GDZ 
                Fixed a problem with IDL versions earlier than 5.3 (the routine
                would not compile). ALso, introduced the use of concat_dir for
                cross-platform compatibility.
                    
               V.6, 06-Aug-02 GDZ
                 Changed the use of CHIANTI system variables. Added comments on
                 the which CHIANTI version is used.
               V.7 12-Aug-02 GDZ Changed default abundance file. Removed '***'
               V.8, GDZ 13-Feb-2003
                   Changed default ioneq  file, to include ALL the elements.

               V.9,  12-Aug-2005, GDZ 
                   Changed default ioneq file from mazzotta_etal_ext to 
                   mazzotta_etal_9.ioneq where ion fractions have been extended
                   up to 10^9 K. This is useful to avoid steps in the
                   emissivities at high-temperatures.


 Version     : V.9,  12-Aug-2005

G  List of all CHIANTI routines with description and headers (alphabetical order)

• ASCII_WVL_DEM
  create an ascii file of predicted spectral line intensities and wavelengths corresponding to a selected abundance and differential emission measure (DEM).
  
• BB_RAD_LOSS
  calculates energy loss rate by line (bound-bound) radiation
  
• CALC_DMM_DR
  Calculates CHIANTI density sensitive line ratios. Explanation :
  
• CALC_DMM_TR
  Calculates CHIANTI temperature sensitive line ratios. Explanation :
  
• CHIANTI_DEM
  Calculates the Differential Emission Measure DEM(T) using Constant pressure or density can be used.
  
• CHIANTI_NE
  Calculate and plot CHIANTI density sensitive line ratios. Explanation : CHIANTI_NE (density ratios) calculates and plots density sensitive line ratios based on the CHIANTI atomic database of Dere et. al.
  
• CHIANTI_TE
  Calculate and plot CHIANTI temperature sensitive line ratios. Explanation : CHIANTI_TE (temperature ratios) calculates and plots temp. sensitive line ratios based on the CHIANTI atomic database of Dere et. al.
  
• CH_CHECK_STR
  To check that an input structure is of the right type
  
• CH_DRAWBOX
  Allows the selection of a sub-region within a plot using a "rubberband box".
  
• CH_GET_FILE
  to select a file from either a selected directory or the working directory, having an extension.
  
• CH_LINE_LIST
  Create a latex or an ascii file of predicted spectral line intensities and wavelengths corresponding to selected parameters, as calculated by CH_SYNTHETIC. Needs as input the line intensity structure calculated by CH_SYNTHETIC (default) or the SPECTRUM structure output of MAKE_CHIANTI_SPEC.
  
• CH_READ_FITS
  Read standard CHIANTI FITS binary table data containing the output from CH_SYNTHETIC and output a TRANSITIONS structure.
  
• CH_SS
  Widget-based multi-purpose routine to calculate CHIANTI line intensities and continua, to create a synthetic spectrum, to make tables of lines, etc.
  
• CH_SYNTHETIC
  to calculate CHIANTI line intensities or G(T) and output an IDL structure.
  
• CH_WRITE_FITS
  Write standard FITS binary table data from CHIANTI input structure.
  
• CH_XMENU_SEL
  Allow user to select a set of items from a list. Widget equivalent of WMENU_SEL
  
• CI_REC_INTERP
  For including ionization and recombination into the level balance, it's necessary to interpolate the data stored in the CHIANTI files and, in addition, perform extrapolation to lower or higher temperatures.
  
• CONF2N
  Extract the highest principal quantum number from the configuration
  
• CONVERTNAME
  numerical values (note c_2 is C II or C^+1 in spectroscopic or atomic notation)
  
• CONVERT_TERMS
  to convert the transition information into readable formats.
  
• CONVERT_TERMS_ALL
  to convert level information into readable formats for all the levels of an ion.
  
• CORRECT_POPS
  Corrects CHIANTI level populations with the ionization and recombination rate coefficients
  
• DEM_FIT
  Calculates the Differential Emission Measure DEM(T) using
  
• DENSITY_RATIOS
  to calculate line intensity ratios as a function of electron density
  
• DENS_PLOTTER
  A widget-based routine to allow the analysis of density sensitive ratios. **** See RATIO_PLOTTER for details. *****
  
• DESCALE_ALL
  
  
• DESCALE_UPS
  convert from Burgess-Tully scaling spline fits to Upsilons
  
• EMISS_CALC
  To compute the emissivities of all lines of a specified ion over given ranges of temperature and density.
  
• EMISS_SELECT
  
  
• FB_RAD_LOSS
  Returns the value of zeta_0 (the number of vacancies in the ion given by IZ and ION). See Sect. 2.2 of Mewe et al. (1986, A&AS 65, 511).
  
• FF_RAD_LOSS
  Calculate the free-free radiative energy losses losses. Uses the free-free integrated gaunt factor calculations of Sutherland, 1998, MNRAS, 300, 321
  
• FINDEX
  Compute "floating point index" into a table using binary search. The resulting output may be used with INTERPOLATE.
  
• FREEBOUND
  Calculates the free-bound (radiative recombination) continuum.
  
• FREEBOUND_ION
  Calculates the free-bound (radiative recombination) continuum from a single ion. Note that the output does not contain the ion fraction, element abundance or differential emission measure term.
  
• FREEFREE
  This routine computes the free-free continuum (bremsstrahlung) using the fitting formulae of Itoh et al. (ApJS 128, 125, 2000) and Sutherland (MNRAS 300, 321, 1998).
  
• GET_ATOMIC_WEIGHT
  to produce an atomic weight.
  
• GET_CONTRIBUTIONS
  calculates the contribution functions G(T) at constant database, corresponding to a given set of observed lines.
  
• GET_IEQ
  For a specified ion (IZ, ION) and set of temperatures (TEMP) this routine takes the ion fraction values tabulated in one of the CHIANTI .IONEQ files, interpolates and extracts the values of the ion fraction at the input temperatures.
  
• GOFNT
  calculate G(n,T) function (line intensity per unit emission measure)
  
• G_OF_T
  To compute DE * F(T) * n_j * A_ji / N_e for selected emission lines. Option to also multiply by abundance.
  
• HASTOGRAM
  
  
• INTEGRAL_CALC
  To compute the atomic data integral for use in column or volume emission measure work.
  
• ION2FILENAME
  provide their complete file name (with out suffix)
  
• ION2SPECTROSCOPIC
  provide identification string
  
• ION_FRAC_INTERP
  Performs interpolation of an ion fraction array (such as contained in the CHIANTI .ioneq files) to yield ion fractions at temperatures TEMP.
  
• ION_INTERP
  
  
• ISOTHERMAL
  Computes spectra from isothermal plasmas. A number of isothermal plasmas can be included. Note that this routine has a number of unique features that distinguish it from the other CHIANTI synthetic spectra routines. See the Programming Notes section.
  
• ITOH
  Calculates the relativistic free-free continuum using the fitting formula of Itoh et al. (ApJS 128, 125, 2000).
  
• KARZAS_XS
  Outputs the photoionization cross-section at the wavelengths WVL for ionization of an N,L electron with ionization energy IONIZ_EN, calculated using the Karzas & Latter (ApJS 6, 167, 1961) formulation. The bound-free gaunt factor is derived from the tables of Karzas & Latter.
  
• LANDSCAPE
  :
  
• LATEX_WVL_DEM
  create a latex file of predicted spectral line intensities and wavelengths corresponding to a selected abundance and differential emission measure (DEM)
  
• MAKE_CHIANTI_SPEC
  To create a CHIANTI synthetic spectrum
  
• MAKE_ION_LIST
  Reads masters ions list and interprets. Explanation : Reads the CHIANTI master ion list and returns the list of available elements and ions in suitable arrays.
  
• MATRIX_SOLVER
  Takes the matrices for the various atomic processes employed in CHIANTI and returns the level populations.
  
• MAX_TEMP
  Calculates temperature at max ionisation ratio for an ion Explanation :
  
• MID2BOUND
  
  
• PLOT_CHIANTI_NE
  Plots a density sensitive ration saved from CHIANTI_NE Explanation : The routine CHIANTI_NE allows the calculated ratio to be saved in an IDL save file. This routine retrieves and plots the ratio.
  
• PLOT_CHIANTI_TE
  Plots a temperature sensitive ratio saved from CHIANTI_TE Explanation : The routine CHIANTI_TE allows the calculated ratio to be saved in an IDL save file. This routine retrieves and plots the ratio.
  
• PLOT_DEM
  To plot differential emission measure (DEM) values
  
• PLOT_DMM_DR_FIG
  Plots line intensities in DMM_DR Explanation : Internal routine used by CHIANTI_NE for plotting individual line intensities.
  
• PLOT_DMM_TR_FIG
  Plots line intensities in DMM_TR Explanation : Internal routine used by CHIANTI_TE for plotting individual line intensities.
  
• PLOT_IONEQ
  Plots the ionisation equilibrium values for an element. Explanation :
  
• PLOT_POPULATIONS
  electron density for a specific temperature
  
• POP_PLOT
  To compute n_j A_ji / N_e for a selected transition(s) and plot it against N_e. If it is insensitive to N_e, then the line(s) is suitable for emission measure analysis.
  
• POP_PROCESSES
  Outputs to the screen the contributions of the different physical processes to the population of the specified level within the ion.
  
• POP_SOLVER
  To solve the level balance equations for Chianti ions.
  
• PRINT2D_PLOT
  this routine optionally changes the ranges of a 1D plot and print the plot to a landscape postscript file.
  
• PROTON_DENS
  Calculates the ratio of the proton density to electron density using abundance and ion balance files.
  
• R2W
  Converts a distance above a star into a dilution factor.
  
• RAD_LOSS
  Calculates energy loss rate by free-free (ff), radiative recombination (fb) and by line (bound-bound) radiation.
  
• RATE_COEFF
  Returns the electron rate coefficient in units of cm^3 s^-1. Either the entire excitation/de-excitation array for the specified ion or, if the TRANS= keyword is used, the excitation rate for the specified transition.
  
• RATIO_PLOTTER[1]
  temperature sensitive ratios.
  
• RATIO_PLOTTER[2]
  
  
• READ_ABUND
  to read CHIANTI abundance files
  
• READ_DEM
  to read values the differential emission measure as a function of temperature
  
• READ_ELVLC
  to read files containing observed and theoretical energy levels
  
• READ_ELVLC_DIRECT
  to read files containing observed energy levels does not reformat some variables like READ_ELVL
  
• READ_FBLVL
  To read files containing observed free-bound energy levels
  
• READ_GFFGU
  Read gffgu.dat file containing free-free gaunt factors of R. S. Sutherland, 1998, MNRAS, 300, 321 note: the file available from the web site are mislabelled
  
• READ_GFFINT
  Read gffint file containing integrated free-free gaunt factors of R. S. Sutherland, 1998, MNRAS, 300, 321
  
• READ_IONEQ
  to read files containing the ionization equilibrium values
  
• READ_IP
  to read values of ionization potentials
  
• READ_KLGFB
  to read CHIANTI files file containing the free-bound gaunt factors for n=1-6 from Karzas and Latter, 1961, ApJSS, 6, 167
  
• READ_MASTERLIST
  read the masterlist.ions types of file and output a list of ions
  
• READ_SPLUPS
  to read file containing spline fits to the Burgess-Tully scaled collision strengths
  
• READ_WGFA
  :
  
• READ_WGFA2
  read radiative data files a modified version of read_wgfa needed to take account of two types of transitions between the same 2 levels: for example, the M1 and the 2 photon E1 transition 1s-2s in hydrogenic ions
  
• REBINW
  
  
• SETUP_ELEMENTS
  read in ionization equilibrium and abundances not for general user use
  
• SETUP_ION
  Several of the CHIANTI routines require the atomic data for ions to be read into common blocks, and so this routine performs this task for individual ions.
  
• SHOW_POPS
  To display populations of significant levels in a CHIANTI ion model
  
• SPECTROSCOPIC2ION
  
  
• SUTHERLAND
  Calculate the free-free continuum from an hot, low density plasma
  
• SYNTHETIC
  calculates a synthetic spectrum
  
• SYNTHETIC_PLOT
  to plot out synthetic spectra calculated with Synthetic and interactively identify spectral lines
  
• TEMPERATURE_RATIOS
  calculate and display temperature sensitivity of line intensity ratios
  
• TEMP_PLOTTER
  A widget-based routine to allow the analysis of temperature sensitive ratios. **** See RATIO_PLOTTER for details. *****
  
• TWO_PHOTON
  Calculate the 2 photon continuum from a hot, low density plasma.
  
• USE_CHIANTI
  Sets up system variables for use of CHIANTI routines Explanation : The CHIANTI software uses system variables that have to be defined. This routine is called by the CHIANTI routines if these system variables are not defined.
  
• VERNER_XS
  Reads the Verner & Yakovlev (A&AS 109, 125, 1995) photoionization cross-section data and generates the values of the cross-section at the wavelengths WVL
  
• W2R
  Converts a dilution factor into a distance above a star.
  
• WHICH_LINE
  Upon given an ion name and wavelength, this routine prints out a list of possible line IDs for the wavelength. Wavelengths within 1% of the input wavelength are searched for.
  
• Z2ELEMENT
  
  
• ZION2FILENAME
  help locate CHIANTI database files
  
• ZION2SPECTROSCOPIC
  
  
• [1]
  Generates standard fonts for CHIANTI GUIs suitable for both Unix and Windows operating systems.
  
• [2]
  Calculate the total radiative losses of a plasma due to the free-bound (radiative recombination) continuum.
  

Routine Descriptions

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	ASCII_WVL_DEM

 PURPOSE:

	create an ascii file of predicted spectral line intensities and
       wavelengths corresponding to a selected abundance and differential
       emission measure (DEM).  


 PROCEDURE:

                 Calculations are done assuming either constant density or
                 constant pressure. See CH_SYNTHETIC for details.


 CALLING SEQUENCE:

       ASCII_WVL_DEM, Wmin, Wmax, Pressure= , [density= ], $ 
              [outfile= , mini= , sngl_ion=, /photons, /all, /masterlist], $
              [/noprot, radtemp=, rphot=]


 INPUTS:

	Wmin:   lower limit of the wavelength range of interest (Angstroms)	
               if kev keyword set, then wmin is in kev	
	Wmax:   upper limit of the wavelength range of interest (Angstroms)
               if kev keyword set, then wmax is in kev	

       Pressure:  pressure in emitting region (cm^-3 K), or 
       Density:   density in emitting region (cm^-3).


 OPTIONAL INPUTS:

       OUTFILE: the name of the output ascii file to be written.
	
	MINI:	Minimum intensity for a line to be included in the output.

	SNGL_ION:  specifies  a single ion (e.g. SNGL_ION='Fe_10' to include
                 only Fe X lines) or an array (e.g. SNGL_ION=['Fe_10','Fe_11']
                 to include only Fe X and Fe XI lines) of ions to be used
                 instead of the complete set of ions specified in
                 !xuvtop/masterlist/masterlist.ions 

       MASTERLIST: string of a specific masterlist file (full path). 
                   If defined as a keyword (i.e. MASTERLIST=1 or /MASTERLIST)
                   then a widget allows the user to select a  user-defined
                   masterlist file. Shortcut for SNGL_ION.   


 OUTPUTS:

	an ascii file:   linelist.txt  in the working directory by default

 OPTIONAL OUTPUTS:


 KEYWORD PARAMETERS:

	MINI:	Minimum intensity for a line to be included in the output

	SNGL_ION:  specifies  a single ion (e.g. SNGL_ION='Fe_10' to include
                 only Fe X lines) or an array (e.g. SNGL_ION=['Fe_10','Fe_11']
                 to include only Fe X and Fe XI lines) of ions to be used
                 instead of the complete set of ions specified in
                 !xuvtop/masterlist/masterlist.ions 

       MASTERLIST: string of a specific masterlist file (full path). 
                   If defined as a keyword (i.e. MASTERLIST=1 or /MASTERLIST)
                   then a widget allows the user to select a  user-defined
                   masterlist file. Shortcut for SNGL_ION.   


       PHOTONS:  units will be in photons rather than ergs

       KEV:  wavelengths will be given in kev rather than Angstroms

       ALL:  if set, then all lines are included.  This means that lines 
             for which
             only an approximate wavelength is known (only theoretical energy
             levels are known) are included.


       OUTFILE:  the name of the output ascii file to be written. By 
                default a
                file 'linelist.txt' in the user's working  directory will be
                created. 

       NOPROT  If set, then the default setting will be NOT to use 
               proton rates. This can be changed within the routine.

	RADTEMP	Specify background radiation temperature (default: 6000 K)

	RPHOT   Distance from the centre of the star in stellar radius units.
               I.e., RPHOT=1 corresponds to the star's surface. (Default is
               infinity, i.e., no photoexcitation.)

 CALLS:
       
       CH_SYNTHETIC, CH_LINE_LIST


 COMMON BLOCKS: None

 RESTRICTIONS:

 SIDE EFFECTS:


 EXAMPLE:

            IDL> ascii_wvl_dem,400.,800., out='linelist',$ 
               pressure=1.e+15,mini=1.,sngl_ion='o_4'

 CATEGORY:

	spectral synthesis.

 WRITTEN     : 

       Version 1, 8-Nov-01, Giulio Del Zanna (GDZ). 

       Compared to the previous ASCII_WVL_DEM, these are the main changes:

       1-Rewritten as a wrapper routine using the new procedures.
       2-Now the PRESSURE value is a keyword.
       3-The calculations can be done at constant DENSITY.
       4-Energies (keV) can be output instead of wavelengths in Angstroms    
       5-MASTERLIST can now be used both as an input string or as a keyword.

 MODIFICATION HISTORY:

      18-Nov-01, Peter Young
         Added /noprot, rphot and radtemp keywords
       V. 2, 22-May-2002 GDZ.  Removed const_net definitions.

 VERSION     : 2, 22-May-2002

 PROJECT:  CHIANTI

 NAME:
	bb_rad_loss

 PURPOSE:

       calculates energy loss rate by line (bound-bound) radiation

 CATEGORY:
	
	synthetic spectra

 CALLING SEQUENCE:

       BB_RAD_LOSS,Temperature,Loss_rate


 INPUTS:

	None:  the user will select various parameters such as the 
              choice of elemental abundances and ionization equilibria

  KEYWORDS:

       Pressure:  pressure in emitting region (cm^-3 K)
                  density=pressure/temperature(K)

       Density:   density (cm^-3), constant for all temperatures
                  if neither density or pressure is set, then a 
                  default constant density of 10^10 cm^-3 is used.

	Sngl_ion:  to calculate the loses spectrum for a single ion

       NOPROT    Switches off inclusion of proton rates.

       RADTEMP   The blackbody radiation field temperature (default 
                 6000 K).

       RPHOT     Distance from the centre of the star in stellar radius 
                 units. I.e., RPHOT=1 corresponds to the star's surface. 
                 (Default is infinity, i.e., no photoexcitation.)

 OUTPUTS:

       Temperature:  array of temperatures (K)
       Loss_rate:  energy loss rate in erg cm^3 s^-1


 PROCEDURE:


  if keyword pressure is set then calculations performed at constant pressure
  if keyword density is set then calculations performed at constant density
  otherwise, density is set to 1.e+10
  
  pressure = density * temperature  (cm^-3 K)


	the user will be asked to select an abundance file. 


 COMMON BLOCKS:

	ELVLC, WGFA, UPSILON, RADIATIVE, PROTON, ELEMENTS, IONREC

 CALLS

       READ_MASTERLIST, 
       SETUP_ELEMENTS, POP_SOLVER, CONVERTNAME, R2W, PROTON_DENS,
       ZION2SPECTROSCOPIC, ZION2FILENAME, SETUP_ION

 EXAMPLE:

       > bb_rad_loss,t,r


 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	January 1999:  version 1, adopted from synthetic.pro
       14-Jul-2000     Peter Young, now calls pop_solver

       Ver.2, 9-Dec-2001, Peter Young
               Modified for v.4 of CHIANTI.

       V.3, 4-Oct-2003, GDZ
                  modified the input to POP_SOLVER, now it is dealt with an
                  input structure. Also shorten the whole procedure, by calling
                  other procedures.

       V.4, 5-Apr-2005, EL
                  modified the input to POP_SOLVER in order to add ion/rec
                  in the calculation of level populations. All the rest
                  is unchanged.

       V 5, 25-May-2005, GDZ 
                  corrected routine header.


 VERSION     :   5, 25-May-2005, GDZ 

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 

                   
 Name        : CALC_DMM_DR
               
 Purpose     : Calculates CHIANTI density sensitive line ratios.
               
 Explanation : 
               
 Use         : Called from DMM_NE
    
 Inputs      :  ciz  - element number
                cion - ion number
                denmin, denmax - log density range
                mess_win - message widget ID for DMM_NE use.
               
 Opt. Inputs :  None
               
 Outputs     :  None
               
 Opt. Outputs:  None
               
 Keywords    :  Temperature - if set use this temperature rather than 
                              temp at max of ioneq.

 Calls       :  EMISS_CALC

 Common      :
               
 Restrictions:  None
               
 Side effects:  None
               
 Category    :  Spectral
               
 Prev. Hist. :  Based on density_ratios by K Dere.

 Written     :  C D Pike, RAL, 22-Jan-96
               
 Modified    :  Send warning message to widget.  CDP, 27-Jan-96
                Update generally.  CDP, 7-Jun-97
                Corrected typo in reading elvlc file.  CDP, 14-Jul-97
                Added minimum line ratio factor.  CDP, 17-Jul-97
                Added multiple wavelength ranges. CDP, 18-Jul-97
                Fix typo for XXII stage.          CDP, 05-Mar-98
                Update list of elements.          CDP, 18-Jun-99
                v. 9. Correct hiccup in above.          CDP, 13-Jul-99

                Update for compatibility with CHIANTI v.3. Replaced populate
                with pop_solver. Left out 'dielectronic' lines. ouput
                temperature. plus various small additions.
                Now ratios are calculated with  0.1 increment in log Ne
                Giulio Del Zanna (GDZ) 10-Oct-2000 

                Ver.11, 7-Dec-01, Peter Young (PRY)
                modified for v.4 of CHIANTI 

                Ver. 12, 1-May-02, GDZ
                Fixed a bug:  Added nlist = 0 when no lines are present. 
                V. 13, 21-May-2002, GDZ 
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

                V.14, 06-Aug-02 GDZ
                   Changed the use of CHIANTI system variables. 

               V.15, 16-Sep-2004, GDZ
                    added /NO_DE in call to emiss_calc as chianti_te expects
                    emissivities in photon units
                 
 Version     :  Version 15, 16-Sep-2004

 Project     : SOHO - CDS     
                   
 Name        : CALC_DMM_TR
               
 Purpose     : Calculates CHIANTI temperature sensitive line ratios.
               
 Explanation : 
               
 Use         : Called from DMM_TE
    
 Inputs      :  ciz  - element number
                cion - ion number
                wmin, wmax - wavelength range
                temmin, temmax - log temperature range
                mess_win - message widget ID for DMM_TE use.
               
 Opt. Inputs :  None
               
 Outputs     :  None
               
 Opt. Outputs:  None
               
 Keywords    :  None

 Calls       :  EMISS_CALC

 Common      :
               
 Restrictions:  None
               
 Side effects:  None
               
 Category    :  Spectral
               
 Prev. Hist. :  Based on temperature_ratios by K Dere.

 Written     :  C D Pike, RAL, 22-Jan-96,
 Modified    :  H E Mason, 03-Oct-96 (density to temperature)
               
 Modified    :  Send warning message to widget.  CDP, 27-Jan-96
                Update list of elements and cut call to 
                       read_elvl.                CDP, 18-Jun-99
                V.3. Fix hiccupp in above.            CDP, 13-Jul-99

                V.4. Rewritten completely, adding possibility to pass on the
                density at which the intensities are calculated, and making
                this routine compatible ith CHIANTI v.3.
                Giulio Del Zanna (DAMTP), 10 Oct-2000

                Ver.5, 7-Dec-2001, Peter Young
                Modified for v.4 of CHIANTI.

                Ver. 6, 1-May-02, GDZ
                Fixed a bug:  Added nlist = 0 when no lines are present. 

               V.7, 16-Sep-2004, Peter Young
                    added /NO_DE in call to emiss_calc as chianti_te expects
                    emissivities in photon units

 Version     :  Version 7, 16-Sep-04

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 

                   
 Name        : CHIANTI_DEM
     		          
 Purpose     : Calculates the Differential Emission Measure DEM(T) using 
		the CHIANTI database, from a given set of observed lines.
		Constant pressure or density can be used.

 Category    : diagnostic analysis
               
 Explanation : This routine has several options, all in the form of keywords.
 		First, the input file with the observed fluxes is read.
		THE FIRST TIME YOU USE THIS ROUTINE
		you'll have to do the calculation of the contribution
		functions G(T), so the routine GET_CONTRIBUTIONS will come 
		into play. You'll have to specify the value of the 
		pressure or density, and  you'll be asked to select an  
		ionization equilibrium file and an abundance file.
		GET_CONTRIBUTIONS searches the CHIANTI database (ion per ion) 
		for all the theoretical lines corresponding to the observed 
		lines, i.e. that lie in a OBS_WVL(i) +/- DELTA_LAMBDA_OBS(i) 
		interval centered on the observed wavelength OBS_WVL(i).
		The routine calculates the C(T) values (G(T)=Ab(element)*C(T))
		for the temperature interval log(T)= 4.0 - 8.0  
		with steps of log(T) = 0.1 .
		You can either select a constant pressure OR a constant 
		density for all the lines; if you select a constant pressure,
               for each ion the contribution function is calculated at an 
               electron density N_e equal to the ratio of the pressure 
               and the temperature of maximum ionization fraction:  
               C=C( T, N_e= P/T_ion )  
               The C(T) values are stored by GET_CONTRIBUTIONS in the output 
		file OUTPUT.CONTRIBUTIONS that can be used later to calculate
		the DEM, changing various parameters,
		without having to start again and read the CHIANTI database,
		which can take long time.

		In the case no theoretical lines corresponding to an observed
		line are found, the routine writes the wavelength of the line
		(to be excluded from the fit) in the array
		EXCLU_OBS_WVL_NO_TEO. The lines with no theoretical 
		counterparts are then automatically  excluded from the fit by 
	 	CHIANTI_DEM. You might consider the possibility to start again
		incrementing the DELTA_LAMBDA_OBS, to see if there are 
		theoretical lines in the vicinity.
		Note: if you want to exclude some of the observed lines from 
		the fit, you just have to use the keyword EXCLUDE_OBS_WVL, 
		BUT  GET_CONTRIBUTIONS will store anyway the results (if any)
		in the C(T) file.

		After having excluded the lines in EXCLUDE_OBS_WVL, 
		any *.abund file present in the CHIANTI database or in 
		the working directory can be selected, and eventually edited,
		if you like to change some abundances. 
		Then the $G(T)$ are calculated, multiplying each theoretical
		line by the abundance factor. Then the
		theoretical lines contributing to each blend are sorted by
		intensity and then their G(T) can be plotted if the keyword
		PLOT_GT is activated. It is recommended to do this the first 
		time, to check if there are some observed lines terribly 
		blended with lines of other elements, in which case it is
		better to exclude them with a second run (if you are not 
		sure about the abundances).
		Then the G(T) for each blend are summed and plotted.
		Then  the fit starts calling DEM_FIT. 
		A series of parameters can change the 
		result (DEM), especially the number and position of the mesh
		points of the spline that represents the DEM. The keyword
		MESH_POINTS serves for this purpose. 
		The other keywords that control the fit are N_ITER, DCHISQ_M.
   		At the end of the fit, the files OUTPUT.DEM and OUTPUT.GENERAL
		are created.



 Use         : IDL>chianti_dem,output='serts89',file_input='serts89.obs',$
				pressure=3.e15


 Examples    : 
		Assume you have a file input 'serts89.obs' like this:
		
		243.031   491.    97.    0.1  He II
		256.323   1580.   186.   0.1  He II b
		315.024   253.    31.    0.1  Mg VIII
		335.401   10400.  1650.  0.1  Fe XVI
		319.839   113.    14.    0.1  Si VIII
		356.027   218.    25.    0.1  Si X 
		
		IDL>chianti_dem,output='serts89',file_input='serts89.obs',$
		   pressure=3.e15,cut_gt=1e-30,/plot_gt

		After having selected the  ionization file,
		the C(T) (with MAX(C(T)) gt 1e-30)  are stored in the file
		'serts89.contributions'. Then select one of the abundance 
		files. 
		Have a look at the plots of the  G(T), and annotate
		if there is a line you want to exclude, let's say the second.
		Have a look at the DEM obtained ('serts89.dem') and at 
		the details contained in the file 'serts89.general'. 
		Maybe there is another line you want to exclude, let's say 
		the last one. Maybe you want to change the mesh points, too.
		So run
		IDL>chianti_dem,output='serts89_2',file_input='serts89.obs',$
		file_gt='serts89.contributions',$
		exclude_obs_wvl=[243.031,356.027 ],$
		mesh_points= [4.5,5.,5.5,6.2,7.5]
		
		The files 'serts89_2.dem' and 'serts89_2.general' will be
		created. They have the essential information about what you 
		did.

    
 Inputs      : various, all in form of keywords. The required ones are 
		OUTPUT and FILE_GT (or  PRESSURE/DENSITY)
               
               
 Opt. Inputs : various... see the software note.
               
 Outputs     : OUTPUT.CONTRIBUTIONS  
		Created only if the keyword FILE_GT is NOT set. 
		Is the file where all the contribution  functions G(T) are 
		stored. In the first two lines  the ionization equilibrium 
		file name, and the constant value of pressure or density 
		adopted are reported. Then for each line you have reported  
               the observed wavelength, the theoretical one, the element and
		ionization stage, then the C(T) values. At the end the 
		specification for each transition.

		OUTPUT.DEM
		Is the file where the log T and log DEM values are 
		written, with a format suitable 
		as input for the DMM_SS procedure,that calculates the 
		synthetic spectrum. At the end some info on how it was 
		calculated are printed.

		OUTPUT.GENERAL
		Is the file where general information is stored.
		The abundance file, the ionization equilibrium file and the
		constant value of pressure or density  used are reported. 
		Then there is one line for each
		observed line, with the provisional identification, the 
		observed wavelength, the observed flux, the theoretical one
		(corresponding to the DEM), the error on the flux,
		the square of the difference between the theoretical and the 
		observed fluxes divided by the error (this number should be 
		close to zero if the line is well reproduced), and finally
		the ratio of the theoretical flux versus the observed one 
		(which should be close to 1).
		After this line, there is one line per each theoretical line
		contributing to the blend, with the identification, the 
		theoretical wavelength, the configuration and terms, and the
		contribution to the total theoretical flux (in percentage) 
		of each line in the blend.

		OUTPUT.OUT
		This file , toghether with OUTPUT.DEM , 
		can be used to reproduce the results  using 
		user-written software. See the software notes.
		The ouput has this format: 
		format='(a20,1x, 1f10.3,1x, 3e10.3, 1x,  f4.2,1x,f6.3)'	
	
 Opt. Outputs:
		An abundance file with the modifications inserted.
	
		Postscript files of the G(T).
	
		A postscript file with the DEM (OUTPUT.DEM.PS)
		
               A postscript file with other plots too (OUTPUT_4PLOTS.PS)

 Keywords    : 


	ARCSEC: 
		optional. If set, it means that the intensities in the input
		file are per arcsec-2 .
		These intensities are then  converted to 
		 sterad-1 .

	CUT_GT:	
		optional. If set, only the those theoretical lines that
		have a MAX(C(T))  greater than the value set, are kept; 
		it is useful to set this value in order to reduce the number 
		of lines in the file where the C(T) are stored.;  
		if not set, a default value of 1e-30 is adopted.

	DCHISQ_M:
		optional. If not set, a default value of DCHISQ_MIN=1.e-5 
		is assumed. For each iteration, the CHISQ and it's variation 
		are calculated. As long as the iteration achieves an
		improvement in CHISQ greater than  DCHISQ_MIN , another 
		iteration will be performed.

	DEM_FILE:
		optional.If set (,/DEM_FILE) you have to choose a DEM file to 
		be used as a start, instead of the default constant value of 
		10.^22.
		You can either choose one of the files in the CHIANTI database
		or any you have in the working directory. 
		The values in the file are marked as crosses, the mesh points
		are marked with triangles.

	DENSITY : 
		the value of the density (Ne). Required if you do NOT have
		already the contribution  functions G(T). 

	EXCLUDE_OBS_WVL:
		optional.
		If set, you can  exclude some of the observed lines from 
               the fit. Note that even if you set this keyword and run 
		GET_CONTRIBUTIONS all the theoretical lines found corresponding
		to all the lines in the input file are written in the C(T) 
		file. It is only in the fit that the lines are excluded.

	FILE_GT:
		optional.
		If NOT set, the routine GET_CONTRIBUTIONS is called.
               If set, it has to specify the name of the file created by 
		GET_CONTRIBUTIONS, where all the contribution  functions G(T) 
               are stored. In the first two lines the ionization equilibrium 
		file name, and the value of the pressure or density 
               adopted is reported. Then for each line you have reported  
               the observed wavelength, the theoretical one, the element and
               ionization stage, then the C(T) values. At the end the 
               specification for each transition.

	FILE_INPUT:
		optional.
 		if set, you are not requested to select the observation file
		using a widget-type search.
		The input file  must contain 5 columns, unformatted:
		1)the observed wavelength (A)
		2)the observed flux in erg cm-2 s-1 st-1
		3)the corresponding error on the flux in erg cm-2 s-1 st-1
		4)half the width (A) of the range (centered on the observed 
		  wavelength) where you want to look for the corresponding 
		  theoretical lines. A value of HWHM or more would do.
		5)The identification, written as string (max 20 characters)

	MESH_POINTS:    	
		optional. It is a vector that specifies the mesh points for the
		spline that represent the fitted DEM, in log(T).
		If not set, the default values 
		[4.,4.5,5.,5.5,6.,6.5,7.,7.5,8.0] are assumed.

	N_ITER:
		optional.It is the number of iterations of the fitting routine.
		If not set, a default value of 20 is assumed. 
		Changing this value alone might not affect the fit, since 
		also the value of DCHISQ_MIN is checked during the fit.

	N_MATCHES:   
		optional.          
		In the unlikely event that more than 50 (default value for 
		N_MATCHES) theoretical lines corresponding to an observed
		line are found, the routine stops; in this case, you have to 
		start again setting N_MATCHES equal to a greater number. 

	OUTPUT  :
		required.
	  	It is the output name. Suffixes will be added when creating 
		the various outputs.

	PHOT:
		optional.
		If set, it means that in the input file the intensities
		are in photons instead of ergs. 

	PLOT_GT:
		optional.
		If set (,/PLOT_GT),  plots of the  G(T) for each 
		observed line not excluded are created.

	PRESSURE:     		
		the value of the pressure (Ne T). Required if you do NOT have
		already the contribution  functions G(T).

	QUIET:
		optional. Set to avoid various messages and the details of the 
		result.

 Calls       : GET_CONTRIBUTIONS
		DEM_FIT
		ZION2SPECTROSCOPIC
		print2d_plot
		
 Common      : obs, 	obs_int,obs_sig,n_obs
		obs_o,	obs_wvl,obs_id,obs_delta_lambda
 		dem, 	d_dem_temp,dem_temp,log_dem_temp,log_t_mesh,log_dem_mesh
		contr,	ch_tot_contr
		ab,	abund_name,abund_info,xuvtop,ioneq_name

		these are the commons with GET_CONTRIBUTIONS.PRO:

		various,	exclu_obs_wvl_no_teo,const_net,$
		 dem_temp_min,dem_temp_max,n_dem_temp,$
		 ch_wvl,ch_l1,ch_l2,ch_id,ch_z,ch_ion,ch_contr_wa,$
		 ch_pop,ch_contr_list,	 ch_term,ch_n_contr

 Restrictions: 
		In the unlikely event that more than 50 (default value for 
		N_MATCHES) theoretical lines corresponding to an observed
		line are found, the routine stops; in this case, you have to 
		start again setting N_MATCHES equal to a greater number. 

		Also, if the starting DEM values are not proper, or you 
		don't have enough constraints at lower and higher temperatures,
		you might get "strange" results, and should consider using 
		different starting values.

		Of course you need to have the enviroment variable CDS_SS_DERE
		pointing to the CHIANTI database top directory.

               
 Side effects: None known yet.
               
 Category    : spectrum
               
 Prev. Hist. :
       Written by Ken Dere (NRL) as part of the CHIANTI package 
       in collaboration with Brunella Monsignori Fossi, Enrico Landi
       (Arcetri Observatory, Florence), Helen Mason and Peter Young
       (DAMTP, Cambridge Univ.). Incorporated into the CDS software.  

 Written     : 
       V. 1.0  5 November  1997 Giulio Del Zanna (GDZ), 
	UCLAN  (University of Central Lancashire, UK)


 Modified    : Removed the print2d_plot subroutine. Increased the default value
               of N_MATCHES from 20 to 50.  Changed way to deal with xuvtop.
               GDZ, 31-Oct-2000

 Version     : 2.0 GDZ, DAMTP,  31-Oct-2000

              V.3, Giulio Del Zanna (GDZ)
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

 VERSION     :  3, 21-May-2002, GDZ 

 Project     : SOHO - CDS     
                   
 Name        : CHIANTI_NE
               
 Purpose     : Calculate and plot CHIANTI density sensitive line ratios.
               
 Explanation : CHIANTI_NE (density ratios)
               calculates and plots density sensitive line ratios based on 
               the CHIANTI atomic database of Dere et. al.
               
 Use         : IDL> chianti_ne
    
 Inputs      : None
               
 Opt. Inputs : None
               
 Outputs     : None
               
 Opt. Outputs: None.
               
 Keywords    : None

 Calls       : CALC_DMM_DR, plot_dmm_dr_fig , make_ion_list

 Common      : dmm_dr_com  dmm_lines(with plot_dmm_dr_fig), 
               
 Restrictions: None
               
 Side effects: None
               
 Category    : Spectral
               
 Prev. Hist. : Started life as 'density_ratios' by Ken Dere

 Written     : C D Pike, RAL, 13-Jan-96
               
 Modified    : Added selection of els/ions from master file.  CDP, 21-Jan-96
               Added hardcopy of line list, refs etc.          CDP, 22-Jan-96
               Include multiple lines in ratio.                 CDP, 27-Jan-96
               General upgrade and added temp/unit selections.   CDP,  6-Jun-97
               Added intensity ratio selection.                 CDP, 17-Jul-97
               Added wavelength ranges.                        CDP, 18-Jul-97
               Fixed typos introduced in version 7.           CDP, 22-Jul-97
               Float the user-supplied Log Temperature.      CDP, 1-Aug-97
               Update for IDL v5.2.                         CDP, 20-Apr-99
               v. 11 Update list of elements.                    CDP, 18-Jun-99

               V.12. Added ratio plots and hardcopies in linear scale, added various
               checks and  minor things. Added a few tags to the 
               ratio output structure (temperature, units, comment). 
               Removed optional output structure. 
               Updated to be CHIANTI v.3-compatible.
               Giulio Del Zanna, DAMTP, 7-Oct-2000 
		Version 13, 21-Dec-2000, William Thompson, GSFC
			Modified for better cross-platform graphics capability

               V. 14, 1-May-02, GDZ, commented out a few refs.
               V. 15,  21-May-2002, GDZ, changed the way to deal with fonts.
               V.16, 17-Sep-2002 (GDZ) 
                    added !p.multi = 0 upon exit and added X-label.


 Version     : Version 16, 17-Sep-2002 

 Project     : SOHO - CDS     
                   
 Name        : CHIANTI_TE
               
 Purpose     : Calculate and plot CHIANTI temperature sensitive line ratios.
               
 Explanation : CHIANTI_TE (temperature ratios)
               calculates and plots temp. sensitive line ratios based on 
               the CHIANTI atomic database of Dere et. al. 
               
 Use         : IDL> chianti_te 
    
 Inputs      : None
               
 Opt. Inputs : None
               
 Outputs     : None
               
 Opt. Outputs: none. 
               
 Keywords    : None

 Calls       : CALC_DMM_TR, make_ion_list

 Common      : dmm_tr_com
               
 Restrictions: None
               
 Side effects: None
               
 Category    : Spectral
               
 Prev. Hist. : Started life as 'temperature_ratios' by Ken Dere

 Written     : H.E. Mason, 3 Oct 1996 

 Modified    : Update for IDL v5.2.  CDP, 20-Apr-99
               V.3.  Update list of elements.  CDP, 18-Jun-99

               V.4 , Giulio Del Zanna (DAMTP), 10 Oct-2000
               Rewritten completely, adding possibility to select the density
               at which the intensities are calculated,  making this routine
               compatible ith CHIANTI v.3, and with the same characteristics as
               CHIANTI_TE. Added ratio plots and hardcopies in linear scale, added various
               checks and  minor things. Added a few tags to the 
               ratio output structure (density, units, comment). 
               Removed optional output structure.
		Version 5, 21-Dec-2000, William Thompson, GSFC
			Modified for better cross-platform graphics capability

               V. 6, 1-May-02, GDZ, commented out a few refs.
               V.7,  21-May-2002, GDZ, fixed a bug with the fonts.
               V.8, 17-Sep-2002 (GDZ) 
                    added !p.multi = 0 upon exit and added X-label

 Version     : Version 8, 17-Sep-2002

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME: ch_check_str

 PURPOSE:
       To check that an input structure is of the right type

 PROCEDURE:
       This function checks that the input structure has at least the  basic
       tags that should be present. Two types of basci structures are checked:
       1) the standard CHIANTI structure, output of the synthetic program
       CH_SYNTHETIC, that contains line INTENSITIES
       2) The standard  CHIANTI structure output of MAKE_CHIANTI_SPEC, that contains a
       synthetic SPECTRUM.
        
 CATEGORY:

	spectral synthesis.

 CALLING SEQUENCE:

       IDL> result=ch_check_str (tran, [/int , /sp])


 INPUTS: the IDL structure TRAN



 OPTIONAL INPUTS :


 OUTPUTS:

 OPTIONAL OUTPUTS:

 KEYWORDS:
        intensities  
        spectrum 

 CALLS: required_tags

 COMMON BLOCKS: none

 RESTRICTIONS:

 SIDE EFFECTS:

 EXAMPLE:

 PREV. HIST. :

 WRITTEN     : 
       Ver.1, 22-May-02, Giulio Del Zanna (GDZ), DAMTP 

 MODIFICATION HISTORY:

 VERSION     : 1, 22-May-02, GDZ

 NAME

     CH_DRAWBOX()

 EXPLANATION

     Allows the selection of a sub-region within a plot using a 
     "rubberband box".

 INPUTS

     WID    ID of window where box is drawn. (!D.Window by default.)

 INTERACTIVE INPUTS

     By clicking-and-holding the left mouse button (LMB), a box will 
     appear on the plot window. Moving the mouse will change the size 
     of the box. When the box is in the right position, let go of the 
     LMB.

 OPTIONAL INPUTS

     COLOR  The color index of the box. (!D.N_Colors-1 by default.)

 KEYWORDS

     DATA   Box coordinates returned in DATA coordinates.

     NORMAL Box coordinates returned in NORMAL coordinates.

 OUTPUT

     The function returns the box coordinates, either in device (default), 
     data or normal coordinates. See keywords /DATA and /NORMAL.

 PREVIOUS HISTORY

     This is a modified version of the routine drawbox.pro that is 
     available from

     http://www.dfanning.com/documents/tips.html

 HISTORY

     Ver.1, 11-Dec-2001, Peter Young

 PROJECT     : CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 

                   
 NAME        : CH_GET_FILE
     		          
 PURPOSE     : to select a file from either a selected directory or the working
               directory, having an extension.

               
 EXPLANATION : a file in  either a selected directory or the working
               directory, having an extension can be selected using a
               widget. Note that both directory and extension have to be
               supplied. If no file is found, an empty string is returned.                   ; 		

 USE         : IDL> name = ch_get_file( '~/', '.pro',  tit=' Select a procedure ')


 EXAMPLES    : dir= concat_dir(!xuvtop),'dem') 
		dem_name=ch_get_file(path=dir,filter='*.dem',title='Select DEM File')
		
    
 INPUTS      : directory, extension 
		
               
 OPT. INPUTS : 

               
 OUTPUTS     : the file name
	
 OPT. OUTPUTS:
		

 KEYWORDS    : title


 CALLS       : findfile, break_file
		
 COMMON      : co
 		
 RESTRICTIONS:  both directory and extension have to be
               supplied. 

               
 SIDE EFFECTS: 
               
 CATEGORY    : 
               
 PREV. HIST. : extracted from CDS/CHIANTI routines.


      
 WRITTEN     : 

       Giulio Del Zanna (GDZ), 
	DAMTP  (University of Cambridge, UK) 

 MODIFIED    : Version 1, GDZ 10-Oct-2000
               V.2, GDZ, corrected a typo at the end of the file.
               V.3, GDZ,  generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

               V. 4, 19-July-2002, GDZ

                Added the option to select files also with the standard IDL
                dialaog_pickfile, and changed a few things...

               V.5, 2-Aug-02, GDZ 
                 reduced the size of the widget.

               V.6, 12-Aug-02, GDZ
                 corrected for a bug in the directory output.

               V.7, 3-Nov-03  GDZ
                 Fixed a bug when using Windows, the returned path was not
                 correct. 

 VERSION     :  7,  3-Nov-03

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 



 NAME:
	CH_LINE_LIST

 PURPOSE:

	Create a latex or an ascii file of predicted spectral line intensities and
       wavelengths corresponding to  selected parameters, as calculated by 
       CH_SYNTHETIC. Needs as input the line intensity structure calculated by
       CH_SYNTHETIC (default)  or the SPECTRUM structure output of
       MAKE_CHIANTI_SPEC.

 CALLING SEQUENCE:

       IDL> ch_line_list, transitions, outname, latex=latex, ascii=ascii, $
       abundfile=abundfile, min_abund=min_abund, $
       wmin=wmin,wmax=wmax,$
       SPECTRUM=SPECTRUM, minI=minI,photons=photons,kev=kev, $
       all=all,no_sort=no_sort, sngl_ion=sngl_ion


 PROCEDURE:


 INPUTS:

       The structure created by CH_SYNTHETIC

 OPTIONAL INPUTS:

	Wmin:   lower limit of the wavelength/energy range of interest (Angstroms)
               if kev keyword set, then wmin is in kev	
	Wmax:   upper limit of the wavelength/energy range of interest (Angstroms)
               if kev keyword set, then wmax is in kev	

       Mini:   Minimum intensity for line to be included in output
	
	SNGL_ION:  specifies a single ion (or a list of ions) to be used instead
                 of the complete set of ions specified in the structure.


       MIN_ABUND:  If set, outputs  only  those elements which 
                   have an abundance greater than min_abund.  

                   For example, from Allen (1973):
                   abundance (H)  = 1.
                   abundance (He) = 0.085
                   abundance (C)  = 3.3e-4
                   abundance (O)  = 6.6e-4
                   abundance (Si) = 3.3e-5
                   abundance (Fe) = 3.9e-5


 KEYWORD PARAMETERS:

       LATEX:  Create a latex file (default, exclusive with /ASCII)

       ASCII:  Create an ascii file (exclusive with /LATEX)

	MINI:	Minimum intensity for line to be included in output

       PHOTONS:  units will be in photons rather than ergs

       KEV:  wavelengths will be given in kev rather than Angstroms

       ALL:  if set, then all lines are included.  This means that lines for which
             only an approximate wavelength is known, denoted by a negative 
             wavelength value in the .wgfa file, are included.
             These lines are listed in the file with a * preceding the wavelength.

       NO_SORT:
             If set, then the lines are *not* sorted in wavelength (or energy).

       SPECTRUM

             If set, IT IS ASSUMED that the input structure is the SPECTRUM
             structure output of MAKE_CHIANTI_SPEC, where the  line
             intensities have already been multiplied by the abundance factor!!


 OUTPUTS:

	A latex (default) or an ascii file with the line list

 CALLS: Many SolarSoft routines.


 COMMON BLOCKS:
        none.

 SIDE EFFECTS:


 EXAMPLE:

             > ch_line_list, trans,'linelist.tex',/latex, wmin=100.,wmax=200.,/all


 CATEGORY:

	spectral synthesis.


 WRITTEN     : 
       Version 1, Written by: Giulio Del Zanna (GDZ) Oct 31 2001.

 MODIFICATION HISTORY:

        V.2, 9-Nov-2001 GDZ. 
                 Now correctly handles the case when no
                 abundances are passed to the routine. 

        v.3, 11-Dec-2001, PRY.
                 Removed calls to get_utc and anytim2cal. Replaced with 
                 call to systime()
 
        v.4, 29-Apr-02, GDZ

                 Fixed a few small bugs, some caused by a change in the
                 database file format for V4. 
                 Added only_mini,  file_effarea keywords to be able to use as
                 input the structure created by MAKE_CHIANTI_SPEC.

        V.5, 22-May-2002, GDZ
                 generalized directory concatenation to work for
                 Unix, Windows  and VMS. changed tags.
                 Changed and added various things, including flabel

        V.6, 12-Aug-02, GDZ
           Modified the output labeling, and fixed two bugs: 1) when /all was used
           the keyword /mini was not working. 2) min_abund was not working
           properly when /spectrum was used.  Reduced size of latex output (was
           12pt)
           Changed output in isothermal case (no Tmax given). Better info printed (GDZ)

        V.7, 3-Nov-03  GDZ
           Modified format e8.2 to e9.2 for Windows compatibility.

        v.8, 18-Jul-2005 GDZ
           Modified the use of the /kev keyword. Also, now the
           routine accepts input structure with the units in keV. 

        v.9, 4-Aug-2005 GDZ
           Corrected a bug introduced in the previous version.
           Also switched to \documentclass when making the latex file.


 VERSION     : 9, 4-Aug-2005

 PROJECT:  CHIANTI

       http://wwwsolar.nrl.navy.mil/chianti.html

       CHIANTI is an atomic database package for the calculation of
       continuum and emission line spectra from astrophysical plasmas. It is a 
       collaborative project involving the Naval Research Laboratory
       (Washington DC, USA), the Arcetri Observatory (Firenze, Italy), and the
       Cambridge University (United Kingdom).


 NAME:
       CH_READ_FITS

 PURPOSE:

       Read  standard CHIANTI FITS binary table data containing the output from
       CH_SYNTHETIC and output a TRANSITIONS structure.

 CALLING SEQUENCE:

       CH_READ_FITS,  Filename, TRANSITIONS

 INPUTS:

       Filename = String containing the name of the CHIANTI FITS file written
       by CH_WRITE_FITS.

 OUTPUTS:

       TRANSITIONS = Structure to be written.

 OPTIONAL INPUTS: none

 KEYWORDS: none


 NOTES:
 

 CALLS:
        MRDFITS, ADD_TAG
	
 COMMON BLOCKS: none.

 RESTRICTIONS:

       (3)     The input FITS file must have been written by  CH_WRITE_FITS

 PREV. HIST. :


 EXAMPLE:

         ch_read_fits,  'file.fits', transitions 

 WRITTEN     : 

       Ver.1, 8-Apr-02 Giulio Del Zanna (GDZ)
       V.2 GDZ 31 May 2002 added more checks.

 MODIfICATION HISTORY:

 VERSION     : 2, 31 May 2002 

 PROJECT

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 

 NAME

     CH_SS

 PURPOSE:
       Widget-based multi-purpose routine 
       to calculate CHIANTI line intensities and continua, to create a 
       synthetic spectrum, to make tables of lines, etc. 

 CALLING SEQUENCE:

       IDL> ch_ss


 PROCEDURE:

     This routine calculates a synthetic spectrum by merging line 
     intensities and continua. 


     The widget is organised into four Sections: 

     SECTION 1:

      -The Calculation of the  CHIANTI line intensities. 
      
       This can be  done in two ways:

       1-Restore a save file with the CHIANTI line intensities already
       calculated.   

       2-Calculate CHIANTI line intensities  with a call to CH_SYNTHETIC. 

       In this case, A series of parameters must be set:

       - Minimum and maximum wavelengths in Angstroms

       - The model used for the calculation. Three are the options:
          1) a constant  density (cm^-3) 
          2) a constant pressure (cm^-3 K) 
          3) a general (Te,Ne) model. In this case, a file will be read.
             This file should have two columns, one with the Te (K)
             values, and one with the Ne (cm^-3) values.

       - The  ionization fraction file to be used.  "*.ioneq"  files
          can be selected from  either  the CHIANTI database, the 
          working directory or selected via a widget.

       - All ions ?  If set to yes (default), then all the ions present in the
                     database will be included.
 
                     If set to no, then it is possible to select a list of ions
                     with a widget 

       - All lines ? If set to no (default), only the lines for which there are
                      observed energy levels are included 
       
                     If set to yes, also the lines that do not have
                     corresponding observed energy levels are included. In this
                     case, the wavelengths are calculated from the theoretical
                     energy levels, and might not be very accurate.
       
       - Isothermal ?  If set to no (default), a DEM file must be selected. 
                         "*.dem"  files (i.e. files with a .dem extension)
                       can be selected from either  the CHIANTI database, the 
                       working directory or selected via a widget.
       
                       If set to yes, then the user is requested to enter one
                       or more temperatures (as logarithmic values - Log T )
                       and correspondent column emission measures EM
                       logarithmic values.
                       NOTE: if more than one value is entered, then the
                             sequence must be  separated by commas (e.g.: 6.0,
                             6.5, 7.), and both Log T and Log EM must have the
                             same number of values 

       - Photoexcitation ?
                       If set to yes, you have to define:
                       Trad: The blackbody radiation field temperature
                       R/Ro: Distance from the centre of the star in stellar
                             radius units 

       Units:  Photons or Ergs'
       
       Protons: If set to Yes, the proton data are used to calculate the level population    


     Once all the parameters have been defined, the user should click on the
     "Calculate intensities" button to start the calculation (which calls 
     CH_SYNTHETIC). 

     Once the calculation is finished, an IDL  structure is loaded into
     memory. It is then possible to save it for later use by clicking  on the
     "SAVE" button. 
      The RESTORE button is to restore previously saved files into an IDL
      structure in memory.

     Once the IDL structure with the line intensities is in the memory, it is
     then possible to calculate and plot a spectrum (SECTION 2).

     SECTION 2:

              This section controls the parameters that are needed to fold the
              line intensities and the continua into a synthetic
              spectrum. These parameters are used by MAKE_CHIANTI_SPEC.

              Before this is done, a set of line intensities MUST be in the
              program memory. This is done either by calculating the
              intensities  or by restoring a save file with
              previously calculated values (SECTION 1). 

              Setting the parameters:

              -Minimum and maximum wavelengths in Angstroms

              -spectrum bin size in Angstroms. Disallowed if an Effective area
                 file is used.
              
              -instrumental FWHM: Setting this to a non-zero value broadens
                                  each of the spectral lines with a Gaussian of
                                  the specified FWHM (in Angstroms) so
                                  mimicking the effects of instrumental
                                  broadening. 
              
              -continuum: Add continua to the binned spectrum:
                          free-free, free-bound and two-photon.
                          Please note that the continuum calculation takes some
                          time and you may want to define a minimum abundance
                          value to speed the calculations.

              - All lines ? If set to no (default), only the lines for which there are
                           observed energy levels are included.
                           If set to yes, the "unobserved lines" will be added, but
                           only if they are present in the structure.


              -elemental abundances
                          "*.abund"  files (i.e. files with a .abund
                         extension) can be selected either from the CHIANTI database,
                          the  working directory, or via a widget. 

              -select a minimum abundance value
                         If set not null, only the lines of those elements
                         which have an abundance greater than the value set are
                         selected. Also, the continuum is calculated only for
                         those elements which  have an abundance greater than
                         the value set. This can significantly speed up the
                         calculations. By default, the minimum value in the
                         selected abundance file is used. To have an idea of
                         what minimum abundance should be set, the abundances
                         of Allen (1973) give: 

                         abundance (H)  = 1.
                         abundance (He) = 0.085
                         abundance (C)  = 3.3e-4
                         abundance (O)  = 6.6e-4
                         abundance (Si) = 3.3e-5
                         abundance (Fe) = 3.9e-5

              
              Eff. Area: Yes/No 

              If you want to fold the spectrum with an effective area.  
              If set to Yes, you are requested to choose an input ascii file
              with two columns, the wavelength and the effective area values
              (cm^2). 
              The wavelenghts in the file (that might not be linear)  are used
              to create the spectrum, that is multiplied with the effective
              area values.
		    Note that this option only works well if a sufficient number
		    of bins is given. The line intensities contributing to each
		    bin are summed, and  subsequently convolved with a gaussian
		    of full-width-half-maximum FWHM, if FWHM is not set = 0.
                   Please note that the convolution might not work if a small
                   number of  bins is defined. 

                Also note that to have the correct output units  (counts s-1
                bin-1) the appropiately scaled DEM (or EM) values must be provided.


              After this, by clicking on the "Calculate and plot" button the
               program calculates and plots the synthetic spectrum. 
              
              Once the spectrum is displayed, it is then possible to
              view the details of the lines by clicking with the mouse in the
              plot window, and to  perform various operations by clicking on
              the buttons in SECTION 3
              
     SECTION 3:

              This Section allows the user to select a few parameters for the
              plotting, and to create different types of OUTPUT.
              
              Labels ? : Setting this to yes plots a vertical line for each
                         spectral line in the spectrum, and also writes a label
                         above the strongest lines indicating the ion from
                         which the line arises. 
              
              Min.:      Only lines which have an intensity greater than  the
                         value set here will be listed and, if requested,
                         labelled and selected for inclusion in the various
                         outputs.  Setting the value=0.  will result in all
                         lines being listed and written in the outputs.
              
              X,Y, XOOM, UNZOOM: It si possible to select a region of the
                                 spectrum, by zooming with the use of the mouse
                                 or by setting the X,Y ranges.

                                NOTE that only the line details and portion of
                                the spectrum shown will be output.

              LINEAR/LOG  To plot the spectrum in linear or log scale
 
              Create PS file: A postscript file is created. 

              Hardcopy: the postscript file "idl.ps" is created and sent to the
                        default printer. 
              
              Save Line details (latex): The  details of the lines shown in the
                                         plot will be  saved in a latex file.
              
              Save Line details (ascii): The  details of the lines shown in the
                                         plot will be  saved in an ascii file.
              
              

              Save Spectrum (ascii): The  X,Y values of the plot are saved in
                                     an ascii file.

              Save Spectrum (IDL/FITS): The details of all the lines and the arrays
                                   of the X,Y values of the plot are saved into
                                   an IDL or FITS file. The  IDL structure 
                                   has the following tags: 

            .LAMBDA:   The array of wavelength X values

            .SPECTRUM: The array of spectrum Y values

            .UNITS       The units of LAMBDA, SPECTRUM 
            .INSTR_FWHM  The Instrumental FWHM
            .BIN_SIZE         Width of the Bins  (fixed) in angstroms
            .ABUND_NAME  The CHIANTI abundance file name
            .ABUND       The abundance values
            .MIN_ABUND   The minimum abundance value used
            .ABUND_REF   The references
            .CONTINUUM   The values of the continuum (if
                                                calculated)
            .EFFAREA       The array of effective area
                                      values (optional)
            .FILE_EFFAREA  The name of the effective area file used (optional).


            .IONEQ_NAME     The ion balance file used (full path).
            .IONEQ_LOGT        The Log10 T values associated.
            .IONEQ_REF      The references.

            .DEM_NAME       The differential emission measure file eventually  used
                            (full path).
            .DEM            The Log10 DEM values 
            .DEM_LOGT          The Log10 T values associated.
            .DEM_REF        The references.

            .MODEL_NAME    A string indicating the model used 
                     (e.g. constant density or constant pressure).

            .MODEL_NE    the Ne value.
            .MODEL_PE    the Pe value.


            .WVL_UNITS  The wavelength units.

            .WVL_LIMITS    The wavelength limits specified by the user.

            .INT_UNITS  The intensity units

            .LOGT_ISOTHERMAL
                       The Log10(T) values used. 

            .LOGEM_ISOTHERMAL
                       The Log10(EM) values used. 

            .TIME      The date and time when the structure was created.

            .VERSION   The version number of the CHIANTI database used.

            .ADD_PROTONS 
                       A flag (0/1) to indicate whether proton data were used (1)
                       or not (0) to calculate the level population.

            .PHOTOEXCITATION
                       A flag (0/1) to indicate if photoexcitation was included (1)
                       or not (0).

            .RADTEMP 
                      The blackbody radiation field temperature used (if
                      photoexcitation was included).

            .RPHOT
                   Distance from the centre of the star in stellar radius units  
                   (if photoexcitation was included).

                                       THEN, FOR EACH LINE USED TO CALCULATE THE
                                       SPECTRUM:

            .LINES     A structure containing information about the lines. 
                       Its size is the number of lines in the spectrum. The 
                       tags are:

                  .peak   The peak intensity value 

                  .iz     The atomic number of the elements (e.g., 26=Fe)

                  .ion    The ionisation stage (e.g., 13=XIII)

                  .snote  The identification of the ion (e.g., 'Fe XXIV d')

                  .ident  The identification of the transition, configuration
                           and terms in text form.

                  .ident_latex
                          The identification of the transition, configuration
                           and terms in latex form.

                  .lvl1   The lower level of the transition (see .elvlc 
                          file for ion)

                  .lvl2   The upper level for transition.

                  .tmax   The temperature of maximum emission of the line 
                          (i.e., the temperature at which the product of 
                          the emissivity and the ion fraction has its 
                          maximum). Rounded to nearest 0.1, and zero in case
                          the isothermal approximation is used. 

                  .fwhm 

                  .wvl    Wavelength of the transition, in Angstroms.

                  .flag   A flag, =-1 if the line has only theoretical energy
                          levels. Otherwise flag=0.

                  .int    Intensity of line  (with the  abundance factor multiplied)



              Save Spectrum (FITS): The entire information contained in the
                                    IDL structure is stored in a FITS file. 
                                    
     SECTION 4:
              Here, text information messages are printed. 

 INPUTS

     None.

 OPTIONAL INPUTS:
     The font 

 OUTPUTS:
     Many.
 
 KEYWORD PARAMETERS:
     
     FONT  the font to be used. Can be useful to customize the appearance of
           the widget.

 CALLS:

     CH_SYNTHETIC, CH_LINE_LIST, CH_DRAWBOX, MAKE_CHIANTI_SPEC, CH_XMENU_SEL,
     plus many other CHIANTI and SolarSoft routines.


 PROGRAMMING NOTES

     Within CH_SS, there are several other routines which are:

     OPLOT_LINES   This overplots lines and a label on the displayed 
                   spectrum.
     SYN_CURSOR    When the mouse is clicked when on the spectrum window, 
                   this routine prints out the list of nearby lines and 
                   their IDs in the text window.

     CALC_SYN_SPECTRUM
                   Calculates line intensities with a call to CH_SYNTHETIC

     PLOT_SYN_SPECTRUM  This calls make_chianti_spec to produce the 
                        intensity vs. wavelength plot.
     SYN_MAIN_EVENT  This handles the widget operations

     SYN_WID       This creates the widgets.     

 COMMON BLOCKS:
        many

 RESTRICTIONS:

 SIDE EFFECTS:

 EXAMPLE:

     IDL> ch_ss

 CATEGORY:
	
	spectral synthesis.


 WRITTEN     : 

       Ver.1, 7-Nov-01, Giulio Del Zanna (GDZ) and Peter Young (PRY)  

 MODIFICATION HISTORY:

       V.2, 7-Nov-01, GDZ . Fixed a small bug (now the spectrum plot is always
       plotted within the widget), and modified the option to add continua.
       Changed the suggested  names of the outputs. 
       Corrected a bug when creating an IDL save file with the spectrum, when
       no line details are present.

       V.3 28-Jan-02 GDZ
           fixed a bug in the density text widget, added a few buttons 
           and options, including the effective area.
            Added noprot, rphot, radtemp keywords to the call to ch_synthetic

       V 4, 18-Apr-2002, GDZ 
           Added  photoexcitation, changed IDL save files to FITS files,

       V.5, 21-May-2002, GDZ 
        fixed a few small bugs: checking min_abund before calculating the
                                spectrum; checking the ioneq file when
                                restoring the structure; changed the status of
                                all lines;  chnaged the font system.
                               generalized directory concatenation to work for 
                               Unix, Windows  and VMS.

       V.6, 15-July-2002, GDZ - New major revision.

           Changed the chianti top directory (for Effective areas).
           Changed  Linear/Log button. 

            Rearranged the sizes of the buttons and added a special cursor to
            highlight the area where  details of the lines will be given. Works
            only in linear scale.

           Added quite a lot of new checks to avoid crashes and
           fixed the problem with the zoom/unzoom/change units.

       V.7, 2-Aug-02, GDZ

           Modified the output labels on the plot, inside and on the axis.
           Also modified a few minor things like the appearance of the Log T,EM
           values. 
           Fixed a bug when creating the latex output.
           Now it restores at the end  previous colors and settings. 
 
       V.8, 8-Aug-02, GDZ
           Changed the CHIANTI system variables. Fixed.
           Also fixed a problem with the element ab. file.

      V.9, 13-Aug-02, GDZ 

           Restored the correct use of ch_line_int, now only the lines in the
           plot window are listed, and the ALL keyword is in use. 
           Now the correct xrange is loaded into COMMON when line int. are
           restored. Now it checks if all ions were in the structure, when
           restoring the line intensities, and flags the widget button accordingly.
           Added a device,decomposed=0. to remove problems with colors.
           Corrected the use of the DEM, IONEQ and ABUND pulldown menus,
           avoiding conflicts between files in the working and CHIANTI
           directory having the same name.
           Added printing of references for ancillary files, and a check on the
           element abundances vs. the elements present in the structure.

       V.10, 7-Nov-03  GDZ

          Modified format e8.2 to e9.2 for Windows compatibility.
          Replaced f9.4 with f11.4 format for the wavelengths.
          Some minor modifications to the widget.

          Added extended details in the ascii output spectrum.

          Added more explanations in the HELP buttons.

       V.11,  22-Jul-2005  GDZ 

          -Added keV option and a few more extra checks.

       V.12,  2-Aug-2005 GDZ
           put RETAIN=2 in the main plotting window.

 TO DO LIST:
           Control the range of Angstroms when clicking
           kev
           Allow plots in intensities instead of intensities A-1

 VERSION     :  V.12,  2-Aug-2005

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	CH_SYNTHETIC

 PURPOSE:

       to calculate CHIANTI line intensities or G(T) and output an IDL structure. 

 PROCEDURE:

       This routine calculates as default line intensities for a user-specified 
       differential emission measure and ionisation balance. The actual 
       creation of a synthetic spectrum (i.e., wavelength vs. intensity) 
       is performed by other routines - see CH_SS.PRO and 
       MAKE_CHIANTI_SPEC.PRO.

       Note that this routine does not include the element abundances 
       in the line intensities, as this will be performed by 
       make_chianti_spec. One of the reasons why  element abundances are not
       included in the line intensities calculation is so that it is easier 
       for the user to see how  modifying abundances affects their spectra in
       e.g. CH_SS.PRO. 

       The calculations are performed at constant pressure or 
       at constant density.

       The routine can also output line intensities calculated with an
       isothermal approximation.

	If the isothermal approximation is not used, then the user will be asked
	to select two  files, that can either be in the 
	standard CHIANTI database or in the working directory. 

       These files are: 
       
       - an ionization fraction file 
       - a differential emission measure (DEM) file.

       The routine can also output the contribution functions G(T) of the lines,
       instead of the intensities, if the keyword GOFT is used. In this case,
       only the ionization equilibrium file needs to be selected.
       The G(T), or intensity per emission measure, is calculated as:

        G=(hc/lambda_ij)*A_ji*(N_j(X^+m)/N(X^+m))*(N(X^+m)/N(X))/ N_e /(4.*!pi)

       where A_ji is the A-value of the transition;
             (N_j(X^+m)/N(X^+m)) is the population of the upper level,
             calculated by solving the statistical equilibrium equations; 
             (N(X^+m)/N(X)) is the ionization equilibrium
             N_e is the electron density.

       unless    /PHOTONS is set, in which case the  (hc/lambda_ij) factor
       is not included.  

       If not specified otherwise, with the use of the MASTERLIST or SNG_ION
       keywords,  then the standard masterlist of the ions, which has 
       all the ions in the current CHIANTI database, is used.

       PROGRAMMING NOTES

       The DEM is not assumed to be specified at 0.1 logT intervals (which 
       is how the ion fraction are specified). Thus this routine reads 
       in the DEM vs. logT information and then uses the IDL spline 
       function to tabulate the DEM over 0.1 logT intervals. The minimum 
       and maximum temperatures are those in the DEM file, rounded up to 
       the nearest 0.1. The new DEM function tabulated over 0.1 logT 
       intervals is contained in 'dem_int'.

       For some of the dielectronic files, radiative decays that were in 
       the standard .wgfa file will also be present in the dielectronic 
       version of the .wgfa file. In these cases the line intensity 
       produced from the latter file needs to be ignored and so we have a 
       check in ch_synthetic to do this. An example is the 1-7 decay in 
       the ca_19.wgfa and ca_19d.wgfa files. In the latter case, the 
       model of the ion does not include electron excitation to level 7 
       and so the model for the 1-7 decay is incorrect, hence we ignore 
       it.

 CATEGORY:

	spectral synthesis.

 CALLING SEQUENCE:

       IDL> ch_synthetic,wmin,wmax, output=output, pressure=pressure,$
            [MODEL_FILE=MODEL_FILE, err_msg=err_msg, msg=msg, $
            density=density,all=all,sngl_ion=sngl_ion, $
            photons=photons,  masterlist=masterlist, $
            save_file=save_file , verbose=verbose, $
            logt_isothermal=logt_isothermal,$
            logem_isothermal=logem_isothermal,$
            goft=goft, ioneq_name=ioneq_name, dem_name=dem_name,$
            noprot=noprot, rphot=rphot, radtemp=radtemp, progress=progress ]



 INPUTS:

	Wmin:  minimum of desired wavelength range in Angstroms
	Wmax:  maximum of desired wavelength range in Angstroms

       PRESSURE:  pressure in emitting region (Pe,  cm^-3 K). 
                  Only a single value is accepted, and the calculation is
                  performed at constant pressure.


 OPTIONAL INPUTS :

       DENSITY:   density in emitting region (Ne, cm^-3). 
                  Only a single value is accepted, and the calculation is
                  performed at constant  density, unless LOGT_ISOTHERMAL is
                  defined. In this case, DENSITY can be an array of values, but
                  has to have the same number of elements as LOGT_ISOTHERMAL.


       MODEL_FILE    Full path of the (Te,Ne) file if defined. 
                     This file should have two columns, one with the Te (K)
                     values, and one with the Ne (cm^-3) values. If these
                     values are not sorted in ascending order of Te, the
                     routine does sort them.
                     


	SNGL_ION:  specifies  a single ion (e.g. SNGL_ION='Fe_10' to include
                 only Fe X lines) or an array (e.g. SNGL_ION=['Fe_10','Fe_11']
                 to include only Fe X and Fe XI lines) of ions to be used
                 instead of the complete set of ions specified in
                 !xuvtop/masterlist/masterlist.ions 

       MASTERLIST: string of a specific masterlist file (full path). 
                   If defined as a keyword (i.e. MASTERLIST=1 or /MASTERLIST)
                   then a widget allows the user to select a  user-defined
                   masterlist file. Shortcut for SNGL_ION.   



	IONEQ_NAME:  Name of the ionization equilization name to use.  If not
		     passed, then the user is prompted for it.

       DEM_NAME:  Name of the DEM file to used.  If not passed, then the user
		   is prompted for it.

       LOGT_ISOTHERMAL
                  Array of logarithmic temperatures.
                  If defined, the emissivities are calculated with an
                  isothermal approximation. The values are sorted in ascending
                  order.

       LOGEM_ISOTHERMAL
                  Array of logarithmic emission measures.
                  If defined, the emissivities are calculated with an
                  isothermal approximation. The values are sorted in ascending
                  order. If LOGT_ISOTHERMAL is specified without 
                  LOGEM_ISOTHERMAL then the emission measures are set to 1 
                  (logem_isothermal=0).

       RADTEMP   The blackbody radiation field temperature (default 6000 K).

       RPHOT    Distance from the centre of the star in stellar radius units.
                I.e., RPHOT=1 corresponds to the star's surface. (Default is
                infinity, i.e., no photoexcitation.)


 OUTPUTS:

       OUTPUT:    The name of the structure containing the line intensities and
                  details.  
                  The tags of the  structure are:

       .lines     A structure containing information about the lines. 
                  Its size is the number of lines in the spectrum. The 
                  tags are:

                  .iz     The atomic number of the elements (e.g., 26=Fe)

                  .ion    The ionisation stage (e.g., 13=XIII)

                  .snote  The identification of the ion (e.g., 'Fe XXIV d')

                  .ident  The identification of the transition, configuration
                           and terms in text form.

                  .ident_latex
                          The identification of the transition, configuration
                           and terms in latex form.

                  .lvl1   The lower level of the transition (see .elvlc 
                          file for ion)

                  .lvl2   The upper level for transition.

                  .tmax   The temperature of maximum emission of the line.

                          If the G(T) are output, tmax is the maximum of G(T).

                          If the isothermal approximation is used  tmax=0.

                          If a DEM is used,  tmax is the maximum of the 
                          emissivity that includes the product of the ion
                          fraction and the DEM.
                          Rounded to nearest 0.1

                  .wvl    Wavelength of the transition, in Angstroms.

                  .flag   A flag, =-1 if the line has only theoretical energy
                          levels. Otherwise flag=0.

                  .int    Intensity of line (erg/cm2/s/sr or phot/cm2/s/sr), 
                          divided by the element abundance (exclusive with .goft). 

                  .goft   The G(T) of the line (optional /exclusive with .int).


       .ioneq_name     The ion balance file used (full path).
       .ioneq_logt        The Log10 T values associated.
       .ioneq_ref      The references.

       .dem_name       The differential emission measure file eventually  used
                       (full path).
       .dem            The Log10 DEM values 
       .dem_logt          The Log10 T values associated.
       .dem_ref        The references.

       .model_name    A string indicating the model used: 

                    1- Constant density
                    2- Constant pressure
                    3- Function (Te,Ne)

       .model_file    Full path of the (Te,Ne) file if defined. Null string otherwise.

       .model_ne    the Ne value(s).

                     - a scalar if 'Constant density' is selected.
                     - an array if 'Function' is selected.
                     - 0. if constant pressure is selected.

       .model_pe    the Pe value.

                     - a scalar if constant pressure is selected.
                     - 0. if 'Constant density' is selected.
                     - an array=density*temperature if 'Function' is selected.
                          
       .model_te    the Te values if 'Function' is selected. Otherwise 0.

       .wvl_units  The wavelength units.

       .wvl_limits    The wavelength limits specified by the user.

       .int_units  The intensity units.

                   1) If LOGT_ISOTHERMAL is defined, we have two cases:
                      a) LOGEM_ISOTHERMAL is not defined, and is therefore
                         assumed to be 0 (EM=1). In this case, units are
                         'photons cm+3 sr-1 s-1' or 'erg cm+3 sr-1 s-1'.
                      b)  LOGEM_ISOTHERMAL is defined. In this case, units are
                         'photons cm-2 sr-1 s-1' or 'erg cm-2 sr-1 s-1'.

                   2) If LOGT_ISOTHERMAL is not defined, we have two cases:
                      a) intensities are calculated. In this case, units are
                         'photons cm-2 sr-1 s-1' or 'erg cm-2 sr-1 s-1'.
                      b) Contribution functions G(T) are calculated. In this
                         case, units are 
                         'photons cm+3 sr-1 s-1' or 'erg cm+3 sr-1 s-1'.

       .logt_isothermal
                  The Log10(T) values used. 

       .logem_isothermal
                  The Log10(EM) values used. 

       .date      The date and time when the structure was created.

       .version   The version number of the CHIANTI database used.

       .add_protons 
                  A flag (0/1) to indicate whether proton data were used (1)
                  or not (0) to calculate the level population.

       .photoexcitation
                  A flag (0/1) to indicate if photoexcitation was included (1)
                  or not (0).

       .radtemp 
                 The blackbody radiation field temperature used (if
                 photoexcitation was included).

       .rphot
              Distance from the centre of the star in stellar radius units  
              (if photoexcitation was included).


 OPTIONAL OUTPUTS:


       SAVE_FILE: If defined, then an IDL save file is created, with the output
                  structure. 


       GOFT:      If set,  the G(T) of the lines are calculated, and put in
                  the output structure, instead  of the line intensities.
                  Units are 'photons cm+3 sr-1 s-1' or 'erg cm+3 sr-1 s-1'



 KEYWORDS:


       ALL:  if set, then all lines are included.  This means that lines for
             which  only an approximate wavelength is known, 
             denoted by a  negative wavelength value in the .wgfa file, are
             included. These are the lines for which there are no observed
             energy levels. 


       PHOTONS:   The output intensities will be in photons instead of 
                  ergs.

       VERBOSE:   If set, the routine will list each ion it is looking at, 
                  and how many lines from each ion it is including in the 
                  spectrum.

       GOFT:      If set,  the G(T) of the lines are calculated, and put in
                  the output structure, instead  of the line intensities.
                  Units are 'photons cm+3 sr-1 s-1' or 'erg cm+3 sr-1 s-1'

       NOPROT     Switch off the inclusion of proton rates in the level 
                  balance (default).

      PROGRESS    If set, a widget appears, showing the progress of the
                  calculation and allowing the user to halt the calculation.

      NO_SUM_INT  Prevents the summing of intensities over temperature. 
                  Only works in conjunction with the LOGT_ISOTHERMAL 
                  option, and is implemented in order to work the 
                  ISOTHERMAL routine. The .INT tag in OUT.LINES becomes 
                  an array with the same number of elements as 
                  LOGT_ISOTHERMAL, corresponding to the intensities at 
                  each temperature.

 CALLS:  CH_GET_FILE
          many CHIANTI standard routines,  including:
          READ_IONEQ, READ_DEM, READ_MASTERLIST, ION2SPECTROSCOPIC,
          ZION2FILENAME, READ_WGFA,READ_ELVLC,READ_SPLUPS,POP_SOLVER,
          DESCALE_UPS, CONVERT_TERMS. 
          CONVERT_TERMS uses some standard SolarSoft routines: 
          REPSTR, STR_INDEX, DATATYPE, 
          VALID_NUM, DELVARX, INFO_PROGRESS, SAVEGEN

 COMMON BLOCKS:
          wgfa, wvl,gf,a_value
          upsilon,splstr
          elvlc,l1a,term,conf,ss,ll,jj,ecm,eryd,ecmth,erydth,eref 
          elements,abund,abund_ref,ioneq,ioneq_logt,ioneq_ref
          radiative, radt, dilute
          proton, pstr
          ionrec,rec_rate,ci_rate,temp_ionrec,luprec,lupci,status

 RESTRICTIONS:

 SIDE EFFECTS:

 CATEGORY:
	spectral synthesis.
	
 EXAMPLE:

       This routine can be called in this way:

       IDL> ch_synthetic,5.,10., output=structure, pressure=1.e+15

       To make use of the output structure, use MAKE_CHIANTI_SPEC or CH_SS
       

 PREV. HIST. :
       Based on synthetic.pro, written by Ken Dere


 WRITTEN     : 
       Ver.1, 22-Jun-00, Peter Young (PRY) and Giulio Del Zanna (GDZ)

 MODIFICATION HISTORY:

       Ver.1, 22-Jun-00, Peter Young and Giulio Del Zanna

       Ver.2, 25-Jul-00, PRY
               Removed /all keyword; make_chianti_spec can be 
                used to filter out negative wavelengths.
               Added flabel tag to output in order to pick out 
                dielectronic recombination lines.

       Ver.3, 4-Oct-00, PRY
               Replaced /all keyword.
               Corrected bug when .wgfa files contain two A-values 
                for the same transition.

       Ver.4, 5-Oct-00, PRY
               Corrected bug that gave rise to lines from the same 
                transition when the dielectronic file existed.

       V.5, 11-Oct-2000, GDZ
            eliminate the abundance call; reinstate the /masterlist keyword;
            added the tag  ident_latex to have the identification in 
            late-style format; added a tag flag=-1 for the unobserved lines,
            and =0 otherwise; reinstated all wavelengths > 0. ;
            added the calculation of the G(T);
            added  a few other tags in the output, and various checks and
            comments. 
       V.6 15-Oct-2000 ,GDZ
             Replaced calls to solarsoft routines to  standard IDL ones. 
             Corrected an error in the output creation, in relation to the
             isothermal case. Added isothermal in the output. added checks to
             the wavelengths. Default output name is TRANSITIONS. changed
             const_net and added const_net_value + a few other things.

       v.7, 27-Nov-2000, GDZ. Corrected an error in the calculation of the
       G(T). 

       Version 8, 5-Dec-2000, GDZ, DAMTP. Fixed a bug when checking the 
       values in the .splups files.

       V. 9, GDZ, 10-Apr-2001, corrected another error in the G(T) calc.

       V. 10, GDZ, 30-Oct-2001 added CHIANTI Version number, changed isothermal
            to logt_isothermal and added logem_isothermal to the output.
            Removed the use of log T values, and the calculation. 
            Added err_msg, a text string with an error message.
 
       Version 11, 8-Nov-01, GDZ

            Changed the MASTERLIST keyword. Allowed double use, as a keyword 
            and as a string.

       Version 12, 18-Nov-01, Peter Young

            Added /NOPROT, RPHOT and RADTEMP keywords; changed upsilon 
            common block.

        Version 13, 29-Apr-02, GDZ

            Added no_protons, photoexcitation, rphot, radtemp 
            tags into the output  structure. 
            Revised Header. Added the PROGRESS widget.
            Added a check if the ion is present in the Ion. Frac. file.
            Added informative MSG keyword.
            Now uses  savegen.pro to save the structure.

        V. 14, 28-May-2002, GDZ: 
                  generalize directory concatenation to work for Unix, Windows
                  and VMS. 

           modified tags: 
                          limits -> wvl_limits
                          ioneq_t -> ioneq_logt
                          wvlunits -> wvl_units
                          intunits -> int_units
                          time --> date 
                          no_protons -> add_protons
                         dem_t -> dem_logt 
                const_nte -> model_name
                const_nte_value -> model_ne, model_pe, model_te
                   removed from the main STR:   .ioneq  ctemp 
                   removed from the LINES STR:  fwhm flabel

            Added model_file  input for model Ne(T). Had to considerably
            modify the routine.

         V. 15, 16-Jul-2002, Peter Young
                  Added keyword /NO_SUM_INT.

         V. 16, 22-Jul-2002, Peter Young
                  Corrected a bug related to /NO_SUM_INT; logt_isothermal 
                  can now be specified without logem_isothermal.

         V. 17, 23-July-2002, GDZ
                  Modified a few checks on the input. Also, now it prints the
                  error message whenever the program aborts

         V.18, 2-Aug-02, GDZ
                  Replaced all DBLARR and DOUBLE calls with floats.
                  Added a comment at the end of the routine when it finishes.

         V.19, 8-Aug-02, GDZ 
                  Added more error info. Changed the use of the DENSITY
                  keyword. It is possible to input an array of values if
                  LOGT_ISOTHERMAL is defined.

         V. 20, 17-Sep-02, GDZ
                  Corrected a bug: the functional (T,N) form
                  is now only accepted if DENSITY is an array with at least two
                  values.
         V. 21, 19-Sep-02, GDZ
                  Corrected the definition of the UNITS in case LOGT_ISOTHERMAL
                  is defined.

         V. 22, 19-Aug-03, Peter Young
                  when logem_isothermal is input, the derived EM is now a
                  DOUBLE array rather than FLOAT, preventing infinities when
                  logem_isothermal values are large.

         V. 23,   4-Oct-2003, GDZ
                  modified the input to POP_SOLVER, now it is dealt with an
                  input structure.

         V.24,    10-Oct-2003, K.Dere
                  added modifications from K.Dere, regarding the satellite
                  lines. 

         V 25,    3-Nov-2003, GDZ
                 Added GROUP keyword, and modified so the progress widget can
                 be stopped within IDL Windows.

         V 26,    17-Apr-2004, Enrico Landi (EL)
                  Added the recombination/ionization population processes.

         V.27,    13-Apr-2005, EL
                  Replaced the main loop to calculate individual line intensities
                  with operations among arrays, to speed the whole program in case
                  of large numbers of lines.

 VERSION     : 27,    13-Apr-2004

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
       CH_WRITE_FITS

 PURPOSE:
       Write  standard FITS binary table data from CHIANTI input  structure.

 CALLING SEQUENCE:
       CH_WRITE_FITS, Input, Filename

 INPUTS:

       Input = Structure to be written to FITS file.


 OUTPUTS:


       Filename = String containing the name of the file to be written.
                CH_WRITE_FITS creates two binary table extension in a single
                FITS file. The second one is appended as a new extension.

 OPTIONAL INPUTS:  Header COMMENTS.

 KEYWORDS: 
           head1, head2
          Additional  COMMENTS to be added at the bottom of the two binary tables.


 NOTES:
 
       Any existing FITS file can be over-written or not.
       Use CH_READ_FITS  to convert the FITS file back into a structure. 

 CALLS:

	FXPAR(), FXADDPAR, IS_IEEE_BIG(), HOST_TO_IEEE, DIALOG_MESSAGE

 COMMON BLOCKS: none.

 RESTRICTIONS:
       (1)     Limited to 127 columns in tables by IDL structure limits.
       (2)     String columns with all columns of zero length crash the
               program
       (3)     The input structure has to be of the type TRANSITIONS.

 PREV. HIST. :

       The subroutines in this procedure are extracted without modifications from
       the MWRFITS.PRO routine, written by T. McGlynn Version 0.95 2000-11-06
       and present in the ASTRON library (in SolarSoft under /gen/idl_libs/astron/).

 EXAMPLE:

         ch_write_fits, transitions , 'test.fits'

 WRITTEN     : 
       Ver.1, 22-May-02 Giulio Del Zanna (GDZ)


 MODIfICATION HISTORY:

 VERSION     : 1, 22-May-02, GDZ

 NAME: 
	CH_XMENU_SEL

 PURPOSE:
     	Allow user to select a set of items from a list.  Widget equivalent
	of WMENU_SEL

 CALLING SEQUENCE:
       ss = ch_xmenu_sel(array)
       ss = ch_xmenu_sel(array, /one)
       ss = ch_xmenu_sel(array, /fixed) - use fixed font (keep column alignement)

 INPUTS:
       ARRAY       A string or string array of values to be displayed for
		    selection
 OPTIONAL KEYWORD INPUT:
	ONE	    If set then only one button may be turned on at a time.
	TIT	    The title of the widget
	GROUP	    The parent widget id (so that if the parent widget exits,
		    this widget is destroyed too)
       FIXED_FONT  If set, use fixed font (keep columns aligned)
       SIZE_FONT   Size of (fixed) font to use - default=15 (implies /FIXED)
       NLINES      How many lines to display.  Default is 20

 OUTPUTS:
	The result returns the select indices of the array ARRAY.

 RESTRICTIONS:
	Must have widgets available.

 HISTORY:
	Written 30-Jan-95 by M.Morrison using Elaine Einfalt
	YO_TAPE_WIDG as a starting point
	10-Jul-96 (MDM) - Ajustment to make the output scaler if it
			  is a single item
       11-nov-96 (SLF) - add FIXED_FONT and SIZE_FONT keywords
	15-Apr-97 (MDM) - Re-added the 9-Jan-97 (MDM) modification
			  to merge with 11-Nov-96 version
			      9-Jan-97 (MDM) - Added NLINES option
	22-Jul-97 (MDM) - Added call to WMENU_SEL if the device is
			  not X (so that terminal prompting is
			  enabled.

       9-may-2001 Giulio Del Zanna (GDZ) 
        added keywords  text and include, renamed ch_xmenu_sel

       V.7, 15-Aug-2002 GDZ 
         Modified a few cosmetics, and add the option to have a TEXT string
         array to add as a comment in the top widget.
    
       V.8  30 Jan 2002, GDZ
          Now it returns an ordered list, according to how the lines where
          selected. It works only the first time the routine is called.

       V.9, 30-Jun-2003, Peter Young
          Added call to CHIANTI_FONT to correct problem with fixed font in 
          Windows.
       V.10 3-Oct-2003, GDZ 
          inserted the ,/MODAL keyword within the main widget, for 
          compatibility with IDL v.5.4

 VERSION     :  10 3-Oct-2003

 NAME

   CI_REC_INTERP()

 PROJECT

   CHIANTI

 EXPLANATION

   For including ionization and recombination into the level balance, it's
   necessary to interpolate the data stored in the CHIANTI files and, in
   addition, perform extrapolation to lower or higher temperatures.

   This routine performs the interpolation and extrapolation for general
   input arrays.

 INPUTS

   TEMP   Temperature at which rate required. Units: K. Must be a scalar
          quantity.

   RATE_TEMP  Temperatures at which RATE is tabulated. Input as Log (base 10)
              values.

   RATE   The rate coefficient, tabulated at temperatures RATE_TEMP.

 KEYWORDS

   EXTRAP_ABOVE Extrapolation to higher temperatures will only take place
                if this keyword is set.

   EXTRAP_BELOW Extrapolation to lower temperatures will only take place
                if this keyword is set.

 OUTPUT

   The value of the rate coefficient at the temperature TEMP. If no data is
   available at the specified temperature then a value of zero is returned.

 HISTORY

   Ver.1, 29-Jun-2005, Peter Young
       adapted from original code by Enrico Landi

 PROJECT:  CHIANTI

       CHIANTI is an atomic database package for the calculation of
       continuum and emission line spectra from astrophysical plasmas. It is a 
       collaborative project involving the Naval Research Laboratory
       (Washington DC, USA), the Arcetri Observatory (Firenze, Italy), and the
       Cambridge University (United Kingdom).

 NAME:
	CONF2N

 PURPOSE:

	Extract the highest principal quantum number from the configuration


 CALLING SEQUENCE:

       CONF2N,conf,n


 INPUTS:

	Conf:  the configuration returned from read_elvlc_direct

	
 KEYWORD PARAMETERS:

	None

 OUTPUTS:

	N:  the principal quantum number




 EXAMPLE:

             > conf2n,'2s2.3p 2P1.0',n
             > print,n
             > 3

 CALLS:

       None

 RESTRICTIONS

       If the principal quantum number is 10 or greater, it will not be 
       picked up.

       If the configurations are written in upper case (e.g., 3S2.3P2), 
       then the principal quantum numbers will not be picked up (a value 
       of 0 will be returned).

 MODIFICATION HISTORY:

       Ver.1, April-2000, Ken Dere

       Ver.2, 17-Oct-2000, Peter Young
                removed call to str_index

 PROJECT:  CHIANTI

 PROJECT:  CHIANTI

       CHIANTI is an atomic database package for the calculation of
       continuum and emission line spectra from astrophysical plasmas. It is a 
       collaborative project involving the Naval Research Laboratory
       (Washington DC, USA), the Arcetri Observatory (Firenze, Italy), and the
       Cambridge University (United Kingdom).

 NAME:
	convertname

 PURPOSE:
	Ion names as character strings are converted into
	numerical values (note c_2 is C II or C^+1
	in spectroscopic or atomic notation)

 CATEGORY:
	
	naming utility

 CALLING SEQUENCE:

       CONVERTNAME,Name,Iz,Ion


 INPUTS:
	Name:   such as 'c_2'


 OUTPUTS:

	Iz:  nuclear charge Z  (6 for 'c_2', the equivalent of C II)
       Ion:  ionization stage:  (2 for 'c_2')

 OPTIONAL OUTPUTS

       DIELECTRONIC   Set to 1 if NAME has a 'd' appended to it 
                      (indicating dielectronic recombination data) else 
                      set to 0

 EXAMPLE:

                     > convertname,'c_2',iz,ion
                     > print,iz,ion
                     > 6,2

                     > convertname,'o_6d',iz,ion
                     > print,iz,ion
                     > 8,6

 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	March 1996:     Version 2.0
       October 1999:   Version 3.  by kpd

       Ver.4, 11-Dec-01, Peter Young
           Revised routine, removing ch_repstr call.
           Added DIELECTRONIC optional output.

 PROJECT     :  CHIANTI

       CHIANTI   http://wwwsolar.nrl.navy.mil/chianti.html

       CHIANTI is an atomic database package for the calculation of
       continuum and emission line spectra from astrophysical plasmas. It is a 
       collaborative project involving the Naval Research Laboratory
       (Washington DC, USA), the Arcetri Observatory (Firenze, Italy), and the
       Cambridge University (United Kingdom).
 
                   
 NAME        : CONVERT_TERMS
     		          
 PURPOSE     : 
              to convert the transition information into readable formats.
               

 CALLING SEQUENCE:

       IDL>this_design =  convert_terms(l1, l2, result_latex =result_latex)

 PROCEDURE: 
 		This function is used to convert the transition information into
 		readable formats, including spaces and calulating the J values.
		The process is quite complex since the notation of the level
		designations in the CHIANTI files is not standard. 
		A very useful latex-style output is also created.

    
 INPUTS      : 
		l1:  the index of the lower level
               l2:  the index of the upper level
               
               the rest of the input info is taken from the COMMON.

 OPT. INPUTS : none

               
 OUTPUTS     : 
	        a string with the transition information. 
		
		
 OPT. OUTPUTS:
	       a string with the transition information in latex format. 
	
		
 KEYWORDS    : 
              RESULT_LATEX: the name of an output string.
    

 CALLS       : 		
		CONVERT_CONFIG (included here) and other SolarSoft routines.

		
 COMMON BLOCKS: elvlc,l1a,term,conf,ss,ll,jj,ecm,eryd,ecmth,erydth,eref
 		from here, all the information needed is taken.
		

 RESTRICTIONS: It will not convert every case. 

               
 SIDE EFFECTS: None known yet.
               

 EXAMPLES    : 
		this_design =  convert_terms(l1, l2, result_latex =result_latex)		


 CATEGORY    : 
               spectral synthesis.

 PREV. HIST. :
             parts of the function convert_terms  are derived from the CHIANTI
             routines.  

 WRITTEN     : 

       Giulio Del Zanna (GDZ), 10-Oct-2000 
	DAMTP  (University of Cambridge, UK) 

 MODIFIED    : Version 1, GDZ 10-Oct-2000
               Version 2, GDZ 10-Oct-2001  
               Uses standard SolarSoft routines.
               V. 3, 18-Sep-2002, GDZ 
                Fixed a bug with the jvalue


 VERSION     : 3, 18-Sep-2002

 PROJECT     :  CHIANTI

       CHIANTI   http://wwwsolar.nrl.navy.mil/chianti.html

       CHIANTI is an atomic database package for the calculation of
       continuum and emission line spectra from astrophysical plasmas. It is a 
       collaborative project involving the Naval Research Laboratory
       (Washington DC, USA), the Arcetri Observatory (Firenze, Italy), and the
       Cambridge University (United Kingdom).
 
                   
 NAME        : CONVERT_TERMS_ALL
     		          
 PURPOSE     : 
              to convert level information into readable formats for all the levels
              of an ion.
               

 CALLING SEQUENCE:

       IDL>convert_terms_all, res_ascii, res_latex

 PROCEDURE: 
 		This function is used to convert the level information into
 		readable formats, including spaces and calculating the J values.
		A very useful latex-style output is also created.
               It has been adapted to manage all the levels of a given ion
               at once from the original routine CONVERT_TERMS.PRO.

    
 INPUTS      : all the input info is taken from the COMMON.

 OPT. INPUTS : none

               
 OUTPUTS     : 
	       RES_ASCII: a string array with the transition information in ASCII format. 
		
              RES_LATEX: a string array with the transition information in LATEX format.
    

 CALLS       : 		
		CONVERT_CONFIG (included here) and other SolarSoft routines.

		
 COMMON BLOCKS: elvlc,l1a,term,conf,ss,ll,jj,ecm,eryd,ecmth,erydth,eref
 		from here, all the information needed is taken.
		

 RESTRICTIONS: It will not convert every case. 

               
 SIDE EFFECTS: None known yet.
               

 EXAMPLES    : 
		convert_terms_all, res_ascii, res_latex


 CATEGORY    : 
               spectral synthesis.

 PREV. HIST. :
             convert_terms_all has been derived from the existing CHIANTI
             routine CONVERT_TERMS.

 WRITTEN     : 
             Enrico Landi, 11-Apr-2005
	      Naval Research Laboratory

 MODIFIED    : Version 1, EL 11-Apr-2005


 VERSION     : 1, 11-Apr-2005

 NAME

    CORRECT_POPS()

 PROJECT

    CHIANTI

 EXPLANATION

    Corrects CHIANTI level populations with the ionization and recombination
    rate coefficients

 INPUTS

    PP      The level populations that need to be corrected.

    T       Temperature at which calculation is performed. Units: K.

    XNE     Electron density at which calculation is performed. Units: cm^-3

    IONREC  Structure with the following tags
            .rec        Effective recomb. rate coefficients
            .ci         Effective ionization rate coefficients
            .temp       Temperatures at which rates are tabulated
            .lev_up_rec Levels to which recombination takes place
            .lev_up_ci  Levels to which ionization takes place
            .status     Either +1 (ion/rec data exists) or -1 (dosen't exist)
            .ioneq      Ion fractions of the 3 ions

    CC      2D matrix produced by MATRIX_SOLVER that contains the rate
            coefficents from the standard CHIANTI processes.

 OPTIONAL OUTPUTS

    CRATE   A 1D array of same size as POP containing the collisional
            ionization rate coefficients (units: cm^3 s^-1).

    RECRATE A 1D array of same size as POP containing the recombination
            rate coefficients (units: cm^3 s^-1).

    CORRECTION A 1D array of same size as POP containing the correction
               factors for each level.

    FRAC_LOW The ratio of the current ionization fraction to the fraction
             of the one lower ion (i.e., less ionized).

    FRAC_HIGH The ratio of the current ionization fraction to the fraction
              of the one higher ion (i.e., more ionized).

 CALLS

    ION_FRAC_INTERP(), CI_REC_INTERP()

 HISTORY

    Ver.1, 10-Jun-2005, Peter Young
        Taken original code of Enrico Landi and inserted it into a separate
        routine.

    Ver.2, 16-Aug-2005, Peter Young
        Changed total_exc to be dblarr in order to prevent NaNs.

 Project     : SOHO - CDS     
                   
 Name        : DEM_FIT
               
 Purpose     : Calculates the Differential Emission Measure DEM(T) using
		a set of values in common with other routines.
               
 Category    : diagnostic analysis

 Explanation : This routine (called by CHIANTI_DEM.PRO)   performs
		 a series of iterations in order to
		find the DEM that minimize the chi^2. The values in common 
		with CHIANTI_DEM.PRO are used.
		As a least squares fit to a non-linear
       	function, see pages 237-239, Bevington, Data Reduction and Error
       	Analysis for the Physical Sciences.
               
 Use         : IDL> dem_fit,y,chisqr 
		It has to be noted that a general use of this routine 
		is limited.
    
 Inputs      : the values stored in common. 
                              
 Opt. Inputs : None
               
 Outputs     : log_dem_mesh,y ,chisqr
		i.e. the DEM mesh values, the intensity values as resulted
		from this model DEM, and the chi^2.
 
               
 Opt. Outputs: None
               
 Keywords    : 
		FLAMBDA: the initial value of the parameter flambda.

		SCALE:   the initial value of the parameter scale, that 
			controls the steps of the iteration.

		N_ITER:
		optional.It is the number of iterations of the fitting routine.
		If not set, a default value of 20 is assumed. 
		Changing this value alone might not affect the fit, since 
		also the value of DCHISQ_MIN is checked during the fit.

		DCHISQ_M:
		optional. If not set, a default value of DCHISQ_MIN=1.e-5 
		is assumed. For each iteration, the CHISQ and it's variation 
		are calculated. As long as the iteration achieves an
		improvement in CHISQ greater than  DCHISQ_MIN , another 
		iteration will be performed.

		FAILED: If the fit fails,the routine returns and flags FAILED=1

		QUIET:
		optional. Set to avoid various messages

 Calls       : DEM_DERIV, DEM_FUNCTN, DEM_CHISQR

 Common      : 
               obs,  obs_int,obs_sig,n_obs
               dem,  d_dem_temp,dem_temp,log_dem_temp,log_t_mesh,log_dem_mesh 
		contr,ch_tot_contr
               
 Restrictions: Not always the fit is successful.
               
 Side effects: None known.
               
               
 Prev. Hist. :
       Written by Ken Dere (NRL) as part of the CHIANTI package 
       in collaboration with Brunella Monsignori Fossi, Enrico Landi
       (Arcetri Observatory, Florence), Helen Mason and Peter Young
       (DAMTP, Cambridge Univ.). Incorporated into the CDS software.  

 Written     : 
       Giulio Del Zanna (GDZ), 
	UCLAN  (University of Central Lancashire, UK)  5 November 1997

 HISTORY:

       Ver 1, GDZ  5-Nov-97

       Ver 2,  EL 6-Apr-05
               Renamed the variable "deriv" to "deriv1" to avoid conflicts
               with an IDL routine with the same name.
       
 Version     : 2.0  6 April 2005

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	DENSITY_RATIOS

 PURPOSE:

	to calculate line intensity ratios as a function of electron density

 CATEGORY:

	scientific analysis

 CALLING SEQUENCE:

       DENSITY_RATIOS,Ion,Wmin,Wmax,Dmin,Dmax,Density,Ratio,Description


 INPUTS:

       Ion:   the CHIANTI style name of the ion, i.e., 'c_5' for C V
	wmin:  minimum of the wavelength range of interest in Angstroms
	wmax:  maximum of the wavelength range of interest in Angstroms
       dmin:  log10 of the minimum desired density (8. = 10^8 cm^(-3) )
       dmax:  log10 of the maximum desired density range

 INTERACTIVE INPUTS:

	Must select the line for the numerator and denominator 
       It is possible to select multiple lines to be summed
	
 KEYWORD PARAMETERS:

        OUTFILE:  the (optional) name of the output ascii file where a 
                   listing of the line ratio intensity as a function of 
                   density is saved.  For example, outfile='den_rat.lis'

        PSFILE:  the (optional) name of the output postscript file 
                  where a plot of the choses density sensitive line
                  ratio is saved.  For example, psfile='den_rat.ps'

        TEMP:   to specify the temperature, otherwise the temperature at 
                  the peak 
                  of the ionization equilibrium is used.  For example, 
                  temp=1.e+6

        /PHOTONS:  if set, the ratio will be in photon units, as opposed 
                   to ergs    

	RADTEMP	Specify background radiation temperature (default: 6000 K)

	RPHOT   Distance from the centre of the star in stellar radius units.
               I.e., RPHOT=1 corresponds to the star's surface. (Default is
               infinity, i.e., no photoexcitation.)

       NOPROT  If set, then the default setting will be NOT to use 
               proton rates. This can be changed within the routine.

       VERBOSE To print out information about the lines.

 OUTPUTS:

	Density:  an array of the density values for which the selected 
                   intensity ratio calculated 
       Ratio:    an array of line intensity ratios
       Description:  a string describing the transitions selected

       Plots the intensity ratio of the selected line as a function of density


 COMMON BLOCKS:

       None.

 CALLS

       EMISS_CALC, ION2SPECTROSCOPIC, CONVERTNAME, READ_IONEQ,
       CH_XMENU_SEL

 EXAMPLE:

       density_ratios,'o_5',1000.,1500.,8.,13.,den,rat,desc 

       choose the ratio of 1371.294 to 1218.393 

 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	March 1996:     Version 2.0
       May 28, 1996:  Ken Dere added psfile keyword/option
       Sept 1996:     modified to work with VMS
                      and added keyword TEMP, Ken Dere
       Feb. 2000:     Modified for Version 3, K. Dere
       14-Jul-2000    Peter Young, now calls pop_solver
       26-Sep-2001    Modified for 9-point splines and proton rates; 
                      added radtemp and rphot keywords for photoexcitation.
       20-Nov-2001    Routine now calls emiss_calc to get emissivities.

       V.9, 21-May-2002, Giulio Del Zanna (GDZ) 
                      generalized directory concatenation to work for
                               Unix, Windows  and VMS.
       V.10, 1-Aug-02 GDZ
          Changed all the formats.

       V.11, 06-Aug-02 GDZ
              Changed the use of CHIANTI system variables. 

       V.12, 15-Aug-02, GDZ 
              Major revision:
              -Added the keyword VERBOSE, to avoid printing out long lists of lines.
              -Removed the call to ch_xselect_s, that did not work for long lists.
              -Added a '*' in the line lists, to identify 'unobserved' lines.
              -Replaced the commands to create PS file, to make it
               cross-platform compatible.
              -Added a large number of cosmetics, mainly lables to the axes and
               titles, that were missing.
              -Removed plotting in windows already present.
              -Added the CHIANTI version number in the outputs.

        V.13, 3-Nov-03  GDZ
           Modified format e8.2 to e9.2 for Windows compatibility.

 VERSION     :   13, 3-Nov-03

 PROJECT

       CHIANTI   http://wwwsolar.nrl.navy.mil/chianti.html

       CHIANTI is an atomic database package for the calculation of
       continuum and emission line spectra from astrophysical plasmas. It is a 
       collaborative project involving the Naval Research Laboratory
       (Washington DC, USA), the Arcetri Observatory (Firenze, Italy), and the
       Cambridge University (United Kingdom).

 NAME
        dens_plotter

 PURPOSE:
        A widget-based routine to allow the analysis of density sensitive
        ratios. **** See RATIO_PLOTTER for details. *****

 CALLING SEQUENCE:

       IDL>  dens_plotter,  name,$ 
                  EM, PATH=PATH, NOPROT=NOPROT, $
                  IONEQ_FILE=IONEQ_FILE, ABUND_FILE=ABUND_FILE


 INPUTS:
        The ion name (e.g. 'si_3' for Si III)

 OPTIONAL INPUTS : none

 OUTPUTS:

 OPTIONAL OUTPUTS:

	EM:	Save the displayed emissivities to structure EM.
               **** See RATIO_PLOTTER for details. *****

 KEYWORDS:


	PATH:	Data in the CHIANTI format that is not in the CHIANTI 
		database can be read by specifying the directory in which 
		it lies through PATH.

       ABUND_FILE  The name of a CHIANTI abundance file. This is used for 
               calculating the proton to electron ratio. Default is 
               !abund_file.

       IONEQ_FILE  The name of a CHIANTI ion balance file. This is used for 
               calculating the proton to electron ratio and evaluating 
               the T_max of the ion. Default is !ioneq_file.

       NOPROT  If set, then the default setting will be NOT to use 
               proton rates. This can be changed within the routine.


 CALLS:   CONVERTNAME RATIO_PLOTTER
      

 COMMON BLOCKS: none


 RESTRICTIONS:

 SIDE EFFECTS:

 CATEGORY:
	spectral synthesis.
	
 EXAMPLE:
             IDL> dens_plotter, 'si_9'


 WRITTEN     : 
              Ver.1, 18-Apr-2002, Giulio Del Zanna (GDZ) written as a wrapper
              routine to call RATIO_PLOTTER.

             
 MODIFIED:   V.2,  2-Aug-2005, GDZ
              Now the routine handles the dielectronic case


 VERSION     :   2,  2-Aug-2005

 EXPLANATION

      This routine descales all types of spline fits into upsilons or 
      rates, i.e., it does both electron upsilons and proton rates, 
      and both 5-point and 10-point splines. In addition it can 
      simultaneously descale several temperatures at once.

 INPUTS

      TEMP     Temperature(s), K.

      SPLSTR   Structure output by read_splups.

      INDEX    Index of structure.

 OUTPUTS

      UPS      Upsilon value(s) at temperature(s) TEMP.

 EXAMPLES

      read_splups,splupsfile,splstr
      descale_all,[1.e6,2.e6],splstr,5,ups
      print,ups

 HISTORY

      Ver.1, 15-Mar-01, Peter Young
               adapted from Ken Dere's descale_ups.pro.

      Ver.2, 12-Nov-01, Peter Young
               added type 6 transitions (for protons)

 PROJECT:  CHIANTI

       CHIANTI is an atomic database package for the calculation of
       continuum and emission line spectra from astrophysical plasmas. It is a 
       collaborative project involving the Naval Research Laboratory
       (Washington DC, USA), the Arcetri Observatory (Firenze, Italy), and the
       Cambridge University (United Kingdom).


 NAME:
	DESCALE_UPS

 PURPOSE:

	convert from Burgess-Tully scaling spline fits to Upsilons

 CATEGORY:

	science.

 CALLING SEQUENCE:

       DESCALE_UPS,Index,Jndex,xt,upsilion

 INPUTS:

	Index:	index of lower energy level (lowest level is 1)
	Jndex:	index of upper energy level (lowest level is 1)
	xt:  scaled temperature

 OPTIONAL INPUTS:

	None:
	
 KEYWORD PARAMETERS:

	None:	

 OUTPUTS:

	Upsilon:  the Maxwellian averaged collision strength



 COMMON BLOCKS:

	common elvlc,l1a,term,conf,ss,ll,jj,ecm,eryd,ecmth,erydth,eref
       common wgfa, wvl,gf,a_value
       common upsilon,t_type,c_ups,splups


 PROCEDURE:

	see Burgess and Tully, 1992, Astron and Astrophys, 254, 436.

 EXAMPLE:

             ;
 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	March 1996:     Version 2.0
       December 1998:  Include transition type 5   (kpd)

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 

 NAME: EMISS_CALC()
       
 PURPOSE:

       To compute the emissivities of all lines of a specified ion over
	given ranges of temperature and density.

 CATEGORY:

       Scientific analysis

 EXPLANATION:

 	This routine calculates:

		hc
       	--  * N_j  * A_ji
      	       lamb

 	where hc = 1.986 * 10^-8 erg AA, lamb is in angstroms, N_j is the 
	fraction of ions in the upper emitting level j, and A_ji is the 
	radiative decay rate for the transition.

	The emissivities are stored in a structure called EMISS that also
	holds the wavelength of the transition, the level numbers i and j 
	and also a 'flag', which is set to -1 if the wavelength is negative.

	The temperature and density ranges can be specified directly using
	the TEMP and DENS keywords. Setting TMAX to the log T_max of the 
	ion, gives emissivities for 3 temperatures: log T_max +- 0.15. 
	If DENS is not set, then it is set to 8 to 12 in 0.5 dex intervals. 
	STDENS allows the start density (of 8) to be changed to some other 
	value; ND allows the number of densities to be varied (default 9); 
	DINT allows the density interval to be varied (default 0.5).

 CALLING SEQUENCE:

       EMISS=EMISS_CALC (IZ, ION, [ TEMP=TEMP, DENS=DENS, RADT=RADT, $
				DIL=DIL, PATH=PATH, /NO_DE, /PROTON, $
				QUIET, PRESSURE=PRESSURE)

 EXAMPLES:

	EMISS=EMISS_CALC(26,13)
	EMISS=EMISS_CALC(26,13,temp=[6.2],dens=findgen(5)+8)
	EMISS=EMISS_CALC(26,13,temp=findgen(11)/100.+5.5,press=10.^15)

 INPUTS:

	IZ	The atomic number of the ion

	ION	The spectroscopic number of the ion (e.g., 12 = XII)

 OPTIONAL INPUTS:

	TEMP	Direct specification of the temperature range (log T)

	DENS	Direct specification of the density range (log Ne)

	RADTEMP	Specify background radiation temperature (default: 6000 K)

	RPHOT   Distance from the centre of the star in stellar radius units.
               I.e., RPHOT=1 corresponds to the star's surface. (Default is
               infinity, i.e., no photoexcitation.)

	PATH	If specified, the routine will look for the atomic data in 
		the PATH directory, rather than in the CHIANTI database

	PRESSURE	If a temperature array is given, and PRESSURE set, 
			then the emissivities will be evaluated at the 
			specified temperatures, but for densities = 
			pressure/temperature. If DENS is set, then it will 
			be ignored. The pressure is assumed to be in units 
			K * cm^-3.

       ABUND_FILE  The name of a CHIANTI abundance file. This is used for 
               calculating the proton to electron ratio. Default is 
               !abund_file.

       IONEQ_FILE  The name of a CHIANTI ion balance file. This is used for 
               calculating the proton to electron ratio and evaluating 
               the T_max of the ion. Default is !ioneq_file.

       SUM_MWL_COEFFS  An array of coefficients of the same length as 
                       the array of temperatures. Electron and proton rate 
                       coefficients will be calculated at each temperature 
                       and then a weighted sum of the coefficients is 
                       performed using SUM_MWL_COEFFS. This allows 
                       non-Maxwellian energy distributions to be 
                       incorporated into the level balance equations.
                       This keyword is not compatible with the PRESSURE
                       keyword.

       RADFUNC         The name of a user-defined function that will generate
                       a radiation spectrum as a function of temperature. 
                       This radiation field will replace the black-body that
                       is assumed when using the RADTEMP keyword in the call
                       to pop_solver.

 KEYWORDS:

	NO_DE	Drops the hc/lambda factor in the computation of the 
		emissivities. Useful for emission measure analyses involving 
		photon fluxes

       NOPROT  If set, then the default setting will be NOT to use 
               proton rates. This can be changed within the routine.

	QUIET	If set, don't list the temperatures and densities at which 
		the emissivities are caculated.

       DIEL   If the dielectronic recombination files exist for the ion, 
               then these are used to derive the emissivities.

       NO_SETUP  If emiss_calc is called from a routine where the ELEMENTS
                 common block has already been set up, then this keyword
                 stops emiss_calc loading up the common block

 OUTPUT:

	The structure that is output has the following tags:

	.ion_name	string; contains ion name, e.g., 'Fe XIII'
	.lambda		float; contains wavelength
	.level1		integer; contains lower level of transition
       .lvl1_desc      string; gives config. and term of lower level
	.level2		integer; contains upper level of transition
       .lvl2_desc      string; gives config. and term of upper level
	.flag		integer; a flag to mark particular transitions
	.em		fltarr(nt,nd); contains emissivities at particular 
			  temperatures and densities.

 PROGRAMMING NOTES:

	Transitions where only theoretical energies are available for at 
	least one of the two levels are assigned negative wavelengths in 
	the .wgfa file. With emiss_calc, the wavelength is set to be 
	positive, but emiss.flag is set to -1 for that transition, so 
	that other routines can keep track of the theoretical wavelengths.

 COMMON BLOCKS:

	ELVLC, WGFA, UPSILON, RADIATIVE, PROTON, ELEMENTS, IONREC

 CALLS:

	SETUP_ION, POP_SOLVER
       ZION2FILENAME, ZION2SPECTROSCOPIC
	READ_PROT, PROTON_DENS

 HISTORY:

	Ver 1, PRY 28-Jun-97
	Ver 2, PRY 26-Jul-97  - corrected problem with size of emiss
	Ver 3, PRY 22-Sep-97  - allowed photo-excitation to be included
	Ver 4, PRY 6-Jul-98   - added PATH
	Ver 5, PRY 5-Sep-98   - added call to choose_ioneq
       Ver 6, PRY 3-Dec-98   - dosen't crash if no params given
	Ver 7, PRY 9-Jan-99   - allowed proton rates to be added through 
				/PROTON keyword.
	Ver 8, PRY 10-Feb-99  - added /QUIET keyword
	Ver 9, PRY 8-Oct-99   - for H-like ions, there's a 2-photon 
				transition with a non-zero A-value that is 
				assigned a zero wavelength (as it does not 
				produce an emission line). This caused 
				problems for dens_plotter, so emiss_calc 
				now removes this transition from the emiss 
				structure.
	Ver 10, PRY 15-Dec-99 -	added deu to the upsilon common block in 
				order to be consistent with the main Chianti 
				routines.
	Ver 11, PRY 8-May-00  - added PRESSURE
       Ver 12, PRY 17-Aug-00 - changed elvlc common block to match new 
                               version of pop_solver
       Ver 13, PRY 10-Oct-00 - now calls setup_ion to read ion data
       Ver 14, PRY 1-Jun-00  - removed call to choose_ioneq; now makes use 
                               of the !ioneq_file system variable.
       Ver 15, PRY 25-Sep-01 - modified for 9-point splines and proton rates
       Ver 16, PRY 9-Dec-01  - completed changes for v.4

       V. 17, 29-May-2002, Giulio Del Zanna (GDZ) 
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 
                   Now we only call zion2filename, corrected the call to
                   zion2spectroscopic (dielectronic cases were not handled
                   correctly).

       V.18, 6-Aug-2002, Peter Young
                   Theoretical wavelengths weren't being flagged so this 
                   has now been corrected.

       V.19, 7-Aug-2002, Peter Young
                   Stopped "lines" with zero wavelength being included in 
                   the structure.
                   Changed the use of CHIANTI system variables.

       V.20 14-Aug-2002, GDZ 
                   Modified the use of Version, to make it compatible with the
                   other CHIANTI v.4 routines.

       V.21 10-Sep-2002, Peter Young
                   Allowed a density of 1 cm-3 to be input.

       V.22 7-Aug-2003, Peter Young
                   Added keyword /NO_SETUP

       V.23  4-Oct-2003, GDZ
                  modified the input to POP_SOLVER, now it is dealt with an
                  input structure.

       V.24  5-Mar-2004, Enrico Landi (EL)
                  included ionization and recombination as level population
                  processes

       V.25  6-May-2005, EL
                  corrected a minor incompatibility with IDL 5.6

       V.26  5-Jul-2005, Peter Young
                  added RADFUNC= and SUM_MWL_COEFFS= keywords

       V.27  1-Aug-2005, Peter Young
                  re-ordered code for setup to prevent crash

       V.28  3-Aug-2005,GDZ
                  fixed bug, only define ioneq_ionrec when files are
                  there (it was failing with neutrals)


 VERSION     :   28  3-Aug-2005

 PROJECT:  CHIANTI

       CHIANTI is an atomic database package for the calculation of
       astrophysical emission line spectra.  It is a collaborative project
       involving Ken Dere (Naval Research Laboratory, Washington DC), 
       Brunella Monsignori-Fossi and Enrico Landi (Arcetri Observatory, 
       Florence), and Helen Mason and Peter Young (DAMTP, Cambridge Univ.).

 NAME

	EMISS_SELECT()
       
 PURPOSE

	Allows emissivity arrays within EMISS structures to be selected 
	via a widget.

 CATEGORY:

       Atomic data analysis

 CALLING SEQUENCE

	em=emiss_select(emiss,index,sel_ind=sel_ind)

 EXAMPLES

	emiss=emiss_calc(26,13)       ; calculate emiss for FeXIII
	em=emiss_select(emiss)
	em=emiss_select(emiss,indgen(10))
	em=emiss_select(emiss,wra=[200,300],sel_ind=sel_ind)

 INPUTS

	EMISS	A structure that is output by the routine EMISS_CALC

 OPTIONAL INPUTS

	INDEX	A list of indices that allow a sub-set of wavelengths to 
		be displayed in the widget. If not specified, then 
		complete list of wavelengths is shown.

	WRANGE	Only show wavelengths lying in the specified wavelength 
		range, e.g., wrange=[200,300]

	SEL_IND	Contains the emiss index/indices of the selected 
		wavelengths.

       GROUP   If emiss_select is being called from another widget-based 
               routine, then one needs to set GROUP to the widget ID of 
               the top-level widget.

 OUTPUTS

	An array that contains the emissivities. If two or more lines were 
	selected, then the arrays are added together.

 CALLS


 HISTORY

	Ver.1, PRY 1-Sep-97.
	Ver.2, PRY 23-Feb-99,  added WRANGE keyword
       Ver.3, PRY 13-Sep-00,  changed format of wavelengths in the 
                  widget list
       Ver.4, PRY 20-Nov-00,  removed call to xselect_s - the widget 
                  is now created internally.
       Ver.5, PRY 27-Dec-00,  changed switch to tst1 for IDL v5.4
       Ver.6, PRY 6-Aug-02, added transition information to the widget, 
                  and tidied up some of the code.
       
       V.7, 15-Aug-2002 Giulio Del Zanna (GDZ) 

             Replaced the entire  widget with a call to ch_xmenu_sel.
             This works fine with very long lists of lines, while previously
             the widget was very slow and sometimes would hang.
    
 VERSION     :  7, 15-Aug-2002

 NAME 

     ZETA_0

 EXPLANATION

     Returns the value of zeta_0 (the number of vacancies in the ion given 
     by IZ and ION). See Sect. 2.2 of Mewe et al. (1986, A&AS 65, 511).

 INPUTS

     IZ    Atomic number of ion (e.g., 26 -> Fe)

     ION   Spectroscopic number of ion (e.g., 13 -> XIII)

 OUTPUTS

     Value of zeta_0.

 PROJECT:  CHIANTI

       CHIANTI is an atomic database package for the calculation of
       continuum and emission line spectra from astrophysical plasmas. It is a 
       collaborative project involving the Naval Research Laboratory
       (Washington DC, USA), the Arcetri Observatory (Firenze, Italy), and the
       Cambridge University (United Kingdom).

 NAME:
           FF_RAD_LOSS
	

 PURPOSE:

	Calculate the free-free radiative energy losses losses.
       Uses the free-free integrated gaunt factor calculations of 
       Sutherland, 1998, MNRAS, 300, 321


 CALLING SEQUENCE:

      FF_RAD_LOSS,Temperature,LossRate


 INPUTS:



 OPTIONAL INPUTS:

	None
	
 KEYWORD PARAMETERS:

	NO_SETUP:   If the procedure setup_elements has already been called then
                  the keyword /no_setup should be set to avoid repeating this step

       MIN_ABUND:  If set, calculates the continuum only from those elements which 
                   have an abundance greater than min_abund.  Can speed up the 
                   calculations.  For example:
                   abundance (H)  = 1.
                   abundance (He) = 0.085
                   abundance (C)  = 3.3e-4
                   abundance (Si) = 3.3e-5
                   abundance (Fe) = 3.9e-5


 OUTPUTS:

	Temperature:	temperature in degrees Kelvin, can be a 1 D array
       LossRate:       radiative energy loss rate in erg s^-1 cm^3
                       (radiative loss rate per emission measure (N_e N_H V)



 COMMON BLOCKS:

	common elements,abund,abund_ref,ioneq,ioneq_t,ioneq_ref



 EXAMPLE:

             > ff_rad_loss,t,rad
             > ff_rad_loss,t,rad,min_abund=3.e-5
             > ff_rad_loss,t,rad,/no_setup,min_abund=1.e-6


 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	April 2000:     Version 3.0

 ROUTINE:  findex

 PURPOSE:  Compute "floating point index" into a table using binary
           search.  The resulting output may be used with INTERPOLATE.

 USEAGE:   result = findex(u,v)

 INPUT:    
   u       a monitically increasing or decreasing 1-D grid
   v       a scalor, or array of values

 OUTPUT:
   result  Floating point index. Integer part of RESULT(i) gives
           the index into to U such that V(i) is between
           U(RESULT(i)) and U(RESULT(i)+1).  The fractional part
           is the weighting factor

                          V(i)-U(RESULT(i))
                          ---------------------
                     U(RESULT(i)+1)-U(RESULT(i))


 DISCUSSION: 
           This routine is used to expedite one dimensional
           interpolation on irregular 1-d grids.  Using this routine
           with INTERPOLATE is much faster then IDL's INTERPOL
           procedure because it uses a binary instead of linear
           search algorithm.  The speedup is even more dramatic when
           the same independent variable (V) and grid (U) are used
           for several dependent variable interpolations.

  
 EXAMPLE:  

; In this example I found the FINDEX + INTERPOLATE combination
; to be about 60 times faster then INTERPOL.

  u=randomu(iseed,200000) & u=u(sort(u))
  v=randomu(iseed,10)     & v=v(sort(v))
  y=randomu(iseed,200000) & y=y(sort(y))

  t=systime(1) & y1=interpolate(y,findex(u,v)) & print,systime(1)-t
  t=systime(1) & y2=interpol(y,u,v)            & print,systime(1)-t
  print,f='(3(a,10f7.4/))','findex:   ',y1,'interpol: ',y2,'diff:     ',y1-y2

 AUTHOR:   Paul Ricchiazzi                        21 Feb 97
           Institute for Computational Earth System Science
           University of California, Santa Barbara
           paul@icess.ucsb.edu

 REVISIONS:

 PROJECT:  CHIANTI

      CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
      Astrophysical Plasmas. It is a collaborative project involving the Naval
      Research Laboratory (USA), the University of Florence (Italy), the
      University of Cambridge and the Rutherford Appleton Laboratory (UK). 

 NAME

      FREEBOUND

 PURPOSE:
      Calculates the free-bound (radiative recombination) continuum.

 INPUTS

      TEMP    Temperature in K (can be an array).

      WVL     Wavelength in angstroms (can be an array).

 OUTPUTS

      INT     Free-bound continuum intensity in units of 
              10^-40 erg cm^3/s/sr/Angstrom 
              ( integral(N_H N_e dh) in cm^-5) if a DEM is not defined. 

              If DEM values are defined, it is assumed that they are given
              as N_H N_e dh/dT.  The units are 10^-40 erg/cm^2/s/srAngstrom 

              If T is given as a 1-D array, then the output will be a 
              2-D array, with one element for each temperature and 
              wavelength (but also see SUMT).

 OPTIONAL INPUTS

      DEM_INT The intensity array is multiplied by a DEM number for 
              each temperature. DEM_INT needs to be of the same size 
              as TEMPERATURE. It is needed for the synthetic spectrum 
              routines.

      IZ     Only calculate continuum for the element with atomic 
             number IZ

      ION    (To be used in conjunction with IZ.) Calculated continuum 
             for a single ion (IZ, ION).

 KEYWORDS

      NO_SETUP If the procedure setup_elements has already been called 
               then the keyword /nosetup should be set to avoid 
               repeating this step

      MIN_ABUND If set, calculates the continuum only from those 
                elements which have an abundance greater than 
                min_abund.  Can speed up the calculations.  For 
                example:
                   abundance (H)  = 1.
                   abundance (He) = 0.085
                   abundance (C)  = 3.3e-4
                   abundance (Si) = 3.3e-5
                   abundance (Fe) = 3.9e-5

      PHOTONS  The output spectrum is given in photon units rather 
               than ergs.

      SUMT     When a set of temperatures is given to FREEBOUND, the 
               default is to output INTENSITY as an array of size 
               (nwvl x nT). With this keyword set, a summation over 
               the temperatures is performed.

      VERBOSE  Output information from FREEBOUND.

 COMMON BLOCKS

      ELEMENTS

 CALLS

      FREEBOUND_ION, SETUP_ELEMENTS, READ_KLGFB, GET_IEQ

 HISTORY

      Ver.1, 24-Jul-2002, Peter Young

      Ver.2, 26-Jul-2002, Peter Young
           revised call to freebound_ion; corrected ion fraction problem

       V 3, 25-May-2005, GDZ 
                  corrected routine header.

 VERSION     :  3, 25-May-2005

 PROJECT:  CHIANTI

      CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
      Astrophysical Plasmas. It is a collaborative project involving the Naval
      Research Laboratory (USA), the University of Florence (Italy), the
      University of Cambridge and the Rutherford Appleton Laboratory (UK). 

 NAME

      FREEBOUND

 EXPLANATION

      Calculates the free-bound (radiative recombination) continuum 
      from a single ion. Note that the output does not contain the ion 
      fraction, element abundance or differential emission measure term.

 INPUTS

      TEMP    Temperature in K (can be an array).

      WVL     Wavelength in angstroms (can be an array).

      IZ      Atomic number of ion (e.g., 26 = Fe)

      ION     Spectroscopic number of ion (e.g., 13 = XIII)

 OUTPUTS

      INT     Free-bound continuum intensity. Needs to be multiplied by 
              element abundance, ion fraction and DEM to obtain the final 
              continuum intensity.

 OPTIONAL INPUTS

      IP      The ionization potential of the ion.

      VDATA   An array containing the Verner & Yakovlev data array.

      PE      An array containing the PE data from READ_FBLVL

      KLGFB   An array containing the KLGFB data from READ_FBLVL

      [Note: the above 3 inputs are used when calling freebound_ion from 
       freebound]

 KEYWORDS

      NOVERNER  If set, then the Verner & Yakovlev cross-sections will 
                not be used.

 COMMON BLOCKS

      None.

 CALLS

      READ_FBLVL, ZION2FILENAME, VERNER_XS, KARZAS_XS, CONCAT_DIR,
      READ_IP, READ_KLGFB, FILE_EXIST

 PROGRAMMING NOTES

      The way I treat the exponential function in the expression for the 
      emissivity may seem strange, but it saves a bit of time in the 
      calculation. Basically calculating exp(E-IP+E_i/T) for each level 
      was time consuming so I split it into exp(E-IP/T)*exp(E_i/T). The 
      first term comes out of the for loop, while the second term is the 
      exponential of a vector rather than an array. This made a ~30% 
      time-saving for freebound.

 HISTORY

      Ver.1, 24-Jul-2002, Peter Young

      Ver.2, 26-Jul-2002, Peter Young
          Added /noverner keyword.

      Ver.3, 30-Jul-2002, Peter Young
          Speeded up routine by modifying treatment of exponential.

 PROJECT     :  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 

 NAME

     FREEFREE

  PURPOSE:

     This routine computes the free-free continuum (bremsstrahlung) 
     using the fitting formulae of Itoh et al. (ApJS 128, 125, 2000) 
     and Sutherland (MNRAS 300, 321, 1998).

     The Itoh et al. data are valid for smaller ranges for temperature 
     and wavelength than Sutherland and so for points outside of their 
     ranges we use the data of Sutherland.

 INPUTS

    TEMP    Temperature (in K).

    WVL     Wavelengths in angstroms. Can be a scalar or vector.

 OUTPUTS

    INT     Free-free continuum intensity in units of 
            10^-40 erg cm^3/s/sr/Angstrom  
            [ integral(N_H N_e dh) in cm^-5 ] if a DEM is not defined. 

            If DEM values are defined, it is assumed that they are given
            as N_H N_e dh/dT.  The units are 10^-40 erg/cm^2/s/sr/Angstrom. 

            If T is given as a 1-D array, then the output will be a 2-D array,
            with one element for each temperature and wavelength 
            (but also see SUMT).

 OPTIONAL INPUTS

    DEM_INT An array of same length as TEMP which contains the 
            differential emission measure values at each temperature. 
            The emissivity at each temperature is multiplied by the 
            DEM value and the d(logT) value.

    MIN_ABUND This keyword allows the specification of a minimum abundance, 
              such that any elements with an abundance (relative to 
              hydrogen) less than MIN_ABUND will not be included in the 
              calculation. E.g., MIN_ABUND=1e-5.

 KEYWORDS

    NO_SETUP By default the routine asks the user which ion balance 
             and abundance files to use via pop-up widgets. If 
             /no_setup is used then this data is taken from the common 
             block.

    SUMT     The default is to output the intensity array as an array 
             of size (nwvl x nT). Setting this keyword performs a sum 
             over the temperatures to yield a vector of same size as 
             the input wavelengths, thus producing the complete 
             free-free spectrum.

    PHOTONS  Gives output emissivity in photon units rather than ergs.

 CALLS

    SUTHERLAND, ITOH

 COMMON BLOCKS

    ELEMENTS

 PROGRAMMING NOTES

    The Itoh fitting formula is only valid for (6.0 LE logT LE 8.5). 
    For temperatures below this, we thus switch to the Sutherland 
    fitting formula. There is very little (<1%) between the two at 
    logT=6.

    Itoh also has a constraint on the quantity u=hc/kTl (l=wavelength), 
    such that (-4 LE log u LE 1.0). The upper limit corresponds to the 
    continuum being cut-off prematurely at low wavelengths. E.g., for 
    T=10^6 the cutoff is at 14.39 angstroms. For these low wavelengths 
    we also use the Sutherland data to complete the continuum. Note that 
    the continuum at these wavelengths is very weak

 MODIFICATION HISTORY

    Ver.1, 5-Dec-2001, Peter Young
         Completely revised to call the separate itoh.pro and 
         sutherland.pro routines.

    V. 2, 21-May-2002,  Giulio Del Zanna (GDZ),
          Corrected the description of the  units.
          Added verbose keyword and a printout.

    V. 3, 22-May-2002,  Peter Young (PRY)
          Added MIN_ABUND optional input.
          Changed ioneq_t to ioneq_logt (GDZ).

       V 4, 25-May-2005, GDZ 
                  corrected routine header.

 VERSION     :  4, 25-May-2005

 PROJECT:  CHIANTI

       CHIANTI is an atomic database package for the calculation of
       continuum and emission line spectra from astrophysical plasmas. It is a 
       collaborative project involving the Naval Research Laboratory
       (Washington DC, USA), the Arcetri Observatory (Firenze, Italy), and the
       Cambridge University (United Kingdom).


 NAME:
	GET_ATOMIC_WEIGHT


 PURPOSE:

       to produce  an atomic weight. 

 PROCEDURE:


 This routine converts the ion atomic number into an atomic weight. Where 
 an element has more than one isotope, the weight is that of the most 
 common.

 I've written this routine in order to apply a thermal broadening to 
 lines in a CHIANTI synthetic spectrum (see routine make_chianti_spec.pro).


 CALLING SEQUENCE:

       IDL>

 EXAMPLES:

 INPUTS:
        IZ 

 OPT. INPUTS :

 OUTPUTS:
       the atomic weight

 OPTIONAL OUTPUTS:

 KEYWORDS:

 CALLS: 

 COMMON:

 RESTRICTIONS:
            I go up to zinc (iz=30)


 SIDE EFFECTS:

 CATEGORY:
	
	synthetic spectra


 PREV. HIST. :

 WRITTEN     : 
       Ver.1, 22-Jun-00, Peter Young (PRY)

 MODIFICATION HISTORY:

  VERSION     : V 1, 22-Jun-00, Peter Young (PRY)

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 

     		          
 Purpose     : calculates the contribution functions G(T) at constant 
		pressure or density  of the lines present in the CHIANTI
		database, corresponding to  a given set of observed lines.

 Category    :
               
 Explanation : This routine is called by CHIANTI_DEM. It cannot be used as
		a stand-alone routine.
		The observation file is read by CHIANTI_DEM.
		GET_CONTRIBUTIONS starts reading 
		the ionization equilibrium file and the masterlist of the
		ions present in the CHIANTI database.
		GET_CONTRIBUTIONS  then searches the 
		CHIANTI database (ion per ion) for all the 
		theoretical lines corresponding to the observed	lines, i.e. 
		that lie in a OBS_WVL(i) +/- DELTA_LAMBDA_OBS(i) interval
		centered on the observed wavelength OBS_WVL(i).
		Then calculates the G(T) values for the temperature interval
		log(T)= 4.0 - 8.0  with steps of log(T) = 0.1
		A constant pressure OR a constant density for all the lines
 		is used. If you select a constant pressure,
               for each ion the contribution function is calculated at an 
               electron density N_e equal to the ratio of the pressure 
               and the temperature of maximum ionization fraction:  
               C=C( T, N_e = P/T_ion)
               The C(T) values are stored by GET_CONTRIBUTIONS in the output 
		file OUTPUT.CONTRIBUTIONS.

		In the case no theoretical lines corresponding to an observed
		line are found, the routine writes the wavelength of the line
		to be excluded from the fit in the array EXCLU_OBS_WVL_NO_TEO;
		these lines are then excluded from the fitting  by 
	 	CHIANTI_DEM. You might consider the possibility to start again
		incrementing the DELTA_LAMBDA_OBS, to see if there are 
		theoretical lines in the vicinity.


 Use         : called by CHIANTI_DEM to calculate the contribution functions

 Examples    : 

    
 Inputs      :	Various, in form of keywords.
               
               
 Opt. Inputs : none
               
 Outputs     : OUTPUT.CONTRIBUTIONS  
		Is the file where all the contribution  functions G(T) are 
		stored. In the first two lines  the ionization equilibrium 
		file name, and the constant value of pressure or density 
		adopted are reported. Then for each line you have reported  
               the observed wavelength, the theoretical one, the element and
		ionization stage, then the C(T) values. At the end the 
		specification for each transition.


 Opt. Outputs: None
               
 Keywords    : (all passed by CHIANTI_DEM)


	CUT_GT:			if set, only those
				theoretical lines that have a MAX(G(T)) greater
      			        than the value set, are kept; it is useful to 
				set this value in order to reduce the number 
				of lines in the file where the G(T) are stored.

	DENSITY : 		the value of the density (Ne).

	FILE_INPUT:		if set, you are not 
				requested to select the observation file.

  
	N_MATCHES:              
		In the unlikely event that more than 20 (default value for 
		N_MATCHES) theoretical lines corresponding to an observed
		line are found, the routine stops; in this case, you have to 
		start again setting N_MATCHES equal to a greater number. 

	PRESSURE:     		the value of the pressure (Ne T)

	OUTPUT  :  	-the core name for the output


 Calls       : 
		READ_IONEQ 
               read_masterlist
		CONVERTNAME
               ion2spectroscopic
		ZION2FILENAME
		READ_WGFA2
		READ_SPLUPS
		POP_SOLVER
		READ_ELVLC
		READ_IONREC
		CONVERT_TERMS

 Common      : elvlc                          - energy levels
               wgfa                           - radiative data
               upsilon                        - upsilon data
		      
		obs, 	obs_int,obs_sig,n_obs
		obs_o,	obs_wvl,obs_id,obs_delta_lambda
 		dem, 	d_dem_temp,dem_temp,log_dem_temp,log_t_mesh,log_dem_mesh
		contr,	ch_tot_contr
		ab,	abund_name,abund_info,xuvtop,ioneq_name

		these are the commons with GET_CONTRIBUTIONS.PRO:

		various,	exclu_obs_wvl_no_teo,const_net,$
		 dem_temp_min,dem_temp_max,n_dem_temp,$
		 ch_wvl,ch_l1,ch_l2,ch_id,ch_z,ch_ion,ch_contr_wa,$
		 ch_pop,ch_contr_list, ch_term,ch_n_contr


 Restrictions: ;
		THIS IS NOT A STAND-ALONE PROCEDURE. 
		It is called by CHIANTI_DEM,
		and has a lot of common blocks with other procedures.

		In the unlikely event that more than 20 (default value for 
		N_MATCHES) theoretical lines corresponding to an observed
		line are found, the routine stops; in this case, you have to 
		start again setting N_MATCHES equal to a greater number. 

		Of course you need to have the enviroment variable CDS_SS_DERE
		pointing to the CHIANTI database top directory.

               
 Side effects: None known.
               
 Category    : spectrum
               
 Prev. Hist. :
       Written by Ken Dere (NRL) as part of the CHIANTI package 
       in collaboration with Brunella Monsignori Fossi, Enrico Landi
       (Arcetri Observatory, Florence), Helen Mason and Peter Young
       (DAMTP, Cambridge Univ.). Incorporated into the CDS software.  
 Written     : 
       Version 1, Giulio Del Zanna (GDZ)  5 November  1997 
	UCLAN (University of Central Lancashire, UK) 

 Modified    :  
       Version 2, 31-Oct-2000, GDZ, DAMTP.  Rewritten completely the routine,
       to make it compatible with CHIANTI v.3. Based the core calculations on
       new implementations due to Peter Young, CfA. 

       Version 3, 5-Dec-2000, GDZ, DAMTP. Fixed a bug when checking the 
       values in the .splups files.


       Ver. 4,  25-Apr-02, GDZ  
              Revised to account for v.4 variations. By default the proton
              rates are included in the calculation of the level population.

       V.5, Giulio Del Zanna (GDZ)
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

       V. 6,  10-July-2002  GDZ
                  Corrected a bug. It now properly includes by default the
                  proton rates in the population solver. 

       V. 7,  4-Oct-2003, GDZ
                  modified the input to POP_SOLVER, now it is dealt with an
                  input structure. 

       V. 8, 3-Nov-03  GDZ
                  Modified format e8.2 to e9.2 for Windows compatibility.

       V. 9, 4-May-05 Enrico Landi (EL)
                  Modified in order to include ionization and recombination
                  data in the input to POP_SOLVER

 VERSION     :     9, 4-May-05

 PROJECT:  CHIANTI

      CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
      Astrophysical Plasmas. It is a collaborative project involving the Naval
      Research Laboratory (USA), the University of Florence (Italy), the
      University of Cambridge and the Rutherford Appleton Laboratory (UK). 

 NAME

      GET_IEQ()

 EXPLANATION

      For a specified ion (IZ, ION) and set of temperatures (TEMP) this 
      routine takes the ion fraction values tabulated in one of the CHIANTI 
      .IONEQ files, interpolates and extracts the values of the ion 
      fraction at the input temperatures.

 INPUTS

      TEMP   The temperature(s) at which the ion fractions are required.

      IZ     The atomic number of the element (e.g., 26 = iron).

      ION    The spectroscopic number of the ion (e.g., 13 = XIII).

 OPTIONAL INPUTS

      IONEQ_LOGT  The temperature output from the READ_IONEQ routine.

      IONEQ_FRAC  The ion fractions from the READ_IONEQ routine.

 OUTPUT

      A vector of same length as the input TEMP containing the ion 
      fractions at these temperatures.

 CALLS

      READ_IONEQ

 HISTORY

      Ver.1, 24-Jul-2002, Peter Young

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	GOFNT

 PURPOSE:

	calculate G(n,T) function (line intensity per unit emission measure)
       
 PROCEDURE:

	Must specify line to form numerator and denominator
       Multiple lines can be selected and summed
       This can now be done interactively or not.

 CALLING SEQUENCE: 

	GOFNT,Ion,Wmin,Wmax,Temperature,G,Desc,density=


 INPUTS:

       Ion:   the CHIANTI style name of the ion, i.e., 'c_5' for C V

       Wmin:  minimum of wavelength wavelength range of interest in Angstroms

       Wmax:  maximum of wavelength wavelength range of interest

 OPTIONAL INPUTS:

       Many - see the keywords below.

 OUTPUTS:

	Temperature:  an array of temperatures 

       G:  Intensity  per unit emission measure N_e*N_H*dh [cm^-5].
           The resulting units are therefore erg cm^+3 s^-1 sr-1

           C(T)= 1/(4*!pi)* A_ji*(N_j(X^+m)/N(X^+m))*(N(X^+m)/N(X))*(N(X)/N(H))/N_e

            unless  /NOABUND is set, in which case 
           C(T)= 1/(4*!pi)* A_ji*(N_j(X^+m)/N(X^+m))*(N(X^+m)/N(X))/N_e

           G(T)=(hc/lambda_ij)*C(T) 
           G(T)= C(T)   if /PHOTONS is set

       Desc:  a short string description of the selected line


 OPTIONAL OUTPUTS:

	Postscript file withthe plot of G(T).

       Ascii file with the values of G(T). 
        
       VALUE      The array of G(T) values corresponding to logt0.


 KEYWORD PARAMETERS:


	PRESSURE:  specifies the pressure in units of NeT (cm^-3 K).  G is then
                  calculated at that constant pressure 
		
	DENSITY:  specifies the electron density in units of cm^-3.  G is then 
                 calculated at that value of the electron density.  If neither the 
                 density or pressure keywords are specified, a constant
                  density of 1.e+10 cm^-3 is assumed

       PHOTONS:  sets output in photons/s

       RPHOT   Distance from the centre of the star in stellar radius units.
               I.e., RPHOT=1 corresponds to the star's surface. (Default is
               infinity, i.e., no photoexcitation.)

       RADTEMP The blackbody radiation field temperature (default 6000 K).

       OUTFILE:  the (optional) name of the output ascii file where a 
                   listing of the line ratio intensity as a function of 
                   temperature is saved.

       PSFILE:  the (optional) name of the output postscript file 
                  where a plot of the chosen G(T) is saved.

       NOABUND: If set, the G(T)'s are not multiplied by the abundance 
                factor.

       NOPROT   If set, then proton rates are not included.


	ABUND_NAME:  Name of the abundance file to use.  If not passed, then
		     the user is prompted for it.

	IONEQ_NAME:  Name of the ionization equilization name to use.  If not
		     passed, then the user is prompted for it.

       ALL          If set, all lines are calculated, including
                    the 'unobserved' ones. 

       LOWER_LEVELS
       UPPER_LEVELS
                    Arrays with the indices of the lower and upper levels
                    pertaining to the transitions you want to get. 
                    If more than one couple is given, the G(T) of the 
                    lines are summed.
                    Obviously, the given indices must correspond to transitions
                    that are present in the database.

       ARCSECS  
                 If set, units are photons (ergs) cm^+3 s^-1 arcsecs^-2

       VERBOSE

       LOGT0       An array of log T values for which the G(T) are wanted.
       VALUE       The array of G(T) values corresponding to logt0.
 
                   If logt0 is defined, and within the limits of the 
                   temperatures for which G(T) NE 0, the array VALUE
                   is returned with a simple spline interpolation.

 CALLS:

       CH_SYNTHETIC, CH_XMENU_SEL

 COMMON BLOCKS: None

 RESTRICTIONS:

 SIDE EFFECTS:

 EXAMPLE:

      IDL> gofnt,'o_5',1000.,1500.,temp,goft,desc,density=1.e+16


 CATEGORY:

	spectral diagnostics


 MODIFICATION HISTORY:

 	Written by:	Ken Dere
	October 4, 1996:     Version 1
       14-Jul-2000     Peter Young, now calls pop_solver

       26-Oct-2000 GDZ, added keyword NOABUND to not multiply for the abundence
       factor. Corrected header for a wrong description.

	Version 4, 21-Dec-2000, William Thompson, GSFC
		Modified for better cross-platform graphics capability

  
       Version 5, 8-Nov-01, Giulio Del Zanna (GDZ). 

       Rewritten as a wrapper routine using the new procedures.
           Corrected a few inconsistencies in the plots.

       Version 6, 18-Nov-01, Peter Young
           Added /noprot, rphot and radtemp keywords.

       Version 7, 11-Dec-01, Peter Young
           Changed call to ch_strpad to strpad.

       V. 8, GDZ, 28-Apr-02 Added abund_name,ioneq_name keywords.
       v. 9  21-May-2002, GDZ
             generalized directory concatenation to work for
             Unix, Windows  and VMS. 

       V.10, 15-Aug-02, GDZ 
              Major revision:
              -Removed the call to ch_xselect_s, that did not work for long lists.
              -Added a '*' in the line lists, to identify 'unobserved' lines.
              -Replaced the commands to create PS file, to make it
               cross-platform compatible.
              -Added a large number of cosmetics, mainly lables to the axes and
               titles.
              -Added keyword ALL. If set, all lines are calculated, including
              the 'unobserved' ones. 
              -Added the CHIANTI version number in the outputs.

       V. 11, 19-Sep-02, GDZ
              Clarified output units.

       V.12, 25-Jun-03, GDZ, 
              Added many new keywords. Now is possible to use the routine 
              with background jobs, in not-interactive mode.
              Rounded the wavelengths. 

       V.13, 24-Sept-2003, GDZ 
              Corrected a bug when logt0 is not defined.

       V.14, 3-Nov-03  GDZ
             Modified format e8.2 to e9.2 for Windows compatibility.

 VERSION     :   14, 3-Nov-03 

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME: G_OF_T()
       
 PURPOSE:

	To compute DE * F(T) * n_j * A_ji / N_e for selected emission lines. 
	Option to also multiply by abundance.

 CATEGORY:

       Atomic data analysis

 EXPLANATION:

	The G-of-T function has a number of different definitions in the 
	literature. In the most basic form it contains only the temperature 
	dependent parts (i.e., 0.83*n_j*A_ji*F(T)/N_e), but often a Delta-E 
	and Ab(X) are added as well. Here, the _default_ form is:

	Delta-E * 0.83 * n_j * A_ji * F(T) / N_e

	By using the NO_DE keyword, the Delta-E can be omitted, while the 
	ABUND keyword allows the abundance to be added.

	The function that is output is tabulated over 4.0 <= logT <= 8.0 
	in 0.1 dex intervals. If you want the function tabulated over 
	smaller intervals, run the ION_INTERP routine afterwards.

 CALLING SEQUENCE:


 EXAMPLES:

	RESULT=G_OF_T(26,13)

	RESULT=G_OF_T(26,13,DENS=7)

	RESULT=G_OF_T(26,13,GOFTFILE='my_gofts.dat')

       RESULT=G_OF_T(26,13,/ABUND)

       RESULT=G_OF_T(26,13,ABUND_FILE=ABUND_FILE, IONEQ_FILE=IONEQ_FILE)

 INPUTS:

	IZ:	The atomic number of the ion (e.g., 26 = Fe)

	ION:	The spectroscopic number of the ion (e.g., 12 = XII)

 OPTIONAL INPUTS:

	DENS:	The logarithm (to base 10) of the density at which the 
		emissivities are calculated (default=10.)

	WRANGE: Wavelength range from which lines are required. If not 
		specified, then the 10 strongest lines are displayed.

	PATH:	If specified, the routine will look for the atomic data in 
		the PATH directory, rather than in the CHIANTI database

	GOFTFILE:	By specifying GOFTFILE as a filename, the G-of-T 
			function can be stored in this file. It is stored 
		in the form a structure (called goft_list) with the following 
		labels:

	  goft_list.label: user-specified string, e.g., 'Si XII  520.7'
	  goft_list.func:	 fltarr(41), the G-of-T function

	If the same GOFTFILE is specified for another ion, then the 
	G-of-T function is added to the existing structure. The GOFTFILE 
	option only works when the ABUND keyword is set. The GOFTFILE is 
	meant to be read by another routine called GOFT_PLOTTER.

	INDEX:	Allows the direct specification of indices within the 
		emiss structure. This allows the g_of_t routine to be 
		run without the menu widget appearing. If the /quiet 
		keyword is also used, then the routine will run "silently".

	RADTEMP	Specify background radiation temperature (default: 6000 K)

	RPHOT   Distance from the centre of the star in stellar radius units.
               I.e., RPHOT=1 corresponds to the star's surface. (Default is
               infinity, i.e., no photoexcitation.)

       IONEQ_FILE  Directly specify the name of the ion balance file 
               (including directory path). If not set, then a widget will 
               pop up allowing you to select a file.

       ABUND_FILE  Directly specify the name of the abundance file 
               (including directory path). One can also use /ABUND_FILE 
               to include the abundances in the G(T) function, but allow 
               the abundance file to be picked through a widget.

 KEYWORDS:

       NOPROT  If set, then the default setting will be NOT to use 
               proton rates. This can be changed within the routine.

	NO_DE:	If set, then the output function will *not* contain the 
		Delta-E. Be careful using this if you are using blends 
		(as Delta-E is different for different wavelengths).

	QUIET	If set, then don't plot the G(T) function or print out 
               information to the screen.

 CALLS:

	EMISS_CALC, READ_IONEQ, READ_ABUND, EMISS_SELECT, CH_GET_FILE

 RESTRICTIONS:


 HISTORY:

	Ver.1, PRY 28-Jul-97.
	Ver.2, PRY 22-Jun-98, added CHOOSE keyword and removed RAY
	Ver.3, PRY 4-Aug-98, cosmetic changes following comments of Giulio 
			Del Zanna
	Ver.4, PRY 5-Sep-98, added call to choose_ioneq
	Ver.5, PRY 23-Sep-98, added GOFTFILE input
	Ver.6, PRY 3-Mar-99, now calls EMISS_SELECT
       Ver.7, PRY 6-Nov-00, removed the /CHOOSE keyword; also changed 
                       PICKFILE call to DIALOG_PICKFILE and removed call 
                       to the CHIANTI routine ADD\_SUBDIR
       Ver.8, PRY 18-Oct-01, adjusted for proton rates, and 
                       photoexcitation.
       Ver.9, PRY 9-Dec-01, completed modifications for v.4 of CHIANTI.

       V.  10, 21-May-2002, Giulio Del Zanna (GDZ) 
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS.
       Ver. 11, 9-Feb-2005, Peter Young
                   changed keyword_set(abund) to keyword_set(abund_file)

 VERSION     :   11, 9-Feb-2005

function	hastogram
	returns a frequency histogram over a specified grid,
	calculated in a fast and clever way.  really.
	works in haste, without waste.

syntax
	f=hastogram(list,x,wts=wts)

parameters
	list	[INPUT; required] list of numbers to bin
	x	[I/O] the required binning scheme
		1: if not set, assumes a linear grid of size 100 from
		   min(LIST) to max(LIST)
		2: if scalar or 1-element vector, assumes this to be the
		   number of bins
		   * if -ve, log grid, else linear
		3: if vector with more than 1 element, assumes it to be
		   all the bin-beginning values and the final bin-ending
		   value.
		*  overwrites variable by adopted grid

keywords
	wts	[INPUT] if given, appropriately weights each element of LIST
		* default is unity
		* if size does not match size(LIST), will be appropriately
		  interpolated
	_extra	[JUNK] here only to prevent crashing the program

description
	the problem is the following: if the number of bins is large,
	accumulating a frequency histogram by linear search takes too
	long, esp. in IDL if one uses for-loops.
	so, first create a monster array containing both the list elements
	and the grid values.  then sort this array.  this results in an
	array where the list elements are all nicely placed within the
	correct bins.  now, if we've been keeping track of the positions
	of the list elements, it's an easy job to count up the number in
	each bin of the grid.  to do the latter, we first create a new
	array made up of -1s in positions of list elements and position
	indices for grid values and reorder according to the above sort.
	then, replace each -1 by the nearest non-(-1) from the left.  now
	each list element is assigned the correct bin number.  voila!

restrictions
	X must be sorted in increasing order.

subroutines


history
	vinay kashyap (Jan98)  PINT_of_ALE
	added kludge to speed up in case max(X) < max(LIST) (VK; Sep98)
	added quit in case X is not sorted in ascending order (VK; JanMMI)

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME: INTEGRAL_CALC
       
 PURPOSE:

       To compute the atomic data integral for use in column or volume
	emission measure work.

 CATEGORY:

       Scientific analysis

 EXPLANATION:

 	Defining

	G(T) = 0.83 * Fr(T) * N_j * A_ji / N_e

	where Fr(T) is the ionisation fraction (e.g., from Arnaud & 
	Rothenflug), N_j the relative population of level j, A_ji the 
	A-value for the j->i transition and N_e the electron density. The 
	0.83 is the ratio of hydrogen to free electrons, which is constant 
	above around 10^4 K. This function is sharply-peaked at a 
	temperature T_mem (the temperature of maximum emission, which can 
	be different from the temperature of maximum ionisation, T_max) 
	and so an oft-used approximation is to take G(T) constant in the 
	range log T_mem - 0.15 to log T_mem + 0.15 and zero outside. The 
	value of the constant, which we call C_lambda here, is then given 
	by

	C_lambda =    integral { G(T) dT }
                     --------------------
                  T_mem * (10^0.15 - 10^-0.15)

	If EM(s) is the column emission measure, F the flux (erg cm-2 s-1)
	in a line lambda, Ab the abundance of the element and DE (erg) the
	energy for the transition, then:

	F = DE * Ab * C_lambda * EM(s)

	If we are dealing with intensities I (erg cm-2 s-1 sr-1) then:

	4pi * I = DE * Ab * C_lambda * EM(s)

	This program extracts the ionisation balance and emissivities from 
	the CHIANTI database and calculates C_lambda for all lines in the 
	specified wavelength interval WRANGE by integrating over 
	0.02 dex temperature intervals, using the IDL INT_TABULATED function.

	The C_lambda functions for all the lines in the selected wavelength 
	range WRANGE are displayed as well as the temperature of maximum 
	emission (T_mem), DE*C_lambda and 4pi/(DE*C_lambda). These latter 
	two quantities are useful for the emission measure analysis.

	Any combination of the displayed lines can then be blended and the 
	corresponding quantities for the blend will be displayed.

	The function Fr(T) * N_j * A_ji can also be plotted at this stage.

 CALLING SEQUENCE:

       INTEGRAL_CALC, IZ, ION, [WRANGE=WRANGE, /CHOOSE, DENS=DENS]

 EXAMPLES:

	INTEGRAL_CALC, 26, 13, WRANGE=[200,205], /CHOOSE

	INTEGRAL_CALC, 14, 10, WRANGE=[250,270], DENS=10.

 INPUTS:

	IZ:	The atomic number of the ion
	ION:	The spectroscopic number of the ion (e.g., 12 = XII)

 OPTIONAL INPUTS:

	DENS:	The density at which the emissivities are calculated 
		(default=10.)
	WRANGE: Wavelength range for which C_lambda functions are 
		calculated. If not given, then the 10 strongest lines 
		are printed.
	INDEX:	Particular elements in the emissivity structure can be 
		selected with INDEX. This allows integral_calc to be run 
		'silently'. The output is contained in the OUTSTR structure. 
		If index is given as, e.g., [7,8], then the C_lambda 
		functions for these two lines are summed and output.
	PATH:	Directly specify the directory path where the Chianti data 
		for the ion is found

       ABUND_FILE  The name of a CHIANTI abundance file. This is used for 
               calculating the proton to electron ratio. Default is 
               !abund_file.

       IONEQ_FILE  The name of a CHIANTI ion balance file. This is used for 
               calculating the proton to electron ratio and evaluating 
               the T_max of the ion. Default is !ioneq_file.

       RADTEMP  The blackbody radiation field temperature (default 
                6000 K).

       RPHOT    Distance from the centre of the star in stellar radius 
                units. I.e., RPHOT=1 corresponds to the star's surface. 
                (Default is infinity, i.e., no photoexcitation.)

 KEYWORDS:

	CHOOSE:	Allow ion balance calculations to be selected manually 
		(see choose_ioneq.pro routine).

 OPTIONAL OUTPUTS:

	OUTSTR:	A structure with the following tags

		.tmem	- the T_mem for the line(s)
		.dec	- total( de * c_lambda )
		.pidec	- 4 * pi / total( de * c_lambda )

	Only output when INDEX is specified.

 COMMON BLOCKS:

	None.

 CALLS:

	EMISS_CALC, CH_GET_FILE, READ_IONEQ

 HISTORY:

	Ver.1: PRY, 28-JUN-97.
	Ver.2: PRY, 7-OCT-97. Added TEMPI and GOFT, for plotting.
	Ver.3: PRY, 31-JUL-98. Added PATH.
	Ver.4: PRY, 6-APR-99. Added INDEX, OUTSTR. Removed TEMPI and GOFT 
		(these can be got from the g_of_t routine).
       Ver.5: PRY, 9-Dec-01. Modified for v.4 of CHIANTI.

       V.6, 21-May-2002, Giulio Del Zanna (GDZ) 
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

       V.7, 06-Aug-02 GDZ
              Changed the use of CHIANTI system variables. 
       

 VERSION     :   7, 06-Aug-02 

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 

 NAME:
	ion2filename

 PURPOSE:
	Ion names as character strings are converted to
	provide their complete file name (with out suffix)

 CATEGORY:
	
	naming utility

 CALLING SEQUENCE:

       ION@FILENAME,Ion,Filename


 INPUTS:
	Name:   such as 'c_2'


 OUTPUTS:

	Filename:  !xuvtop/c/c_2/c_2


 EXAMPLE:

                     > ion2filename,'c_2d',filename
                     > print,filename
                     > !xuvtop/c/c_2d/c_2d

 MODIFICATION HISTORY:

 	Written by:	Ken Dere

	V.2,  September 1999:  added for use with Version 3

       V.3, 21-May-2002, Giulio Del Zanna (GDZ) 
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

 VERSION     :   3, 21-May-2002 

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	ION2SPECTROSCOPIC

 PURPOSE:

	provide identification string

 CATEGORY:

	database.

 CALLING SEQUENCE:

       ION2SPECTROSCOPIC, Ion, Spectroscopic

 INPUTS:

       Ion:   CHIANTI notation for an ion, i.e., 'c_2' for C II	

 OUTPUTS:

	Name:  the spectroscopic notation for the ion, i.e. 'C II'

 EXAMPLE:
             > ion2spectroscopic,'fe_13',name
             > print,name
             > Fe XIII   

             > ion2spectroscopic,'o_6d',name
             > print,name
             > O VI d   

 MODIFICATION HISTORY:
 	Written by:	    Ken Dere
	September 1999:     Version 3.0

       Ver.2, 11-Dec-2001, Peter Young
           Revised routine; removed call to repstr

       V.3, 29-May-2002, Giulio Del Zanna (GDZ) 
              Added output keyword dielectronic.

       V.4, 12-Aug-02, GDZ 
           Corrected a typo concerning XXII.

 VERSION     :   4, 12-Aug-02

 NAME

   ION_FRAC_INTERP

 PROJECT

   CHIANTI

 EXPLANATION

   Performs interpolation of an ion fraction array (such as contained in
   the CHIANTI .ioneq files) to yield ion fractions at temperatures TEMP.

   Note that the ion must already have been selected before calling this
   routine, since IONEQ_FRAC is a 1D array. The routine GET_IEQ is an
   alternative if the ion has not been selected.

 INPUTS

   TEMP        Temperature(s) for which ion fractions are required. 
               Units: K.

   IONEQ_LOGT  Log (base 10) of temperature (units: K). A 1D array of
               temperatures for which the ion fraction is defined.

   IONEQ_FRAC  A 1D array of ion fractions at the temperatures defined by
               ioneq_logt

 OUTPUT

   The ion fraction defined at the temperatures TEMP. If values of TEMP lie
   outside the range of the ion fraction or the range of IONEQ_LOGT, then
   values of 0 are returned at these temperatures.

 HISTORY

   Ver.1, 10-Jun-2005, Peter Young

 EXPLANATION:

	When accessing ionisation balance data from the CHIANTI database, it 
	is output at log temperature values from 4 to 8 at 0.1 intervals. 
	For display purposes it is often nice to perform spline interpolation 
	to give a smoother function. This interpolation should be performed 
	on the logarithm of the data as this is more slowly varying.

	This routine performs such an interpolation. It is only essential to 
	input G_T and N. Specifying T is optional (see below), while TI and 
	G_TI are output. N gives the number of points within an interval over 
	which interpolation is performed.

 INPUTS:

	G_T:	Data for which interpolation required

 OPTIONAL INPUTS:

	T:	Values at which is G_T is tabulated. If not specified, then 
		taken as 4 to 8 in 0.1 intervals.
	N:	Specifies `smoothness' of fit. E.g., N=5 means that single 
		intervals are divided into 5 intervals.
	TI:	If some temperatures are specified, then the SPLINE call is 
		used to work out the values of G_TI that correspond to these 
		temperatures. Only works if N is not specified.

 OUTPUTS

	T:	If not specified, then output as an array from 4 to 8 in 0.1 
		intervals
	TI:	Interpolated T values. If the TI are specified on the command 
		line, then these values are returned. 
	G_TI:	Interpolated G_T values

 KEYWORDS

	PLOT -	The interpolated data is displayed together with the original 
		data.

 EXAMPLE:

	g_t=g_of_t(26,13,/ray)
	ion_interp,t,g_t,ti,g_ti,5,/plot
	plot,t,g_t,psym=2,xra=[5.8,6.7]
	oplot,ti,g_ti

	ion_interp,t,g_t,[6.112,6.254],g_ti,/plot

 CALLS:

	SPLINE

 HISTORY:

	Ver 1, PRY 17-JUN-98
	Ver 2, PRY 10-AUG-98, corrected minor bug
	Ver 3, PRY 22-SEP-98, corrected interpolation error
	Ver 4, PRY 3-MAR-99,  now allows TI to be specified

 CONTACT:

	Peter Young, Cambridge University (P.R.Young@damtp.cam.ac.uk)

 NAME

       ISOTHERMAL

 PURPOSE:
       Computes spectra from isothermal plasmas. A number of isothermal 
       plasmas can be included.
       Note that this routine has a number of unique features that 
       distinguish it from the other CHIANTI synthetic spectra routines. 
       See the Programming Notes section.

 INPUTS:

       WMIN      Minimum of desired wavelength range in Angstroms.

       WMAX      Maximum of desired wavelength range in Angstroms.

       WAVESTEP  Bin size of spectrum (in Angstroms)

       TEMP      Electron temperature (or array).

 OPTIONAL INPUTS

       PRESSURE  Electron pressure in units of cm^-3 K.

       EDENSITY  Electron density in units of cm^-3.

       EM        Emission measure. The units of EM govern the intensity 
                 units of the emission lines (i.e., column or volume 
                 emission measure units). If EM is not specified, then the 
                 emission measure is set to (N_e * N_H) where N_e is 
                 derived from the user-specified PRESSURE or EDENSITY, 
                 and N_H is derived from the routine PROTON_DENS.PRO.

       SNGL_ION  Rather than include the entire list of CHIANTI ions in 
                 the calculation, this input can be used to select a 
                 single ion, or a number of different ions. E.g., 
                 SNGL_ION='s_2' or SNGL_ION=['s_2','s_3','s_4'].

       RADTEMP   The blackbody radiation field temperature (default 6000 K).

       RPHOT    Distance from the centre of the star in stellar radius units.
                I.e., RPHOT=1 corresponds to the star's surface. (Default is
                infinity, i.e., no photoexcitation.)

       MASTERLIST  The list of ions that will be considered for the 
                   spectrum is contained in the masterlist file in the 
                   CHIANTI directories. The user can specify his own file 
                   through this keyword. E.g., 
                   masterlist='/user/home/masterlist.ions'


	ABUND_NAME:  Name of the abundance file to use.  If not passed, then
		     the user is prompted for it.

	IONEQ_NAME:  Name of the ionization equilization name to use.  If not
		     passed, then the user is prompted for it.


  KEYWORDS

       NOPROT     Switch off the inclusion of proton rates in the level 
                  balance.

       ERGS       The units of the output spectrum are by default in photons. 
                  Setting /ERGS switches to erg units.

       CONT       Adds continuum (free-free, free-bound, two-photon) to 
                  spectrum.

  OUTPUTS:

        LAMBDA   Wavelength array of calculated synthetic spectrum.

        SPECTRUM Intensity array. The units depend on the user inputs to 
                 ISOTHERMAL -- see note below. 

        LIST_WVL A list of wavelengths for use with synthetic_plot.pro

        LIST_IDENT A list of line identifications for use with 
                   synthetic_plot.pro

 PROGRAMMING NOTES

        Intensity Units
        ---------------
        The units are of the form photons cm^3 s^-1 sr^-1 * (units of EM), 
        changing to ergs if the /ergs keyword is set.

        The volume emission measure (N_e*N_H*V) has units cm^-3.

        The column emission measure (N_e*N_H*h) has units cm^-5.


        Unique features
        ---------------
        The emission lines in the final spectrum have no width and thus 
        each occupies a single pixel of the spectrum. The size of the 
        pixels are set by WAVESTEP.

        As stated above, the units of the output spectrum are 
        photons cm^3 s^-1 sr^-1, i.e., there is no "per angstrom" term. 
        This means that (i) the height of the emission lines in the 
        spectrum does not change with varying WAVESTEP, and (ii) the height
        of continuum does change with WAVESTEP.

 COMMON BLOCKS

        ELEMENTS

 CALLS

        CH_SYNTHETIC, READ_ABUND, CH_GET_FILE, CONCAT_DIR, FREEFREE, 
        FREEBOUND, TWO_PHOTON

 HISTORY
        Ver.1, 8-Apr-02, Peter Young  Rutherford Appleton Laboratory,
        p.r.young@rl.ac.uk 
        Tries to replicate the behaviour of the original ISOTHERMAL which 
        was found in earlier versions of CHIANTI (v.3 and earlier). 

 MODIFICATION HISTORY

       Ver. 2, Giulio Del Zanna (GDZ), 28-Apr-02 
               Added abund_name,ioneq_name keywords.
               Also, added photons keyword in call to MAKE_CHIANTI_SPEC.

       Ver. 3, Peter Young, 24-May-02
                 Modified to produce arrays of spectra when an array of 
                 temperatures is given

       V.4, GDZ, 28-May-02 
              Added a couple of checks on file existence and modified the call
              to ch_synthetic and make_chianti_spec  due to change of keyword
              names.  

       V.5, Peter Young, 16-Jul-02
              Restructured routine to avoid crashes when a large number of 
              temperatures is input.

       V.6, 8-Aug-02 GDZ
              Added one error checking

       V.7, 18-Aug-03, Peter Young
              Added EM= keyword.


 VERSION     : 
       Version 6, 8-Aug-02 
        

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 

 NAME

    ITOH

 EXPLANATION

    Calculates the relativistic free-free continuum using the fitting 
    formula of Itoh et al. (ApJS 128, 125, 2000).

 INPUTS

    TEMP    Temperature (in K).

    WVL     Wavelengths in angstroms. Can be a scalar or vector.

 OUTPUTS

    INT     Free-free continuum emissivity in units of 
            10^-40 erg cm^3 / s / sr / Angstrom per unit emission 
            measure [ integral(N_e N_H dh) in cm^-5 ]. If T is given as 
            a 1-D array, then RAD will be output as a 2-D array, 
            with one element for each temperature and wavelength 
            (but also see SUMT).

 OPTIONAL INPUTS

    DEM_INT An array of same length as TEMP which contains the 
            differential emission measure values at each temperature. 
            The emissivity at each temperature is multiplied by the 
            DEM value and the d(logT) value.

    MIN_ABUND This keyword allows the specification of a minimum abundance, 
              such that any elements with an abundance (relative to 
              hydrogen) less than MIN_ABUND will not be included in the 
              calculation. E.g., MIN_ABUND=1e-5.

 KEYWORDS

    NO_SETUP By default the routine asks the user which ion balance 
             and abundance files to use via pop-up widgets. If 
             /no_setup is used then this data is taken from the common 
             block.

    SUMT     The default is to output the intensity array as an array 
             of size (nwvl x nT). Setting this keyword performs a sum 
             over the temperatures to yield a vector of same size as 
             the input wavelengths, thus producing the complete 
             free-free spectrum.

    PHOTONS  Gives output emissivity in photon units rather than ergs.

 CALLS

    Chianti:  SETUP_ELEMENTS

 PROGRAMMING NOTES

    In the Itoh et al. paper they state that their fitting formula is 
    valid for ion charges (Z_j) of 1-28. The data-file they provide 
    actually goes up to Z_j=30, and so you will see that the loop over 
    z (see below) goes up to 30.

    There is no restriction on the elements for which the fitting 
    formula is valid, and so all elements are allowed to be included 
    (subject to their abundances being non-zero).

 HISTORY

    Ver.1, 3-Dec-2001, Peter Young

    Ver.2, 22-May-2002, Peter Young
            Added MIN_ABUND optional input.

    Ver.3, 28-May-2002, Peter Young
            Corrected way in which DEM is handled.

 PROJECT:  CHIANTI

      CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
      Astrophysical Plasmas. It is a collaborative project involving the Naval
      Research Laboratory (USA), the University of Florence (Italy), the
      University of Cambridge and the Rutherford Appleton Laboratory (UK). 

 NAME

    KARZAS_XS()

 EXPLANATION

    Outputs the photoionization cross-section at the wavelengths WVL for 
    ionization of an N,L electron with ionization energy IONIZ_EN, 
    calculated using the Karzas & Latter (ApJS 6, 167, 1961) formulation. 
    The bound-free gaunt factor is derived from the tables of Karzas & 
    Latter.

 INPUTS

    WVL    Wavelengths (in angstroms) for which cross-sections are 
           required (1-D array).

    N      Principal quantum number of the electron being removed in the 
           ionization.

    L      The orbital angular momentum of the electron being removed in the 
           ionization.

    IONIZ_EN  The ionization energy (in cm^-1) of the electron being 
              removed.

 OPTIONAL INPUTS

    PE      Allows the PE array from READ_KLGFB to be directly input to 
            KARZAS_XS thus avoiding the need to read the K&L data 
            repeatedly for many ions. Requires KLGFB to also be input.

    KLGFB   Allows the KLGFB array from READ_KLGFB to be directly input to 
            KARZAS_XS thus avoiding the need to read the K&L data 
            repeatedly for many ions. Requires PE to also be input.

 OUTPUT

    The photoionization cross-section for the ionization of the outer 
    electron in units of mega-barns (Mb = 10^-18 cm^2) at the input 
    wavelengths. E.g., for Fe XIII (ground configuration 
    1s2.2s2.2p6.3s2.3p2) it is the cross-section for the removal of the 
    3p electron.

 CALLS

    READ_KLGFB

 HISTORY

    Ver.1, 24-Jul-2002, Peter Young

 PROJECT:  CHIANTI

       CHIANTI is an atomic database package for the calculation of
       continuum and emission line spectra from astrophysical plasmas. It is a 
       collaborative project involving the Naval Research Laboratory
       (Washington DC, USA), the Arcetri Observatory (Firenze, Italy), and the
       Cambridge University (United Kingdom).

 NAME:
	LANDSCAPE

 PURPOSE:

	:


 CALLING SEQUENCE:

       LANDSCAPE


 INPUTS:

	None	

	
 KEYWORD PARAMETERS:

	None

 OUTPUTS:

	None



 COMMON BLOCKS:

	None


 EXAMPLE:

    to make a postscript file in landscape orientation

             > set_plot,'ps'
             > landscape
             > plot,x,y
             > device,/close
             > set_plot,'x'

 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	March 1996:     Version 2.0

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	LATEX_WVL_DEM

 PURPOSE:

	create a latex file of predicted spectral line intensities and
       wavelengths corresponding to a selected abundance and differential
       emission measure (DEM)


 PROCEDURE:

                 Calculations are done assuming either constant density or
                 constant pressure. See CH_SYNTHETIC for details.


 CALLING SEQUENCE:

       LATEX_WVL_DEM, Wmin, Wmax, Pressure= , [density= ], $ 
              [outfile= , mini= , sngl_ion=, /photons, /all, /masterlist]


 INPUTS:

	Wmin:   lower limit of the wavelength/energy range of interest (Angstroms)
               if kev keyword set, then wmin is in kev	

	Wmax:   upper limit of the wavelength/energy range of interest (Angstroms)
               if kev keyword set, then wmax is in kev	

       Pressure:  pressure in emitting region (cm^-3 K), or 
       Density:   density in emitting region (cm^-3).


 OPTIONAL INPUTS:


       OUTFILE: the name of the output latex file to be written.
	
	MINI:	Minimum intensity for a line to be included in the output.

	SNGL_ION:  specifies  a single ion (e.g. SNGL_ION='Fe_10' to include
                 only Fe X lines) or an array (e.g. SNGL_ION=['Fe_10','Fe_11']
                 to include only Fe X and Fe XI lines) of ions to be used
                 instead of the complete set of ions specified in
                 !xuvtop/masterlist/masterlist.ions 

       MASTERLIST: string of a specific masterlist file (full path). 
                   If defined as a keyword (i.e. MASTERLIST=1 or /MASTERLIST)
                   then a widget allows the user to select a  user-defined
                   masterlist file. Shortcut for SNGL_ION.   

       RPHOT   Distance from the centre of the star in stellar radius units.
               I.e., RPHOT=1 corresponds to the star's surface. (Default is
               infinity, i.e., no photoexcitation.)

       RADTEMP The blackbody radiation field temperature (default 6000 K).
 

 OUTPUTS:

	a latex file:   'linelist.tex'  in the working directory by default


 OPTIONAL OUTPUTS:

	
 KEYWORD PARAMETERS:

	MINI:	Minimum intensity for a line to be included in the output

	SNGL_ION:  specifies  a single ion (e.g. SNGL_ION='Fe_10' to include
                 only Fe X lines) or an array (e.g. SNGL_ION=['Fe_10','Fe_11']
                 to include only Fe X and Fe XI lines) of ions to be used
                 instead of the complete set of ions specified in
                 !xuvtop/masterlist/masterlist.ions 

       MASTERLIST: string of a specific masterlist file (full path). 
                   If defined as a keyword (i.e. MASTERLIST=1 or /MASTERLIST)
                   then a widget allows the user to select a  user-defined
                   masterlist file. Shortcut for SNGL_ION.   


       PHOTONS:  units will be in photons rather than ergs

       KEV:  wavelengths will be given in kev rather than Angstroms

       ALL:  if set, then all lines are included.  This means that lines for which
             only an approximate wavelength is known (only theoretical energy
             levels are known) are included.


       OUTFILE:  the name of the output latex file to be written. By default a
                file 'linelist.tex' in the user's working  directory will be
                created. 

       NOPROT   If set, then proton rates are not included.


 CALLS:
       
       CH_SYNTHETIC, CH_LINE_LIST


 COMMON BLOCKS: None

 RESTRICTIONS:

 SIDE EFFECTS:


 EXAMPLE:

             > latex_wvl_dem, 400.,800., mini=1, pressure=1.e+15,sngl_ion='o_4'


 CATEGORY:

	spectral synthesis.

 WRITTEN     : 

       Version 1, 8-Nov-01, Giulio Del Zanna (GDZ). 

       Compared to the previous LATEX_WVL_DEM, these are the main changes:

       1-Rewritten as a wrapper routine using the new procedures.
       2-Now the PRESSURE value is a keyword.
       3-The calculations can be done at constant DENSITY.
       4-MASTERLIST can now be used both as an input string or as a keyword.


 MODIFICATION HISTORY:

       Version 2, 18-Nov-01, Peter Young
           Added /noprot, rphot and radtemp keywords.

       V. 3, 22-May-2002 GDZ.  Removed const_net definitions.
             
 VERSION     : Version 3, 22-May-2002

 PROJECT     :  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 

                   
 NAME        : MAKE_CHIANTI_SPEC
     		          
 PURPOSE     : 
              To create a CHIANTI synthetic spectrum 
               
 CALLING SEQUENCE:

       IDL> make_chianti_spec, TRANSITIONS,  LAMBDA, SPECTRUM,$ 
                    [BIN_SIZE= ,  ,INSTR_FWHM= , PIXEL=PIXEL, BINSIZE = BINSIZE, $
                    WRANGE= , ALL=ALL, continuum=continuum, $
                    ABUND_NAME= , MIN_ABUND=, photons=photons, effarea=effarea


 PROCEDURE : 
 		
     From information contained in the structure TRANSITIONS, constructs 
     a synthetic spectrum

     By default, routine assumes thermal widths for lines.

   PROGRAMMING NOTES

     The line profile is constructed using the IDL gaussint routine. 
     For a wavelength pixel centred at l and with width dl, gaussint 
     is used to integrate the Gaussian up to l-dl/2 and up to l+dl/2. 
     The difference between the two is the intensity in this pixel.


    
 INPUTS      : 
		
               TRANSITIONS, the structure created by ch_synthetic.pro.
               
 OPT. INPUTS : 

     LAMBDA   Array of wavelengths (X-values). If not defined as input, it is
              calculated on the basis of BIN_SIZE, and returned as an output. 
              If defined as input, the routine checks that there are at least
              10 points in the wavelength range defined by WRANGE. If there
              are, the corresponding subset of LAMBDA is returned, otherwise
              the routine exits with an error.

     BIN_SIZE      Bin size  in Angstroms of the spectrum to be created. A linear
              spectrum is assumed. In case an effective area file is used, the
              wavelenghts in the file (that might not be linear) are used to
              create the spectrum, and this bin size looses any meaning.

     WRANGE   Allows a subset of the wavelength range to be turned into 
              a spectrum. When using syn_plot, this speeds up the routine 
              a lot if you've elected to zoom in on a region.

     INSTR_FWHM Instrumental FWHM (Angstroms). 
                In case an effective area file is used, The line intensities
                contributing to each bin are summed, and subsequently convolved
                with a gaussian of full-width-half-maximum FWHM if FWHM is not
                set = 0 . Please make sure that the FWHM value (if not set to
                zero) is larger than  the bin size. 

     ABUND_NAME  A CHIANTI abundance file name can be set. 
                It allows the abundance file given in transitions.abund_name
                (if present)   to be over-ridden. Note that it also used for
                the continuum calculation.

     MIN_ABUND: If set, calculates line intensities only from those elements
                  which  have an abundance greater than min_abund. 
                  Can speed up the calculations. For example, from Allen
                  (1973):

                   abundance (H)  = 1.
                   abundance (He) = 0.085
                   abundance (C)  = 3.3e-4
                   abundance (O)  = 6.6e-4
                   abundance (Si) = 3.3e-5
                   abundance (Fe) = 3.9e-5

     FILE_EFFAREA
                   The Effective Area File (TWO COLUMNS - wavelengths in
                   Angstroms and cm^2 values) If defined, then the spectrum is
                   multiplied with these values.  Any input  LAMBDA value is
                   over-written by the wavelenghts in the file (that might not
                   be linear) and  are used to create the spectrum.
		    Note that this option only works well if a sufficient number
		    of bins is given. The line intensities contributing to each
		    bin are summed, and  subsequently convolved with a gaussian
		    of full-width-half-maximum FWHM, if FWHM is not set = 0.
                   Please note that the convolution might not work if a small
                   number of  bins is defined. 

               
 OUTPUTS     : 
		
		LAMBDA  Array of wavelengths (X-values).
              If not defined as input, it is
              calculated on the basis of BIN_SIZE, and returned as an output. 
              If defined as input, the routine checks that there are at least
              10 points in the wavelength range defined by WRANGE. If there
              are, the corresponding subset of LAMBDA is returned, otherwise
              the routine exits with an error.


               SPECTRUM  A structure containing all the information:

                     LAMBDA      The array of X-values
                     SPECTRUM    The array of Y-values
                     UNITS       The units of LAMBDA, SPECTRUM
                     INSTR_FWHM  The Instrumental FWHM
                     BIN_SIZE    Width of the Bins  (fixed) in angstroms
                     ABUND_NAME  The CHIANTI abundance file name             
                     ABUND       The abundance values
                     MIN_ABUND   The minimum abundance value used                 
                     ABUND_REF   The references
                     CONTINUUM   The values of the continuum (if calculated)
                     
                     FILE_EFFAREA The Effective Area File used (optional)
                     EFFAREA       The array of effective area values
                                 (optional - same size of LAMBDA)

                    .LINES      An array of structures, for all the lines used               
                                to calculate the SPECTRUM. 
                                The tags are the same as those created by 
                                CH_SYNTHETIC, plus
                       .PEAK    The peak intensity of the line in the spectrum
                                (approx. value) 
	
 OPT. OUTPUTS:
		
     BINSIZE  If BIN_SIZE  is not  specified, then the spectrum 
              bin-sizes are computed automatically, and the size of the 
              bin returned in BINSIZE.


 KEYWORDS    : 

     PIXEL    The spectrum is given in /pixel units rather /ang
        (DISABLED)
      
     ALL      Add  lines that originally had negative wavelengths  
               
     PHOTONS  If set=1, the output intensities will be in photons instead of 
                  ergs.

     CONTINUUM
              If set, then the  continuum is added to the 
              spectrum.

     verbose 

 CALLS       : 
		
		PRY:     	GET_ATOMIC_WEIGHTS
		Chianti: FREEBOUND, FREEFREE
		
 COMMON       (with freefree freebound and two_photon):
 		
		elements,abund,abund_ref,ioneq,ioneq_logt,ioneq_ref

 RESTRICTIONS: The input structure has to be of the type created by ch_synthetic.
               The LAMBDA, EFFAREA values must be ordered in wavelength and the
               LAMBDA values must be in Angstroms.
               
 SIDE EFFECTS: None known yet.
               

 EXAMPLES    : 
		
		make_chianti_spec, output_struct,  LAMBDA, SPECTRUM,$
		 bin_size=0.01, instr=0.1 

 CATEGORY    : 
               spectral synthesis.

 PREV. HIST. :

      
 WRITTEN     : 
           Peter Young , CfA, pyoung@cfa.harvard.edu  1-Sept-2000

 MODIFICATION HISTORY:  
 
               Version 1, PRY 1-Sept-2000

               Version 2, Giulio Del Zanna (GDZ)  10-Oct-2000

               put ALL keyword, removed the FWHM obsolete and
               confusing call. Reorganised various minor things.

               Version 3, PRY 19-Oct-2000
                 Corrected the way continuum is treated for an isothermal 
                 spectrum.

               V. 4, 2-Nov-2001 GDZ. Now MIN_ABUND is effective not only in the
               continuum calculation but also in the line spectrum.
               Modified for the use of logt_isothermal

               V.5, GDZ, added EFFAREA keyword: an ascii file with lambdas and
                                              effective areas can be read
                                              in. The line intensities are
                                              calculated in a different way.
                        Also, changed the output.

               V.6, GDZ, 28-Apr-02 redefined completely the OUTPUT structure. 
                    Major revision (added two_photon verbose).

               V.7, GDZ, 3-May-2002
                    fixed  a bug, when negative angpix values occur.
                     
               V.8, GDZ, 22 May 2002,  changed some tags of the output, and
                    added min_abund in the continuum call.

               V.9, GDZ, 30-May-02 replaced fix() with round() 

               V. 10, 15-July-2002 , GDZ 
                    changed the location of Effective area files.

               V.11 14-Aug-02, GDZ 
                    speeded up the routine, by changing the way the PEAK tag is
                    added to the structure. The drawback is that only the
                    'standard v.4 tags' are allowed, and future additions will
                    have to be dealt properly.
  
               v.12 2-Dec-2002, GDZ. 
                   Fixed a bug:  Removed the plotting of the window with the effective areas.

               v.13 26-Apr-2005, Enrico Landi (EL)
                   Fixed a minor bug: if the lines were more than 32768 (2^15), the main
                                loop crashed.

               v.14 22-Jul-2005 GDZ 
                 -fixed a bug. When the routine was run once without
                 defining the lambdas, and then with the lambdas
                 defined (the units were switched to photons)
                 -fixed a bug. When the effective areas were used,
                 all lines were used to create the spectrum.
                 -added hard-wired switch to photons when using
                 effective area files.

                 -added the keV option

                 -now can output a spectrum only with the continuum
                 (i.e. even if no emission lines are present). 

               15, 2-Aug-2005, GDZ 
                 Added a check on the input structure. If it was
                 calculated with ch_synthetic and the keyword
                 /no_sum_int, it cannot be used here.

 VERSION     :  15, 2-Aug-2005

 STILL TO DO: 

              -speed up the routine with the use of arrays.
              -add the option to select only a list of ions, also in the
               continuum procedures.
              -Allow the use of user-defined line profiles.
              -Enable PIXEL keyword

 Project     : SOHO - CDS     
                   
 Name        : MAKE_ION_LIST
               
 Purpose     : Reads masters ions list and interprets.
               
 Explanation : Reads the CHIANTI master ion list and returns the list of 
               available elements and ions in suitable arrays.
               
 Use         : IDL> make_ion_list, elements, ions
    
 Inputs      : None
               
 Opt. Inputs : None
               
 Outputs     : elements - string array of all elements available
               ions     - 2-d string array of roman ionization stages
                          available for each element. (N,M) where N is
                          number of elements and M is large enough to 
                          contain all ionization stages (Null if not used)
               
 Opt. Outputs: None
               
 Keywords    : None

 Calls       : None

 Common      : None
               
 Restrictions: None
               
 Side effects: None
               
 Category    : Spectrum
               
 Prev. Hist. : None

 Written     : C D Pike, RAL, 19-Jan-96
               
 Modified    : V.2 Increased array sizes.   CDP, 25-Jun-96
               V.3. Further increase of the array sizes, and  removed the 'd'
               directories from the masterlist, to be compatible with CHIANTI
                removed call to concat_dir    Giulio Del Zanna 16-Oct-2000. 
               V.4 21-May-2002, GDZ: 
                  generalize directory concatenation to work for Unix, Windows
                  and VMS.
 
 Version     : Version 4 21-May-2002

 NAME

    MATRIX_SOLVER()

 PROJECT

    CHIANTI

 EXPLANATION

    Takes the matrices for the various atomic processes employed in
    CHIANTI and returns the level populations.

 INPUTS

    XNE    Electron density (cm^-3). Scalar.

    AA     2-D array of transition probabilities.

    QQ     2-D array of electron excitation rates.

    PPR    2-D array of proton rates

    AAX    2-D array of photoexcitation/stimulated emission rates.

 OPTIONAL INPUT

    FRAC_CUTOFF The fraction of non-zero elements in the C matrix below
                which the sparse matrix solver is used. The default value
                is zero (i.e., don't use sparse matrix solver).

 OPTIONAL OUTPUT

    C      The 2D matrix containing all rate coefficients.

 OUTPUT

    A 1-D array of level populations, scaled so that the sum of the 
    populations is 1.

 HISTORY

    Ver.1, 1-Jul-2005, Peter Young

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 

 Name        : MAX_TEMP
               
 Purpose     : Calculates temperature at max ionisation ratio for an ion

 Explanation : 
               
 Use         : IDL> print,max_temp(ion)
    
 Inputs      :  ion - the specific ion in the form eg 'Fe_XII' or 'Fe XII'
               
 Opt. Inputs :  None
               
 Outputs     :  Function returns log of max temperature
               
 Opt. Outputs:  None
               
 Keywords    :  ALL - if set produces a plot of all temperatures

 Calls       :  Other CHIANTI routines

 Common      :
               
 Restrictions:  None
               
 Side effects:  None
               
 Category    :  Spectral
               
 Prev. Hist. :  None

 Written     :  C D Pike, RAL, 9-Jun-97
               
 Modified    :  V.2 Update element list.  CDP, 18-Jun-99 
                V.3 modified definition of XUVTOP, and allowed selection of
                ionization eq. file. Giulio Del Zanna (DAMTP) 10-Oct-2000

                V.4, Giulio Del Zanna (GDZ)
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

 VERSION     :   4, 21-May-2002, GDZ 

function	mid2bound
	given mid-bin values, make an intelligent determination of
	the bin boundaries and return said boundaries
	(actually, it's not all that intelligent.  uses spline interpolation)

	given input array of N elements, returns array of N+1 elements.

parameters
	m	[INPUT; required] the mid-bin values from which to
		expand out

keywords
	eps	[INPUT] a small number, default is 1e-6
	verbose	[INPUT] controls chatter
	_extra	[JUNK] here only to prevent crashing the program

history
	vinay kashyap (OctMM)

 Project     : SOHO - CDS     
                   
 Name        : PLOT_CHIANTI_NE
               
 Purpose     : Plots a density sensitive ration saved from CHIANTI_NE
               
 Explanation : The routine CHIANTI_NE allows the calculated ratio to be
               saved in an IDL save file.  This routine retrieves and
               plots the ratio.
               
 Use         : IDL> plot_chianti_ne, file, data
    
 Inputs      : file - save file name (an extension of .CH_NE will have
                                      been added, specifying this is optional)
               
 Opt. Inputs : None
               
 Outputs     : None
               
 Opt. Outputs: data - returns the retrieved ratio structure
               
 Keywords    : log. If set, a log-log plot is produced.

 Calls       : print2d_plot 

 Common      : None
               
 Restrictions: None
               
 Side effects: None
               
 Category    : Synthetic spectra
               
 Prev. Hist. : None

 Written     : C D Pike, RAL, 7-Oct-96
               
 Modified    : v.2 Added a few extra things, including possibility to create a
               postscript file. 
               Giulio Del Zanna (DAMTP), 10-Oct-2000

 Version     : Version 2, GDZ 10-Oct-2000 

 Project     : SOHO - CDS     
                   
 Name        : PLOT_CHIANTI_TE
               
 Purpose     : Plots a temperature sensitive ratio saved from CHIANTI_TE
               
 Explanation : The routine CHIANTI_TE allows the calculated ratio to be
               saved in an IDL save file.  This routine retrieves and
               plots the ratio.
               
 Use         : IDL> plot_chianti_te, file, data
    
 Inputs      : file - save file name (an extension of .CH_TE will have
                                      been added, specifying this is optional)
               
 Opt. Inputs : None
               
 Outputs     : None
               
 Opt. Outputs: data - returns the retrieved ratio structure
               
 Keywords    : log. If set, a log-log plot is produced.

 Calls       : None

 Common      : None
               
 Restrictions: None
               
 Side effects: None
               
 Category    : Synthetic spectra
               
 Prev. Hist. : None

 Written     : C D Pike, RAL, 7-Oct-96
               
 Modified    : v.2 Added a few extra things,  including possibility to create a
               postscript file. 
               Giulio Del Zanna (DAMTP), 10-Oct-2000

 Version     : Version 2, GDZ 10-Oct-2000 

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	PLOT_DEM

 PURPOSE:

	To plot differential emission measure (DEM) values

 CATEGORY:

	Widgets.

 CALLING SEQUENCE:

       PLOT_DEM,filename


 INPUTS:

	filename:  the name of the DEM file to be plotted.  The file must b
                  in the standard CHIANTI format for DEM files.  If filename 
                  is a blank string ('') then an interactive window will come 
                  up to allow the user to select a DEM file from the CHIANTI 
                  DEM directory or some other directory.	

	
 KEYWORD PARAMETERS:

	PSFILE:	If set, the a postscript plot will be place in the 
               file 'psfile' specified by the user


 OUTPUTS:

       None, other than a plot




 EXAMPLE:

             > plot_dem,'ademfile.dem'
         or
             > plot_dem,''

 MODIFICATION HISTORY:

 	Written by:	Ken Dere
	June 1998:     Version 1.0
	Version 2, 21-Dec-2000, William Thompson, GSFC
		Modified for better cross-platform graphics capability

       V.   3, 21-May-2002, Giulio Del Zanna (GDZ) 
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

 VERSION     :   3, 21-May-2002 

 Project     : SOHO - CDS     
                   
 Name        : PLOT_DMM_DR_FIG
               
 Purpose     : Plots line intensities in DMM_DR
               
 Explanation : Internal routine used by CHIANTI_NE for plotting individual
               line intensities.
               
 Use         : Called by CHIANTI_NE
    
 Inputs      : Uses common
               
 Opt. Inputs : None
               
 Outputs     : None
               
 Opt. Outputs: None
               
 Keywords    : None

 Calls       : None

 Common      : dmm_lines
               
 Restrictions: None
               
 Side effects: None
               
 Category    : Spectral, plotting
               
 Prev. Hist. : Originally included in density_ratios by K Dere

 Written     : C D Pike, RAL, 15-Jan-96
               
 Modified    : V.3 Fix bug in searching for peak line (IMAX).  CDP, 27-Jan-96
               Changed charsize in plots.  CDP, 17-Jul-97
               V.4 changed yranges in the plots. Removed common calls not
               needed. Giulio Del Zanna 6-Oct-2000 


 Version     : Version 4, 6-Oct-2000

 Project     : SOHO - CDS     
                   
 Name        : PLOT_DMM_TR_FIG
               
 Purpose     : Plots line intensities in DMM_TR
               
 Explanation : Internal routine used by CHIANTI_TE for plotting individual
               line intensities.
               
 Use         : Called by CHIANTI_TE
    
 Inputs      : Uses common
               
 Opt. Inputs : None
               
 Outputs     : None
               
 Opt. Outputs: None
               
 Keywords    : None

 Calls       : None

 Common      : dmm_lines
               
 Restrictions: None
               
 Side effects: None
               
 Category    : Spectral, plotting
               
 Prev. Hist. : Originally included in density_ratios by K Dere

 Written     : C D Pike, RAL, 15-Jan-96
 Modified    : Fix bug in searching for peak line (IMAX).  CDP, 27-Jan-96
               V.1  H E Mason, 03-Oct-96
               V.2 changed yranges in the plots. Removed common calls not
               needed. reinstated the two plots. Changed various things.
               Giulio Del Zanna (DAMTP), 10-Oct-2000

 Version     : Version 2, 

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 
                   
 Name        : PLOT_IONEQ
               
 Purpose     : Plots the ionisation equilibrium values for an element.

 Explanation : 
               
 Use         : IDL> plot_ioneq, element [ ion=ion]
    
 Inputs      : element - the element name
               
 Opt. Inputs : Ion (as keyword)
               
 Outputs     : None
               
 Opt. Outputs: a postscript file.
               
 Keywords    : ION_RANGE - specify range of ions. E.g., ion_range=[5,8] 
                    means V to VIII inclusive.
               IONEQ_NAME:  Name of the ionization equilization name to use.
                    If not passed, then the user is prompted for it.
               NOT_INTERACTIVE Avoid interactive use.

 Calls       :  Other CHIANTI routines

 Common      :
               
 Restrictions:  None
               
 Side effects:  None
               
 Category    :  Spectral
               
 Prev. Hist. :  None

 Written     :  C D Pike, RAL, 9-Jun-97
               
 Modified    :  V.2. Update element list. modified definition of XUVTOP, and
               allowed selection of ionization eq. file and creation of
               postscript file. 
               Giulio Del Zanna  (DAMTP) 10-Oct-2000 

       V.3, Giulio Del Zanna (GDZ)
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

       V 4, 15-July-2002, GDZ 
         Added keywords ioneq_name, not_interactive

       V.5, 9-Feb-2005, Peter Young
            Changed ion= keyword to ion_range=

 VERSION     :    5, 9-Feb-2005

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	PLOT_POPULATIONS

 PURPOSE:
	plot the population of a number of the lowest levels as a function of 
       electron density for a specific temperature

 CATEGORY:

	science.

 CALLING SEQUENCE:

       PLOT_POPULATIONS,Ion,T,Nlevels


 INPUTS:

       Ion:  CHIANTI style name for the ion, i.e., 'c_6' for C VI
       T:  electron temperature (K)


 OPTIONAL INPUT:
       Nlevels:  the number of levels for which populations are plotted
                 starts from level 1 (the ground level)

	
 KEYWORD PARAMETERS:

	OUTFILE:   the (optional) name of the output file where the listing 
                  is produced
	PSFILE:    the (optional) name of the output file where a postscript 
                  plot produced

	RADTEMP	Specify background radiation temperature (default: 6000 K)

	RPHOT   Distance from the centre of the star in stellar radius units.
               I.e., RPHOT=1 corresponds to the star's surface. (Default is
               infinity, i.e., no photoexcitation.)

       NOPROT  If set, then the default setting will be NOT to use 
               proton rates. This can be changed within the routine.

               NOT_INTERACTIVE Avoid interactive use.

 OUTPUTS:


 COMMON BLOCKS:

	common elvlc,l1a,term,conf,ss,ll,jj,ecm,eryd,ecmth,erydth,eref
       common wgfa, wvl,gf,a_value
       common upsilon,t_type,c_ups,splups

 CALLS

       POP_SOLVER, ION2SPECTROSCOPIC, ION2FILENAME, READ_IP,
       CONVERTNAME, READ_ELVLC, READ_WGFA2, READ_SPLUPS

 EXAMPLE:

 to plot populations of the 5 ground configuration levels of Fe XIII
 and store these values in a file 'Fe_XIII.lis' for a temperature of 1.5 MK

             > plot_populations,'fe_13',1.5e+6,5,outfile='Fe_XIII.lis'

 MODIFICATION HISTORY:

 	Written by:	Ken Dere
	March 1996:     Version 2.0
       November 1997:  Ken Dere, added psfile keyword
       September 1999:  Ken Dere, for Version 3, 
       14-Jul-2000     Peter Young, now calls pop_solver
	Version 6, 21-Dec-2000, William Thompson
		Modified for better cross-platform capability.

       V. 7, 21-May-2002, Giulio Del Zanna (GDZ), modified the plotting bit
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

       V 8, 15-July-2002, GDZ 
         Added keyword  not_interactive

       V 9, 4-Oct-2003, GDZ
                  modified the input to POP_SOLVER, now it is dealt with an
                  input structure.

       V 10, 4-May-2005, Enrico Landi (EL)
                  Modified in order to include ionization and recombination
                  data in the input to POP_SOLVER, now it allows choice of .ioneq
                  file needed to include ionization and recombination.

       V 11, 12-Aug-2005, GDZ 
                  The number of levels is now optional. Also, a check that the
                  number of levels must be less than the levels in the file is
                  now enforced.


 VERSION     :   11, 12-Aug-2005

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME: POP_PLOT
       
 PURPOSE:

	To compute n_j A_ji / N_e for a selected transition(s) and plot it
	against N_e. If it is insensitive to N_e, then the line(s) is 
	suitable for emission measure analysis.

 CATEGORY:

       Atomic data analysis

 EXPLANATION:

	The routine calls EMISS_CALC to give values of DE*n_j*A_ji at the 
	temperature TEMP and densities from 10^8 to 10^12. You are then 
	asked to select which transition(s) you are interested in. (If 
	more than one line is selected, the lines are blended.) 
	DE*n_j*A_ji/N_e is then plotted against density.

	If TEMP is not specified, then the temperature at which the 
	ionisation fraction has its maximum is calculated. For the iron 
	ions, the ion balance calcs of Arnaud & Raymond are used, 
	otherwise Arnaud & Rothenflug are used. If TEMP is specified, 
	and the value is less than 20, then it is assumed that the log 
	of the temperature has been specified.

	In emission measure work it is important to isolate lines for 
	which DE*n_j*A_ji/N_e is insensitive to density. If only such lines 
	are used, then the derived emission measure curve is independent 
	of density.

 CALLING SEQUENCE:

       POP_PLOT, IZ, ION, WRANGE=WRANGE, [TEMP=TEMP, /QUICK, DATA=DATA, $
				DENS_RANGE=DENS_RANGE, DILUTE=DILUTE]

 EXAMPLES:

	POP_PLOT, 26, 14, WRANGE=[330,360]

	- 3 lines should appear in the widget. Selecting 334.17 should show 
	a curve that falls off with density. Choosing 353.83 shows a curve 
	that rises with density. By selecting a blend of the two lines, 
	the curve will be insensitive to density, telling us that only a 
	blend of 334.17 and 353.83 is suitable for emission measure work.

	POP_PLOT, 8, 4, WRANGE=[550,560], TEMP=6.0, /QUICK, DENS_RANGE=[6,10]

	- O IV is a member of the boron sequence, and so calculations take a 
	lot longer. Giving the QUICK keyword speeds things up. The 
	temperature is well away from the T_max of the ion

 INPUTS:

	IZ	The atomic number of the ion

	ION	The spectroscopic number of the ion (e.g., 12 = XII)

 OPTIONAL INPUTS:

	DILUTE	Used to set radiative dilution factor. (Default: 0.0)

	TEMP	The temperature at which calculations are required. Usually 
		this will be the Tmax of the ion.

	DENS_RANGE  The default density range is log Ne = 8 to 12. By 
		    inputting two integers, a different range can be chosen.

	WRANGE  Wavelength range from which lines are required. If not 
		given, then the user is allowed to choose from the complete 
		set of lines for the ion.

       ABUND_FILE  The name of a CHIANTI abundance file. This is used for 
               calculating the proton to electron ratio. Default is 
               !abund_file.

       IONEQ_FILE  The name of a CHIANTI ion balance file. This is used for 
               calculating the proton to electron ratio and evaluating 
               the T_max of the ion. Default is !ioneq_file.

       RADTEMP The blackbody radiation field temperature (default 
               6000 K).

       RPHOT   Distance from the centre of the star in stellar radius 
               units. I.e., RPHOT=1 corresponds to the star's surface. 
               (Default is infinity, i.e., no photoexcitation.)

 OPTIONAL OUTPUTS:

	DATA:	An array that contains the data that is plotted: data(*,0) 
		contains
		the densities, while data(*,1) contains the Y-axis values.

 KEYWORDS:

       NOPROT  If set, then the default setting will be NOT to use 
               proton rates. This can be changed within the routine.

	QUICK:	The density range over which the calculations are done is 
		8 to 12 in 0.2 intervals. This keyword forces the 
		calculations to be done at 0.5 intervals.

 CALLS:

	EMISS_CALC, EMISS_SELECT, READ_IONEQ

 HISTORY:

	Ver.1, PRY 28-Jul-97.
	Ver.2, PRY 23-Sep-97 - added DILUTE keyword for photo-excitation
	Ver.3, PRY 30-May-98 - added DENS_RANGE
	Ver.4, PRY 5-Sep-98  - added call to choose_ioneq
	Ver.5, PRY 7-Apr-99  - tidied up, and introduced call to emiss_select
       Ver.6, PRY 7-Dec-01  - modified for v.4 of CHIANTI

       V. 7, 21-May-2002, Giulio Del Zanna (GDZ) 
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

       V.8, 06-Aug-02 GDZ
              added ABUND_FILE to the call to emiss_calc (was missing).
              Changed the use of CHIANTI system variables. 


 VERSION     : 8,  06-Aug-02

 NAME

      POP_PROCESSES

 PROJECT

      CHIANTI

 PURPOSE:

      Outputs to the screen the contributions of the different physical 
      processes to the population of the specified level within the ion. 


      E.g., for Fe XIII, level 4, the output is:

      Population leaving level 4
        rad. decay:     1.51e+01     39.17%
        e de-exc:       3.56e-01      0.92%
        e exc:          2.28e+01     59.12%
        p de-exc:       2.63e-01      0.68%
        p exc:          4.05e-02      0.11%
        stim. emiss:    0.00e+00      0.00%
        photoexc:       0.00e+00      0.00%
                        --------
                 TOTAL  3.85e+01
      
      Population entering level 4
        rad. decay:     3.59e+01     93.19%
        e de-exc:       3.81e-02      0.10%
        e exc:          1.46e+00      3.79%
        p de-exc:       3.18e-03      0.01%
        p exc:          1.12e+00      2.91%
        stim. emiss:    0.00e+00      0.00%
        photoexc:       0.00e+00      0.00%
                        --------
                 TOTAL  3.85e+01

      which shows that the level population is dominated by electron
      excitation and cascading into the level, and by radiative decay
      out of the level.

      Note that the rates for each physical process are multiplied by the 
      population of originating level (this results in the totals for 
      entering and leaving the level to balance).

      For some ions, ionization and recombination are additional processes
      included when working out the level balance. Because of the way these
      processes are included (see the v.5 paper for details), the populations
      entering and leaving some levels *will not balance*.

 INPUTS

      IZ      The atomic number of the ion

      ION     The spectroscopic number of the ion (e.g., 12 = XII)

 OPTIONAL INPUTS

      LEVEL   The ion level for which information is required.

      DENS    Electron density at which rates calculated (units: cm^-3).
              If not specified, a value of 10^10 is assumed.

      TEMP    Temperature at which rates calculated (units: K). If not set,
              then T_max of the ion is used

      PATH    If the ion data-files are not in the CHIANTI directories, 
              then PATH allows you to choose an alternative location.

      RPHOT   Distance from the centre of the star in stellar radius units.
              I.e., RPHOT=1 corresponds to the star's surface. (Default is
              infinity, i.e., no photoexcitation.)

      RADTEMP Specify background radiation temperature (default: 6000 K)

      N_LEVELS Restrict the ion model to this number of levels. E.g., if
               the CHIANTI model contains 40 levels for the ion, then
               setting N_LEVELS=12 reduces the model to 12 levels.

      RADFUNC  The name of a user-defined function that will generate
               a radiation spectrum as a function of temperature. 
               This radiation field will replace the black-body that
               is assumed when using the RADTEMP keyword in the call
               to pop_solver.

 KEYWORDS

      NOPROT  If set, then the default setting will be NOT to use 
              proton rates. This can be changed within the routine.

 CALLS

      R2W, ZION2FILENAME, PROTON_DENS, POP_SOLVER, SETUP_ION

 EXAMPLES

      One can compare the effect of cascading on a level population by using
      the N_LEVELS keyword. Consider the case of Fe XIV:
        IDL> pop_processes,'fe_14',lev=5
        IDL> pop_processes,'fe_14',lev=5,n_levels=12
      With the first call there are two dominant terms to the population
      entering level 5: approximately 47% for radiative decays (cascading)
      and 53% for electron excitation. Setting n_levels=12, one finds that
      the cascading contribution disappears as there are no longer any
      high-lying levels that cascade into level 5. The cascading provides
      a strong contribution to the population of this level.

 HISTORY

      Ver.1, 11-Sep-2002, Peter Young
      Ver.2, 15-Jan-2004, Peter Young
          modified call to pop_solver following recent revision to
          pop_solver; changed input from IZ,ION to IONNAME to match other
          CHIANTI routines
      Ver.3, 26-May-2005, Peter Young
          changed TEMP and DENS keywords
      Ver.4, 10-Jun-2005, Peter Young
          added common block for ionization/recombination data and modified
          INPUT structure.
      Ver.5, 14-Jun-2005, Peter Young
          routine now prints the percentage contribution of each process;
          added N_LEVELS= keyword
      Ver.6, 1-Jul-2005, Peter Young
          added warning for ions with ionization/recombination

 PROJECT:  CHIANTI

       CHIANTI is an atomic database package for the calculation of
       astrophysical emission line spectra.  It is a collaborative project
       involving Ken Dere (Naval Research Laboratory, Washington DC), 
       Brunella Monsignori-Fossi and Enrico Landi (Arcetri Observatory, 
       Florence), and Helen Mason and Peter Young (DAMTP, Cambridge Univ.).


 NAME:  POP_SOLVER
       
 PURPOSE:

	To solve the level balance equations for Chianti ions.

 CATEGORY:

       Scientific analysis
 
 EXPLANATION:

	This routine solves the level balance equations for the CHIANTI ions. 
       Atomic data is pre-loaded into the COMMON blocks, and so POP_SOLVER 
       can only be called indirectly through other routines.

       The matrix equation Ax=b is solved where A contains all the atomic 
       data (electron rate coefficients, radiative decay rates, proton rate 
       coefficients, photoexcitation rates), x are the level populations, 
       and b a vector set to zeros except for the first element which is 1.

       To solve the matrix equation, pop_solver calls out to the CHIANTI
       routine matrix_solver.

       The matrix A is created from the atomic data in the COMMON blocks. 
       In order to optimise POP_SOLVER, A is created where possible through 
       array operations rather than FOR loops.

       With v.5 of CHIANTI the additional atomic processes of ionization
       and recombination can be included when calculating the level
       populations. These processes are not included in the matrix A.
       Instead the level populations x are 'corrected' for ionization and
       recombination afterwards. This correction is performed by the routine
       correct_pops. More details of this method are found in the CHIANTI
       v.5 paper.

 CALLING SEQUENCE:

	POP_SOLVER, T, XNE, POP, N_LEVELS=N_LEVELS

 INPUTS:

	T	Temperatures, e.g., 10.^6

	XNE	Densities, e.g., 10.^8

 OPTIONAL INPUTS:

	N_LEVELS	This allows the number of levels in the model to 
			be reduced. E.g., if the full model contains 100 
			levels, one could set n_levels=50. This can be 
			useful if one is interested in looking at the 
			effects of cascading from higher levels

       SUM_MWL_COEFFS  An array of coefficients of the same length as 
                       the array of temperatures. Electron and proton rate 
                       coefficients will be calculated at each temperature 
                       and then a weighted sum of the coefficients is 
                       performed using SUM_MWL_COEFFS. This allows 
                       non-Maxwellian energy distributions to be 
                       incorporated into the level balance equations.

       RADFUNC         The name of a user-defined function that will generate
                       a radiation spectrum as a function of temperature. 
                       This radiation field will replace the black-body that
                       is assumed when using the RADTEMP keyword in the call
                       to pop_solver.

       FRAC_CUTOFF     The fraction of non-zero elements in the C matrix below
                       which the sparse matrix solver is used. See the routine
                       matrix_solver for more details.

 OUTPUT:

	POP	An array of level populations of size 
		n_T x n_XNE x n_levels

 OPTIONAL OUTPUTS

       DATA_STR If POP_SOLVER is called for just 1 temperature and density, 
                then the individual data arrays for each of the physical 
                processes can be output through DATA_STR. This allows the 
                user to check for the dominant processes affecting the 
                population of a given level. DATA_STR is a structure with 
                the following tags:

                .aa          A-values (2D array)
                .aax         Photoexcitation/stimulated emission (2D array)
                .cc          Electron rate coefficients (2D array)
                .ccp         Proton rate coefficients (2D array)
                .ion_rate    Ionization rate (1D array)
                .rec_rate    Recombination rate (1D array)
                .correction  Correction factor for level pop (1D array)
                .frac_low    Ratio of N+1 ion fraction to N (scalar)
                .frac_high   Ratio of N-1 ion fraction to N (scalar)

                The 2D arrays are such that, e.g., aa[0,20] 
                corresponds to an excitation, while aa[20,0] is a 
                de-excitation.

                The 1D arrays are simply the rate coefficients into the
                individual levels.

 PROGRAMMING NOTES:

       PROTON RATES
       ------------
       To include the proton rates, it is necessary to have the 
       proton-to-electron ratio. This needs to be calculated before the 
       call to pop_solver, and the resulting ratio(s) passed through 
       'pe_ratio' in the common block 'proton'.

       Note that there is no keyword to switch off proton rates (i.e., 
       no /NOPROT keyword). To switch off proton rates, it is necessary 
       to set pstr=-1. This should be done by the calling routine.


 COMMON BLOCKS:

	None.

 CALLS:

	DESCALE_ALL, PROTON_DENS(), MATRIX_SOLVER(), CORRECT_POPS()

 HISTORY:

	Ver 1, PRY 29-Mar-99
	Ver 2, PRY 30-Apr-99, added call to get_prot_rates
	Ver 3, PRY 15-Dec-99, added deu to upsilon common block in order 
		to be consistent with the main Chianti routines.
	Ver 4, PRY 9-May-00, corrected problem with threshold when dealing 
		with sparse matrices. Basically values less than 1.e-30 in 
		the c-matrix were being set to zero and giving rise to 
		NaN's in certain circumstances.
       Ver.5, PRY 14-Jul-00, changed elvl common block to the elvlc common 
               block which is now the Chianti standard. Also, when 
               descaling upsilons, the routine now uses the Delta-E from 
               the .splups file.
       Ver.6, PRY 9-Aug-00, changed routine to deal better with the 
               dielectronic recombination files
       Ver.7, PRY 17-Aug-00, routine does not call LINBCG now if radtemp 
               is non-zero.
       Ver.8, PRY 29-Aug-00, the sparse matrix section has been disabled.
       Ver.9, PRY 12-Nov-01, calls routine proton_dens() to calculate the 
               proton to electron ratio.
       Ver.10, PRY, 6-Dec-01, corrected bug when there are more levels 
               in .splups file than in .elvlc file (ZnXXV).
       Ver.11, PRY, 11-Jul-02, removed ION keyword
       Ver.12, PRY, 9-Aug-02, within the equation solving section, I've set 
               the population of the ground level (rather the n_level level) 
               to 1, and this seems to stop negative populations appearing 
               in extreme conditions.
       Ver.12, PRY, 21-Aug-02, changed exp(-1/1/a) to exp(-a) in electron
               excitation section which caused a hang-up in some 
               circumstances. Also, the routine now uses vector ECMC 
               (combined experimental and theoretical energies) in 
               determining if a level lies above or below another level. 
               Previously only used the observed energy vector. Also, the 
               exponential in the electron excitation section now uses the 
               (accurate) .elvlc energy separation rather than the .splups 
               energy separation, which can cause significant (~20-30%) 
               differences in level populations of high-lying levels at 
               low temperatures.
       Ver.13, PRY, 10-Sep-02, corrected bug for proton rates. The excitation 
               and de-excitation rates were being swapped.

       V. 14  4-Oct-2003  Giulio Del Zanna (GDZ).
               -removed all COMMON blocks (note that only proton_dens.pro has
                one: COMMON elements,abund,abund_ref,ioneq,ioneq_logt,ioneq_ref)
               -only the essential information input is passed to the routine
                via a new input structure.
               -fixed a bug, that affected all the satellite lines, and was 
                introduced in v.12,  included in  CHIANTI v.4.0.
                basically the ionization potential was not subtracted when
                calculating the Delta E in the exponential.

       V. 15  7-Oct-2004  Enrico Landi (EL)
               Included ionization and recombination as level population 
               processes.

       V. 16  6-Apr-2005  Enrico Landi (EL)
               Included extrapolation of ionization and recombination rates
               for temperatures beyond those provided in the .ci and .rec
               files.

       V. 17  10-Jun-2005  Peter Young
               Tidied up code, introduced call to correct_pops for
               ionization/recombination, and added radfunc= and
               sum_mwl_coeffs= keywords

       V. 18  12-Jul-2005, Peter Young
               Improved implementation of RADFUNC keyword

       V. 19  27-Jul-2005, Peter Young
               Corrected bug when the ionrec structure does not exist.

       V. 20  16-Aug-2005, Peter Young
               Routine now catches any NaN values in the level populations
               and prints a warning. All pops are set to zero in this case.

 VERSION     : 20, 16-Aug-2005 

 Project     : SOHO - CDS     
                   
 Name        : print2d_plot
     		          
 Purpose     : this routine optionally changes the ranges of a 1D plot
               and print the plot to a landscape postscript file.
               
 Explanation : 
 		
		This routine changes the keywords pr, x_min,x_max,y_min,y_max
		in order to change the range of a 2-D plot, or to open a
		SET_PLOT,'ps'   and create a postscript.
               This is done basically repeating the sequence of commands in the
               calling routine, within a loop.


               The routine that calls print2d_plot should have :
      
               window,/free    
                                      ;;to open a window

               x_min=min(lambda) & x_max=max(lambda)   
               y_min=min(sp) & y_max=max(sp)   
               
                                     ;; to set the initial limits of 
                                     ;; a one-dimensional plot. 
               pr=''
               begin_plot_sp:


               plot,lambda,sp,xr=[x_min,x_max],yr=[y_min,y_max],$
                          xstyle=1,ystyle=1 

                                     ;; to plot (etc....)
                
               print2d_plot, pr=pr, x_min=x_min,x_max=x_max,$
                             y_min=y_min,y_max=y_max,$
	                      go_to_line=go_to_line,$
                             out_name=out_name,/ask_name  

               or:
                 print2d_plot, pr=pr, x_min=x_min,x_max=x_max,$
                             y_min=y_min,y_max=y_max,$
	                      go_to_line=go_to_line,$
                             out_name='spectrum.ps' 

                                    ;;to create the ps file spectrum.ps 

               if go_to_line eq 'y' then goto,begin_plot_sp

                

               If you have an image or a stack of images, the limits cannot be
               changed and you should omit the min,max limits.


 Use         : IDL>


 Examples    : 
		
		
		

    
 Inputs      : 
		
               
               
 Opt. Inputs : 


               
 Outputs     : 
		
		
		
	
 Opt. Outputs:
		
	
		

 Keywords    : 



 Calls       : 
		
		
		
		
		
 Common      : None.
 		
		

 Restrictions: None.

               
 Side effects: None known yet.
               
 Category    : 
               
 Prev. Hist. :


      
 Written     : 

       Giulio Del Zanna (GDZ), 
	UCLAN  (University of Central Lancashire, UK) 

 Modified    : Version 1, GDZ Fri Jan 30 12:21:59 1998
                v.2 GDZ added  set_plot, 'ps',/copy ,/inter 02-Feb-2000
		Version 3, 21-Dec-2000, William Thompson
			Modified for better cross-platform capability.

               Ver 4, 1-May-02, GDZ
               Modified the setup to go back to display.


 Version     : Version 4, 1-May-02

 NAME

    PROTON_DENS()

 EXPLANATION

    Calculates the ratio of the proton density to electron density using 
    abundance and ion balance files.

 INPUTS

    TEMP    The logarithm (base 10) of the temperature(s) for which the 
            ratio is required. Can be an array.

 OUTPUT

    An array of same size as TEMP containing the proton-to-electron ratio.

 KEYWORDS

    HYDROGEN If set then the routine computes the ratio of hydrogen to 
             free electrons.

 CALLS

    READ_IONEQ, READ_ABUND

 COMMON BLOCKS

    ELEMENTS

 PROGRAMMING NOTES

    To work out the proton/electron ratio, an ion balance and abundance 
    file are required. These can be specified through the common block, 
    otherwise the default files are assumed (!ioneq_file and !abund_file).

    Because the ion balance data is tabulated only for logT from 4.0 to 
    8.0, the proton/electron ratio can only be calculated for this range. 
    Above and below these temperatures, the values at 8.0 and 4.0 are 
    assumed, respectively.


    I've added a check to see if the temperatures are tabulated at 0.1 
    dex intervals (e.g., 4.0, 4.1, etc.). If they are, then a quicker 
    algorithm is used to calculate p/e ratios. This is useful for 
    synthetic.pro.

 HISTORY

    Ver.1, 5-Dec-2001, Peter Young

    Ver.2, 3-Dec-2001, Peter Young
        Added /hydrogen keyword.

    V. 3, 22-May-2002, GDZ: 
                  generalize directory concatenation to work for Unix, Windows
                  and VMS.

       V.4, 06-Aug-02 GDZ
              Changed the use of CHIANTI system variables. 
   
 VERSION     : 4, 06-Aug-02

 NAME

     R2W()

 EXPLANATION

     Converts a distance above a star into a dilution factor.

 INPUTS

     R     Distance above a star's surface, measured from the star's 
           center, in stellar radii units. E.g., R=1 is the surface.

 OUTPUT

     Radiation dilution factor - a number between 0 and 0.5

 HISTORY

     Ver.1, 8-Aug-2001, Peter Young
     Ver.2, 12-Nov-2001, Peter Young
              catches error if r < 1.

 CONTACT

     Peter Young, CfA, pyoung@cfa.harvard.edu

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 

 NAME:
	RAD_LOSS

 PURPOSE:

       Calculates energy loss rate by free-free (ff), radiative 
       recombination (fb) and by line (bound-bound) radiation.

 CATEGORY:
	
	synthetic spectra

 CALLING SEQUENCE:

       RAD_LOSS,Temperature,Loss_rate


 INPUTS:

	None:  The user will select an elemental abundance file and a 
              ionization equilibrium file through widgets.

  KEYWORDS:

       Pressure:  pressure in emitting region (cm^-3 K)
                  density=pressure/temperature(K)

       Density:   density (cm^-3), constant for all temperatures
                  if neither density or pressure is set, then a default 
                  constant density of 10^10 cm^-3 is used.

       Psfile:    to create a postscript plot of the radiative loss in 
                  the file specified by the name assigned to 'Psfile'

       Outfile:   name of an ascii file where the radiative loss rate 
                  as a function of temperature is output
                   
	RADTEMP	Specify background radiation temperature (default: 6000 K)

	RPHOT   Distance from the centre of the star in stellar radius units.
               I.e., RPHOT=1 corresponds to the star's surface. (Default is
               infinity, i.e., no photoexcitation.)

       NOPROT  If set, then the default setting will be NOT to use 
               proton rates. This can be changed within the routine.



 OUTPUTS:

       Temperature:  array of temperatures (K)
       Loss_rate:    energy loss rate in erg cm^3 s^-1


 PROCEDURE:


  if keyword pressure is set then calculations performed at constant pressure
  if keyword density is set then calculations performed at constant density
  otherwise, density is set to 1.e+10
  
  pressure = density * temperature  (cm^-3 K)

	the user will be asked to select an abundance file and a 
       ionization balance file.

 EXAMPLE:

       > rad_loss,t,r


 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	January 1999:  version 1, adopted from synthetic.pro
	Version 2, 21-Dec-2000, William Thompson
		Modified for better cross-platform capability.

       Ver.3, 6-Dec-2001, Peter Young
               Added /noprot, radtemp and dilute keywords.
               Removed elvlc, wgfa and upsilon common blocks.
               Removed calls to read_ip and read_masterlist (not needed).

       Ver.4, 8-Jul-2003, Peter Young
               Updated routine header (no changes to code).

       V 5, 25-May-2005, GDZ 
                  corrected routine header.

 VERSION     :   5, 25-May-2005, GDZ 

 NAME

       RATE_COEFF()

 PROJECT

       CHIANTI

 EXPLANATION

       Returns the electron rate coefficient in units of cm^3 s^-1.
       Either the entire excitation/de-excitation array for the specified
       ion or, if the TRANS= keyword is used, the excitation rate for
       the specified transition.

 INPUTS

	IONNAME	The CHIANTI ion identifier, e.g., 'o_6' for O VI.

	TEMP	Specify temperature(s) at which upsilon(s) are required. 
		Note that this can be an array. Units: K.

 KEYWORDS

       QUIET   Prevents printing of information to the screen.

 OPTIONAL INPUTS

       TRANS   Level indices for transition, e.g., [1,2] for transition 
               1-2.

       PATH    If the data files are in a different directory from the
               standard CHIANTI distribution, then this keyword should be
               set to the directory. E.g., PATH='/home/mydata/o/o_6'

 OUTPUTS

       Returns the 2D array containing excitation and de-excitation
       coefficients. If E(i) < E(j) then CC(i,j) will be the excitation
       coefficient and CC(j,i) will be the de-excitation coefficent.

       If the keyword TRANS= is set, then the routine only returns the
       excitation coefficient for the specified transition.

 EXAMPLES

       IDL> help,rate_coeff('o_6',3e5)
           DOUBLE    = Array[40, 40]

       IDL> result=rate_coeff('o_6',3e5,trans=[1,3])
        Wavelength:            1031.91
        Exc. rate coeff:    1.913e-008
        De-exc. rate coeff: 1.522e-008
       IDL> print,result
         1.9130775e-008

 CALLS

       CONVERTNAME, ZION2FILENAME, ZION2NAME, SETUP_ION, POP_SOLVER,
       READ_IONEQ, READ_ABUND, PROTON_DENS

 HISTORY

       Ver.1, 22-Jun-2004, Peter Young
       Ver.2, 5-Jul-2005, Peter Young
           updated for v.5 of CHIANTI

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME: RATIO_PLOTTER
       
 PURPOSE:
	A widget-based routine to allow the analysis of density or 
       temperature sensitive ratios.

 EXPLANATION:

	RATIO_PLOTTER is designed to study temperature and density 
       sensitive line ratios. For temperature ratios, just use the 
       keyword /temp; for density ratios just use /dens.

       The routine allows line ratios relative to a 
	particular line (called the 'denominator line') to be viewed. One 
	can either choose a particular numerator, or one can simply view 
	all ratios within a specified wavelength range (see the button widget 
	just above the main plot window).

	In the former case, the numerator line can be chosen either from the 
	strongest lines, or from all lines within a specified wavelength 
       range.

	A wavelength range is selected via the sliders at the lower left of 
	the main widget.

       A default set of emissivity parameters is used initially to create 
       the first plot that you see. To change the parameters, click on the 
       'CHANGE PARAMETERS' button near the top of the GUI. This activates 
       a new set of widgets allowing the user to change whether energy or 
       photon units are needed, whether proton rates are included, the 
       temperature/density range, etc. Note that while the parameters are 
       being changed, the user can not modify the line selection or plot 
       parameters.

	When a particular numerator line has been selected, observed 
	intensities (and error bars) for both the denominator and numerator 
	can be input, and the derived density (plus error bars) can be seen 
	on the plot (click on 'PLOT ERROR BARS'), or in a text widget (see 
       the 'SHOW DERIVED DENSITIES' button).

	The accuracy of the derived density or temperature is limited by the 
	intervals in the emissivity calculation. The intervals can be 
       changed on the widget (there are 4 choices given) and if a new 
       interval is selected, new emissivities should be calculated. 
       Using the smallest intervals will give the highest accuracy for 
       the computed density or temperature.


 CALLING SEQUENCE:

       RATIO_PLOTTER, IZ, ION [, /TEMP, /DENS, EM, PATH=, /NOPROT, $
                      IONEQ_FILE=, ABUND_FILE= ]

 EXAMPLES:

	RATIO_PLOTTER, 26, 13, /TEMP        ; Fe XIII

	RATIO_PLOTTER, 10, 6, /DENS	    ; Ne VI

	RATIO_PLOTTER, 26, 13, /DENS, PATH='/home/new_chianti_data'

 INPUTS:

	IZ:	The atomic number of the ion
	ION:	The spectroscopic number of the ion (e.g., 12 = XII)

 OPT. INPUTS:

	EM:	Save the displayed emissivities to structure EM. This 
		structure is simply the structure EMISS_SELECT used in 
		the routine, with some extra tags. This structure has the 
               tags:

               .lines.emiss  Emissivities of line at requested densities
               .lines.wavel  Wavelength(s) of line (blend)
               .dens         Log10 electron density/densities
               .temp         Log10 electron temperature(s)
               .rphot        Photoexcitation radius
               .radt         Radiation temperature
               .proton       String indicating whether proton rates are 
                             included.
               .date         The date and time at which structure was 
                             created.
               .version      The version of CHIANTI that created the 
                             structure.

	PATH:	Data in the CHIANTI format that is not in the CHIANTI 
		database can be read by specifying the directory in which 
		it lies through PATH.

       ABUND_FILE  The name of a CHIANTI abundance file. This is used for 
               calculating the proton to electron ratio. Default is 
               !abund_file.

       IONEQ_FILE  The name of a CHIANTI ion balance file. This is used for 
               calculating the proton to electron ratio and evaluating 
               the T_max of the ion. Default is !ioneq_file.

 KEYWORDS:

       DENSITY If set then ratios are plotted as a function of 
               density rather than temperature.

       TEMPERATURE  If set then the ratios are plotted as a function of 
               temperature rather than density.

       NOPROT  If set, then the default setting will be NOT to use 
               proton rates. This can be changed within the routine.

 PROGRAMMING NOTES:

	RATIO_PLOTTER is actually a collection of several routines....

	DENS_FINDER	- converts observed ratios into densities
	INDEX_EXTRACTOR	- a device for extracting indices out of arrays
       WAVEL_PLOT      - plots the little window in bottom left of GUI
	DENS_PLOT	- updates the plot window
	DENS_MAIN_EVENT	- responds to widget actions
	SAMPLE_WID 	- sets up the widgets
	RATIO_PLOTTER	- loads up various initial parameters

	The emissivities of all the ion's lines are stored in the 
	structure "emiss", while those of the selected lines are stored 
	in "emiss_sel". This latter can be output into IDL by giving the 
	"EM" optional input on the command line.

	The routine is set up to allow more than one numerator to be 
	displayed at once, but I've never actually found a need to 
	implement this yet. (Note that you'll see "Numerator 1" on 
	the widget.)

 CALLS:

	EMISS_CALC, READ_IONEQ, EMISS_SELECT, ZION2NAME,
	ZION2FILENAME, ZION2SPECTROSCOPIC, PS, PSCLOSE, IS_NUMBER,
       CHIANTI_FONT, TRIM

 INTERNAL PROCEDURES AND FUNCTIONS

       DENS_FINDER, INDEX_EXTRACTOR, DENS_PLOT, DENS_MAIN_EVENT,
       SAMPLE_WID, WAVEL_PLOT

 COMMON BLOCKS

       EMISS_DATA, SELECT, SLIDERS, PLOTTING, RAD_DATA, PROTON_RATES,
       EXTRA, ELVLC, FILES, TEMP

 HISTORY:

	Ver.1: PRY, 15-SEP-97.
	Ver.2: PRY, 6-JUL-98,  added EM and PATH
	Ver.3: PRY, 5-SEP-98,  added call to choose_ioneq
	Ver.4: PRY, 11-JAN-99, added PROTON keyword and widget to allow 
			the addition of proton rates
	Ver.5: PRY, 3-FEB-99,  added a title to the widget, and the name 
			of the ion to the ratio plot title
	Ver.6: PRY, 25-MAR-99, corrected bug for wavelengths > 1000 
			angstroms
	Ver.7: PRY, 1-JUN-99,  routine now works in CDS environment 
			without use_dere_chianti
	Ver.8: PRY, 22-FEB-00, corrected colour problem
       Ver.9: PRY, 17-AUG-00, added windows identifying the numerator 
                       and denominator transitions. This required an 
                       extra routine (MAKE_STRINGS) and a common block 
                       (ELVLC).
       Ver.10: PRY, 25-AUG-00, added buttons to allow a choice between 
                       ratios in energy or photon units.
       Ver.11: PRY, 25-AUG-00, can now specify a wavelength range by 
                       directly typing in the numbers
       Ver.12: PRY, 30-Nov-00, changed call to emiss_select
       Ver.13: PRY, 21-Dec-00, removed set_plot,'x' following help from 
                       Bill Thompson
       Ver.14, PRY, 27-Dec-00, changed switch to tst1 for IDL v5.4
       Ver.15, PRY,  7-Dec-01, changed /prot keyword to /noprot to be 
                       compatible with other CHIANTI routines.
                       Added /temperature keyword.
       Ver.16, PRY, 28-May-02, removed SPLINE calls, changing them to 
                       SPL_INIT and SPL_INTERP; changed density labels to 
                       temperature labels where appropriate.
       Ver.17, PRY, 29-May-02, made treatment of photoexcitation consistent 
                       with other CHIANTI routines.

       V.  18, 29-May-2002, Giulio Del Zanna (GDZ)
                        generalized directory concatenation to work for  Unix,
                        Windows  and VMS.  
                        Now we only call zion2filename.
                        When creating the ps file, ps and psclose are used.

       v.19, 12-Jun-02 GDZ 
             fixed a small bug when finding the names of the files when the
             keyword PATH is given.

       v.20, 2-Aug-02, Peter Young
             made some cosmetic changes following Giulio's suggestions.

       v.21, 5-Aug-02, Peter Young
             made various changes:
               - the emissivity parameters (at top of widget) can only be 
                 changed independently of line selection now
               - the text widgets now check to make sure the user inputs 
                 are numbers.
               - extended the number of tags on the output EM structure

       v.22, 6-Aug-02, Peter Young
             corrected plot problem when viewing all temperature ratios 
             in a fixed wavelength range.

       v.23, 8-Aug-02, Peter Young
             a number of cosmetic changes to make the GUI more 
             user-friendly

       v.24, 13-Aug-02, Peter Young
             changed the temperature/density text widget so that numbers 
             are registered even if the return key has not been hit.

       v.25, 14-Aug-02, Peter Young
             photoexcitation button now works again; also some cosmetic 
             changes
       V.26, 17-Sept-02, GDZ 
             added scrolling in main frame

       V.27, 10-Feb-03, Peter Young
             corrected bug related to fonts on Windows PCs

       V.28, 13-Feb-03, Peter Young
             corrected problem when ion balance data dosen't exist for 
             an ion

       V.29, 18-Feb-03, Peter Young
             added call to routine chianti_font to deal with fonts.

       V.30, 28-Aug-03, Peter Young
             corrected bug when two lines have the same wavelength by
             introducing .ind tag to emiss_sel

       V.31, 3-Nov-03, Giulio Del Zanna 
             Added printout of Ne(Te) vs. ratio values
             Modified format e8.2 to e9.2 for Windows compatibility.

       V.32, 6-Nov-03, Peter Young
             Corrected bug when new emissivities are calculated that
             prevented the emissivites in emiss_sel from being updated.
             Also, the Ne(Te), ratio values are now printed to a pop-up
             window through the new 'SHOW RATIO VALUES' button rather
             than printed to the text window (see V.31).

       V.33, 7-Nov-03, Giulio Del Zanna (GDZ)
             Modified the popup widget by calling xpopup and adding 
             labels. Now it is possible to paste and copy the RATIO 
             values into a file.

       V.34, 12-Dec-03, Peter Young
             Lowered the position of the postscript plot on the paper so
             that the title isn't chopped off on US letter-size paper.

       V.35, 2-Aug-2005, GDZ

             Various modifications. Now the routine handles the
             dielectronic case. Added printing of line lists in the
             line ratio plots. Added the option to print directly to
             the PRINTER. Added the option to SAVE a structure
             containing the emissivities into an IDL save file (using
             SAVEGEN). Added retain=2 to the window. Added
             logarithmic or linear plot switch. Added cleaning of the
             variables at the start of the routine. Various minor
             cosmetic changes.

       V.36, 12-Aug-2005, GDZ
             Reinstated some previous cosmetic features. Also adjusted
             some sizes, added some checks (e.g. minimum is set to 1e-10 if
             plot is in log scale -to avoid log(0)-; automatic scaling cannot
             be set if log scale is on).

       V.37, 15-Aug-2005, Peter Young
             Corrected bug with derived densities when the theoretical ratio
             is double-valued.

       V.38, 15-Aug-2005, Peter Young
             Corrected bug introduced by modification above.

       V.39, 17-Aug-2005, Peter Young
             Adjusted layout of widget, modified printing of wavelengths
             in the plot window, and adjusted plot limits for log scale.

 VERSION     :   39, 17-Aug-2005

 This procedure has a dual purpose: (i) to extract `emiss' indices from
 `emiss_sel' and, (ii) create labels that will be displayed on the plot
 window.
 The lines that comprise the blend are contained in emiss_sel.label 
 as, e.g., '203.79+203.80'. This routine separates this string into 
 the separate wavelengths and looks in emiss.lambda to see which 
 indices they correspond to. The set of indices are output through INDEX.

 INPUT

   I    Index of component in emiss_sel. E.g., for the denominator I=0,
        for the numerator I=1.

 OPTIONAL OUTPUT

   INDEX Integer array of same length as the number of lines in the
         numerator or denominator (based on value of I). The elements
         give the indices of the lines as they appear in the EMISS
         structure.

   PLOT_LABEL A string containing the index to be used when labelling
              the line ratio plots.

 KEYWORD

   PS    Setting this adds an angstrom to the wavelength labels. (Only
         works for the postscript device.)

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	READ_ABUND

 PURPOSE:

	to read CHIANTI abundance files

 CATEGORY:

	science.

 CALLING SEQUENCE:

       READ_ABUND,File,Abundance,Reference


 INPUTS:

	File:  the name (string) of the file containing the abundance values
                (relative to hydrogen) usually of the form 
                 '!xuvtop/abundance/*.abund'


	

 OUTPUTS:

	Abundance:  an array of abuncance values
       Reference:  a string containing the reference to the chosen set
                   of abundances in the scientific literature



 PROCEDURE:

	You can describe the foobar superfloatation method being used here.

 EXAMPLE:

             > read_abund,'allen.abund',abundance,ref
               abundance(26) = abundance of iron relative to hydrogen
               quoted by C.W. Allen in Astrophysical Quantities

 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	March 1996:     Version 2.0

       V.   3, 21-May-2002, Giulio Del Zanna (GDZ) 
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

 VERSION     :   3, 21-May-2002 

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	READ_DEM

 PURPOSE:

	to read values the differential emission measure as a function 
       of temperature

 CATEGORY:

	science.

 CALLING SEQUENCE:

       READ_DEM, File, T, Dem, Ref


 INPUTS:

	File:  the name of the file containing the DEM values, usually in
               !xuvtop/dem/*.dem	


 OUTPUTS:

	T:  Log10 values of temperature (K)
       Dem:  Log10 values of the differential emission measure
       Ref:  the reference to the DEM values in the scientific literature


 OPTIONAL OUTPUTS:

	Describe optional outputs here.  If the routine doesn't have any, 
	just delete this section.



 EXAMPLE:

             > read_dem,!xuvtop+'/dem/active_region.dem',t,dem,ref

 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	March 1996:     Version 2.0

       V.   3, 21-May-2002, Giulio Del Zanna (GDZ) 
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

       Ver.4, 20-Nov-2002, Peter Young
           DEM values of -1 caused errors, so this has been corrected.

 VERSION     :   4, 20-Nov-2002 

 PROJECT:  CHIANTI

       CHIANTI is an atomic database package for the calculation of
       astrophysical emission line spectra.  It is a collaborative project
       involving Ken Dere (Naval Research Laboratory, Washington DC), 
       Brunella Monsignori-Fossi and Enrico Landi (Arcetri Observatory, 
       Florence), and Helen Mason and Peter Young (DAMTP, Cambridge Univ.).


 NAME:
	READ_ELVLC

 PURPOSE:

	to read files containing observed and theoretical energy levels

 CATEGORY:

	science.

 CALLING SEQUENCE:

       READ_ELVLC, File, L1, Term, Conf, ss, ll, jj, Ecm, Eryd, Ecmth, Erydth, Ref


 INPUTS:

	File:	the name of the file 
               i.e., !xuvtop+'/si/si_12/si_12.elvlc' for Si XII

 OPTIONAL INPUTS:

	None:
	

 OUTPUTS:       L1      - level index
                Term    - configuration index
                Conf    - configuration description
                ss      - 2S+1
                ll      - L
                jj      - J
                Ecm     - observed energy (cm^-1)
                Eryd    - observed energy (Rydbergs)
                Ecmth   - theoretical energy (cm^-1)
                Erydth  - theoretical energy (Rydbergs)
                Ref     - reference
               
   note:  the theoretical energies are usually those used in the scattering
          calculation and are only useful for predicting approximate 
          wavelengths


 EXAMPLE:

             > file = !xuvtop+'/si/si_12/si_12.elvlc'
             > read_elvlc,file,l1,term,conf,ss,ll,jj,ecm,eryd,ref
             > 

 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	March 1996:     Version 2.0

       Ver.2, 6-Dec-2001, Peter Young
          Modified the form of the "term" output. The J-value is now 
          represented by a fraction rather than a decimal.

 PROJECT:  CHIANTI

       CHIANTI is an atomic database package for the calculation of
       continuum and emission line spectra from astrophysical plasmas. It is a 
       collaborative project involving the Naval Research Laboratory
       (Washington DC, USA), the Arcetri Observatory (Firenze, Italy), and the
       Cambridge University (United Kingdom).


 NAME:
	READ_ELVLC_DIRECT

 PURPOSE:

	to read files containing observed energy levels
       does not reformat some variables like READ_ELVL

 CATEGORY:

	science.

 CALLING SEQUENCE:

       READ_ELVLC_DIRECT, File, L1, Term, Conf, ss, ll, spd, jj, Ecm, Eryd, Ecmth, Erydth, Ref


 INPUTS:

	File:	the name of the file 
               i.e., !xuvtop+'/si/si_12/si_12.elvl' for Si XII

 OPTIONAL INPUTS:

	None:
	

 OUTPUTS:       L1    - level index
                Term  - configuration index
                Conf  - configuration description
                ss    - 2S+1
                ll    - L
                spd   - 'S', 'P', etc to denote L value
                jj    - J
                Mult  - multiplicity  2J+1
                Ecm   - energy (cm^-1)
                Eryd  - energy (Rydbergs)
                Ecmth - energy (cm^-1)
                Erydth- energy (Rydbergs)
                Ref   - reference
               




 EXAMPLE:

             > file = !xuvtop+'/si/si_12/si_12.elvl'
             > read_elvlc_direct,file,l1,term,conf,ss,ll,jj,ecm,eryd,ecmth,erydth,ref
             > 

 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	March 1996:     Version 2.0

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	READ_FBLVL

 PURPOSE:

	To read files containing observed free-bound energy levels

 CATEGORY:

	Science.

 CALLING SEQUENCE:

       READ_FBLVL, File, L1, Conf, pqn, ll, spd, mult, Ecm, Ecmth, Ref


 INPUTS:

	File:	the name of the file 
               e.g., !xuvtop+'/si/si_12/si_12.fblvl' for Si XII

 OPTIONAL INPUTS:

	None:
	

 OUTPUTS:       L1    - level index
                CONF  - configuration description
                PQN   - principal quantum number of electron being ionized
                LL    - L-value of ionized electron
                SPD   - 'S', 'P', etc to denote L value
                MULT  - multiplicity  2J+1
                ECM   - energy (cm^-1)
                ECMTH - energy (cm^-1)
                REF   - reference
               
 EXAMPLE:

             > file = !xuvtop+'/si/si_12/si_12.elvlc'
             > read_fblvl,file,l1,conf,pqn,ll,mult,ecm,ecmth,ref
             > 

 HISTORY

      Ver.1, 31-Jul-2002, Peter Young

 PROJECT:  CHIANTI

       CHIANTI is an atomic database package for the calculation of
       continuum and emission line spectra from astrophysical plasmas. It is 
       a collaborative project involving the Naval Research Laboratory
       (Washington DC, USA), the Arcetri Observatory (Firenze, Italy), and the
       Cambridge University (United Kingdom).

 NAME:
       READ_GFFGU

 PURPOSE:

       Read gffgu.dat file containing free-free gaunt factors of 
             R. S. Sutherland, 1998, MNRAS, 300, 321
             note:  the file available from the web site are mislabelled


 CALLING SEQUENCE:

       READ_GFFGU,g2,u,gff


 INPUTS:

       None    
       

 OUTPUTS:

       g2,u,gff defined in the paper by Sutherland



 COMMON BLOCKS:

       None



 MODIFICATION HISTORY:
       Written by:     Ken Dere
       April 2000:     Version 3.0
       October 2001:   Version 4 - Ken Dere -
                       corrected for the fact that the original
                       Sutherland file was mislabelled
       November 2001:  Corrected the address of the gffgu.dat file - Enrico Landi

 PROJECT:  CHIANTI

       CHIANTI is an atomic database package for the calculation of
       continuum and emission line spectra from astrophysical plasmas. It is a 
       collaborative project involving the Naval Research Laboratory
       (Washington DC, USA), the Arcetri Observatory (Firenze, Italy), and the
       Cambridge University (United Kingdom).

 NAME:
	READ_GFFINT

 PURPOSE:

	Read gffint file containing integrated free-free gaunt factors of 
             R. S. Sutherland, 1998, MNRAS, 300, 321


 CALLING SEQUENCE:

       READ_GFFINT,g2,gff,s1,s2,s3


 INPUTS:

	None	

	

 OUTPUTS:

	g2,gff,s1,s2,s3 defined in the paper by Sutherland




 COMMON BLOCKS:

	None



 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	April 2000:     Version 3.0

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	READ_IONEQ

 PURPOSE:

	to read files containing the ionization equilibrium values

 CATEGORY:

	science.

 CALLING SEQUENCE:

       READ_IONEQ, File, T, Ioneq, Ref


 INPUTS:

	File:	for example, !xuvtop+'/ioneq/arnaud_rothenflug.ioneq'

 OPTIONAL INPUTS:

	None:
	

 OUTPUTS:

	T:  array of log10 temperatures
       Ioneq:  3-d array (T,element,ion) 
               of the fractional abundance of the ion in
              ionization equilibrium.
       Ref:  reference in the scientific literature


 EXAMPLE:

             > read_ioneq,!xuvtop+'/ioneq/arnaud_rothenflug.ioneq'
             > help,t,ioneq
             > T               FLOAT     = Array(41)
             > IONEQ           FLOAT     = Array(41, 28, 29)
             > print, minmax(t)
             >  4.00000      8.00000
             > print,t(20)
             >  6.0000
             > print,ioneq(20,25,9)
             >   0.269                  = fractional abundance of  Fe X in
                                          ionization equilibrium 

 MODIFICATION HISTORY:
 	Written by:	Ken Dere (KPD)
	March 1996:     Version 2.0
       March 1999:     KPD to read both number of temperature and number 
                       of elements

       25-Oct-2000     V. 4, Giulio Del Zanna (GDZ).
                       Corrected to interpret the '-1' as a reference only
                       if within the first 3 columns

       V.  5, 21-May-2002, Giulio Del Zanna (GDZ) 
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

       v.6, 25-Oct-2004, Peter Young
            modified format statement so that it will read any number of
            temperatures.

       V 7, 25-May-2005, GDZ 
                  corrected routine header.

 VERSION     :   7, 25-May-2005

 PROJECT:  CHIANTI

       CHIANTI is an atomic database package for the calculation of
       continuum and emission line spectra from astrophysical plasmas. It is a 
       collaborative project involving the Naval Research Laboratory
       (Washington DC, USA), the Arcetri Observatory (Firenze, Italy), and the
       Cambridge University (United Kingdom).


 NAME:
	READ_IP

 PURPOSE:

	to read values of ionization potentials 


 CALLING SEQUENCE:

       READ_IP, File, IP, Ref


 INPUTS:

	File:  the name of the file containing the IP values, usually
               !xuvtop/ip/chianti.ip	


 OUTPUTS:

	IP:  Array values of ionization potential (cm^-1)
       Ref:  the reference to the IP values in the scientific literature





 EXAMPLE:

             > read_ip,!xuvtop+'/ip/chianti.ip',ip,ref
                  ip(2-1,2-1) give the ionization potential of He II  (Z=2, Ion=2)

 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	March 1998:     Version 1.0

 PROJECT:  CHIANTI

       CHIANTI is an atomic database package for the calculation of
       continuum and emission line spectra from astrophysical plasmas. It is a 
       collaborative project involving the Naval Research Laboratory
       (Washington DC, USA), the Arcetri Observatory (Firenze, Italy), and the
       Cambridge University (United Kingdom).


 NAME:
	READ_KLGFB

 PURPOSE:

	to read CHIANTI files file containing the free-bound gaunt factors for n=1-6
       from Karzas and Latter, 1961, ApJSS, 6, 167

 CATEGORY:

	science.

 CALLING SEQUENCE:

       READ_KLGFB,PE,GFB


 INPUTS:

	File:  none


	

 OUTPUTS:

	PE:   an array of natural log of 41 values of Photon Energy values relative to 
             the recombination edge i.e., at the recombination edge, PE=0.
       GFB:  an array containing the natural log of free-bound gaunt factors indexed 
             by energy, n and l



  PROCEDURE:  reads the file:  '!xuvtop/continuum/klgfb.dat'

   

 EXAMPLE:

             > read_klgfb,pe,klgfb
                  the free-bound gaunt factor vs. energy for recombination to a hydrogen 2p state
                  (n=2 and l=1) is given by klgfb(*,n-1,l-1)

 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	July 2002:     Version 1.0
             Version 2, 8-Aug-02, GDZ
             corrected a typo.

 VERSION     :   V.2, 8-Aug-02

 PROJECT:  CHIANTI

       CHIANTI is an atomic database package for the calculation of
       continuum and emission line spectra from astrophysical plasmas. It is a 
       collaborative project involving the Naval Research Laboratory
       (Washington DC, USA), the Arcetri Observatory (Firenze, Italy), and the
       Cambridge University (United Kingdom).


 NAME:
	READ_MASTERLIST

 PURPOSE:

	read the masterlist.ions types of file and output a list of ions

 CATEGORY:

	science.

 CALLING SEQUENCE:

       READ_MASTERLIST,filename,list


 INPUTS:

	filename:   name of the masterlist file
	

	
 KEYWORD PARAMETERS:

	none

 OUTPUTS:

	list:  list of ions



 COMMON BLOCKS:

	none;


 EXAMPLE:

             > read_masterlist,'!xuvtop/masterlist.masterlist.ions',list

 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	December 1998:  first version  

 PROJECT:  CHIANTI

       CHIANTI is an atomic database package for the calculation of
       continuum and emission line spectra from astrophysical plasmas. It 
       is a 
       collaborative project involving the Naval Research Laboratory
       (Washington DC, USA), the Arcetri Observatory (Firenze, Italy), and the
       Cambridge University (United Kingdom).


 NAME:
	READ_SPLUPS

 PURPOSE:

	to read file containing spline fits to the Burgess-Tully scaled
       collision strengths

 CATEGORY:

	science.

 CALLING SEQUENCE:

       READ_SPLUPS, File, Splstr, Splref


 INPUTS:

	File:	the name of the input file, i.e. !xuvtop/si/si_4/si_4.splups


 OUTPUTS:

       SPLSTR  Structure containing the data from the file. The tags are 
               as follows:

               .lvl1   lower level index
               .lvl2   upper level index
               .t_type transition type
               .gf     gf value
               .de     Delta-E for transition (rydbergs)
               .c_ups  the scaling parameter
               .nspl   
               .spl    Vector of length 9, containing spline points


 OPTIONAL OUTPUTS

       SPLREF  String array containing references.

 KEYWORDS

       PROT    Allows reading of .psplups files for proton rates.


 PROCEDURE:

	see Burgess and Tully, 1992, Astronomy and Astrophysics, 254, 436.

 EXAMPLE:

       > read_splups, !xuvtop+'/si/si_4/si_4.splups',splstr,splref

 PROGRAMMING NOTES

       This routine is marginally quicker (20-25%) reading the .splups 
       files than Ken's original routine. The improvement in speed is 
       through minimising the lines of code in the WHILE loop.

 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	March 1996:     Version 2.0

       Ver.3, 23-Jan-01, Peter Young
                completely revised. Now reads into a structure and 
                handles 9 point spline fits.

       Ver.4, 26-Jan-01, Peter Young
                speeded up routine

       Ver.5, 22-Mar-01, Peter Young
                now checks if file exists

 PROJECT:  CHIANTI

       CHIANTI is an atomic database package for the calculation of
       continuum and emission line spectra from astrophysical plasmas. It is a 
       collaborative project involving the Naval Research Laboratory
       (Washington DC, USA), the Arcetri Observatory (Firenze, Italy), and the
       Cambridge University (United Kingdom).


 NAME:
	READ_WGFA

 PURPOSE:

	:

 CATEGORY:

	science

 CALLING SEQUENCE:

       READ_WGFA, File, Lvl1, Lvl2, Wvl, Gf, A_value, Ref


 INPUTS:

	File:  name of the file containing the radiative data
                i.e. !xuvtop/c/c_4/c_4.wgfa


 OUTPUTS:

	Lvl1:  1D array of indices of the lower level (starting at 1)
       Lvl2:  1D array of indices of the upper level (starting at 1)
       Wvl:   2D array of transition wavelengths in Angstroms
       Gf:    2D array of weighted oscillator strength gf
       A_value:  2D array of radiative transition probability (s^-1)
       Ref:   1D string array of references to the data in the scientific literature



 EXAMPLE:

             > read_wgfa,!xuvtop+'/c/c_4/c_4.wgfa',lvl1,lvl2,wvl,gf,a,ref
             

 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	March 1996:     Version 2.0

       v.3, 6-Mar-02, Peter Young
           Changed the way the reference string is read in order to 
           prevent '-1' problems.

       v.4, 12-Mar-02, Peter Young
           Corrected bug following above change.

 PROJECT:  CHIANTI

       CHIANTI is an atomic database package for the calculation of
       continuum and emission line spectra from astrophysical plasmas. It is a 
       collaborative project involving the Naval Research Laboratory
       (Washington DC, USA), the Arcetri Observatory (Firenze, Italy), and the
       Cambridge University (United Kingdom).


 NAME:
	READ_WGFA2

 PURPOSE:

	read radiative data files
         a modified version of read_wgfa
         needed to take account of two types of transitions between the same 2 levels:
         for example, the M1 and the 2 photon E1 transition 1s-2s in hydrogenic ions


 CATEGORY:

	science

 CALLING SEQUENCE:

       READ_WGFA2, File, Lvl1, Lvl2, Wvl, Gf, A_value, Ref


 INPUTS:

	File:  name of the file containing the radiative data
                i.e. !xuvtop/c/c_4/c_4.wgfa


 OUTPUTS:

	Lvl1:  1D array of indices of the lower level (starting at 1)
       Lvl2:  1D array of indices of the upper level (starting at 1)
       Wvl:   1D array of transition wavelengths in Angstroms
       Gf:    1D array of weighted oscillator strength gf
       A_value:  1D array of the total radiative transition probability (s^-1)
       Ref:   1D string array of references to the data in the scientific literature



 EXAMPLE:

             > read_wgfa2,!xuvtop+'/c/c_4/c_4.wgfa',lvl1,lvl2,wvl,gf,a,ref
             

 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	March 1996:     Version 2.0

       V.3, 3-Nov-03, Giulio Del Zanna (GDZ)
        Modified size of input arrays. Now the routine can read a file up to
        30 000  lines.

          
 VERSION     :  3,  3-Nov-03

function	rebinw
	rebins the input array on a new grid and returns the output array.
	this routine is preferred over simple INTERPOL or SPLINE because
	this is guaranteed to e.g., conserve energy while rebinning spectra.

syntax
	ff=rebinw(f,x,y,/perbin,nbin=nbin,wrange=wrange)

parameters
	f	[INPUT; required] array values
	x	[INPUT; required] absissae for F
		1: if size matches that of F, assumed to be mid-bin values
		2: if size is size(F)+1, assumed to be bin boundaries
		   (i.e., all the bin-beginners and a final bin-ender)
		3: if neither of the above, this is assumed to be the
		   desired *output* grid, and the absissae of the input
		   are assumed to span the linear range 1..N(F)
		   * Y is ignored on input, but will be overwritten on output
	y	[I/O] the new absissa values
		1: if scalar or 1-element vector on input, assumed to be
		   number of bins in output
		   * linear binning if +ve, log binning if -ve
		2: if >1-element vector on input, assumed to be the desired
		   output grid of bin boundaries, with the last element
		   defining the final bin-ending value.
		3: if not defined, takes value from NBIN
		NOTE: F extrapolates as zeros.

keywords
	perbin	[INPUT] if set, assumes that units of F(X) are [.../bin]
	nbin	[I/O] number of bins in output
		* overwritten if defined via X or Y
		* linear binning if +ve, log binning if -ve
		* default: 1
	wrange	[INPUT] output grid range
		* ignored if defined via array Y (or X -- case 3)
		* overrides if determined via X and CASE 1 of Y
		* default: [1.,500.]
	_extra	[JUNK] here only to prevent crashing the program

restrictions
	beware that if Y is not sorted in ascending order, on output
	it will be!
	requires external procedure FINDEX.PRO

history
	vinay kashyap (Jan98)
	forced x to be required inputs (Jun98)
	changed call to INTERPOL to combo call to INTERPOLATE/FINDEX (VK;99Jul)
	corrected long-standing "feature" of NBIN being useless, changed
	  default behavior of Y=UNDEFINED, NBIN, and X=/=F (VK; MarMM)

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 

 NAME:
	SETUP_ELEMENTS


 PURPOSE:  read in ionization equilibrium and abundances
           not for general user use


 CALLING SEQUENCE:

       SETUP_ELEMENTS


 INPUTS:

	None	

 OUTPUTS:  reads data into common block


 COMMON BLOCKS:

	common elements,abund,abund_ref,ioneq,ioneq_logt,ioneq_ref



 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	Feb.  2000:     Version 1.0 for CHIANTI version 3
       V. 2, 21-May-2002, Giulio Del Zanna (GDZ):
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

       V. 3, 16-Apr-2003, Peter Young
                   I had to use expand_path for DIR in order for the paths to be 
                   recognised in Windows.

 VERSION     :   3, 16-Apr-2003 

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 

 NAME:
	SETUP_ION

 PURPOSE:

	Several of the CHIANTI routines require the atomic data for ions 
       to be read into common blocks, and so this routine performs this 
       task for individual ions.

       Note that the inputs WVLMIN and WVLMAX merely serve to check 
       whether the ion has lines lying in this wavelength range. If yes, 
       then the common blocks are filled with the data; if no, then the 
       common blocks are left empty. 

       An important point to note is that the 
       wgfa and upsilon common blocks contain their data in 2-D array 
       form, suitable for solving the level balance equations. When 
       dealing with dielectronic files, there will be some transitions 
       which will have two A-values, one representing autoionisation 
       rather than radiative decay. For the level balance equations, 
       these two A-values need to be summed together. However, for 
       computing the line emissivity, one needs to only use the radiative 
       decay A-value. For this purpose, the routine outputs the 1-D 
       arrays read by READ_WGFA2 which contain the two separate A-values, 
       allowing other routines to pick out just the radiative decay 
       A-value. These outputs are listed below (LVL1, LVL2, etc.).


 CALLING SEQUENCE:

       SETUP_ION,Ion,Wvlmin,Wvlmax,Wvltst,Lvl1,Lvl2,Wvl1,Gf1,A_value1


 INPUTS

	ION     String specifying ion, e.g., 'c_2'
       
       WVLMIN  Minimum wavelength of interest (angstroms). If there are 
               no lines with wavelengths between WVLMIN and WVLMAX, then 
               no data is read into the common blocks. If both WVLMIN 
               and WVLMAX are set to -1, then no checks are made on the 
               wavelengths (i.e., the common blocks will be filled).

       WVLMAX  Maximum wavelength of interest (angstroms). See above.
	
 OPTIONAL INPUT

       PATH    Can be used to specify a different directory to !xuvtop 
               for the location of the data files. E.g., 
               path='/data/user/chianti/o_4'

 KEYWORDS

       NOPROT  Switches off the inclusion of proton rates.

       ALL     By default the routine only looks for wavelengths which 
               are positive when checking if they lie in the wavelength 
               range. By setting /ALL then negative wavelengths are also 
               included.

 OUTPUTS:

	WVLTST  The number of transitions lying between WVLMIN and WVLMAX. 
               If WVLMIN and WVLMAX are both -1, then WVLTST will 
               be the total number of transitions in the .wgfa file 
               (including any with zero wavelength).

       LVL1    Number of final level of transition (1-D array)

       LVL2    Number of initial level of transition (1-D array)

       WVL1    Wavelenths (in angstroms) of spectral lines formed by this 
               ion (1-D array)

       GF1     Oscillator strength (1-D array)

       A_VALUE1 Radiative transition probability (1-D array)

 OPTIONAL OUTPUTS

       ANYLINES Contains the indices of the elements of lvl1, lvl2, wvl1, 
                gf1, a_value1 arrays for which the wavelengths lie in 
                specified wavelength range.

 EXAMPLE:

    IDL> setup_ion,'c_2',1000.,1500.,wvltst,Lvl1,Lvl2,Wvl1,Gf1,A_value1
    IDL> print,wvltst
          17
    IDL> setup_ion,'c_2',-1,-1,wvltst,Lvl1,Lvl2,Wvl1,Gf1,A_value1
    IDL> print,wvltst
          43
    IDL> setup_ion,'c_2',-1,0,wvltst,Lvl1,Lvl2,Wvl1,Gf1,A_value1
    IDL> print,wvltst
           0

 COMMON BLOCKS:

	common elvlc,l1a,term,conf,ss,ll,jj,ecm,eryd,ecmth,erydth,eref
       common wgfa, wvl,gf,a_value
       common upsilon,t_type,deu,c_ups,splups

 CALLS

    READ_WGFA2, READ_SPLUPS, READ_ELVLC, ION2FILENAME


 MODIFICATION HISTORY:

       Ver.1, Sep-99, Ken Dere
       Ver.2, 10-Oct-00, Peter Young
                Allowed wvlmin and wvlmax to take -1 values.
                Removed elements common block.
                Removed for-loop.
                Added PATH.
       Ver.3, 12-Nov-01, Peter Young
                Added proton common block and /noprot keyword
       Ver.4, 11-Dec-01, Peter Young
                Added keyword /all.

       V.5, Giulio Del Zanna (GDZ)
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

       V.6, 25-Feb-2004, Enrico Landi (EL)
                   Added call to read_ionrec.pro to read ionization 
                   and recombination files.

 VERSION     :   6, 25-Feb-2004, EL 

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME: SHOW_POPS
       
 PURPOSE:

	To display populations of significant levels in a CHIANTI ion 
	model

 CATEGORY:

       Scientific analysis

 EXPLANATION:

	Displays percentage level populations and level IDs for all levels 
	in the specified ion with populations greater than 0.01%. If the 
	temperature is not specified, then it is taken to be where the 
	maximum of the ionisation fraction is.

 CALLING SEQUENCE:

	SHOW_POPS, IZ, ION [, POPSTR, DENS= , TEMP= , /NOPROT,
                           RADTEMP= , RPHOT= , /ALL, /DIEL, PATH=,
                           IONEQ_FILE= , ABUND_FILE= ]

 EXAMPLES:

	show_pops,26,13,popstr
	show_pops,26,13,dens=7.5,temp=6.0,rphot=1.2

 INPUTS:

	IZ	The atomic number of the ion

	ION	The spectroscopic number of the ion (e.g., 12 = XII)

 OPTIONAL INPUTS:

	DENS	Logarithm of electron density

	TEMP	Logarithm of electron temperature. If not specified, then
               T_max of the ion is used

	RADTEMP	Specify background radiation temperature (default: 6000 K)

	RPHOT   Distance from the centre of the star in stellar radius units.
               I.e., RPHOT=1 corresponds to the star's surface. (Default is
               infinity, i.e., no photoexcitation.)

	PATH	Directly specify the path where the ion data is contained, 
		e.g., path='/home/other_data/fe_13'

       N_LEVELS  The size of the ion model is automatically determined 
                 from the information in the CHIANTI data files. Setting 
                 this keyword allows the number of levels in the model to 
                 be reduced. E.g., N_LEVELS=14 reduces the model to the 
                 first 14 levels given in the .ELVLC file.

       IONEQ_FILE To include proton rates in the level balance equations 
                  requires the number of density of protons to be known, 
                  and this requires an ion balance file and an abundance 
                  file to be specified, which are done through the 
                  IONEQ_FILE and ABUND_FILE keywords. If they are not set 
                  then the default files specified by !ioneq_file and 
                  !abund_file are used.

       ABUND_FILE See IONEQ_FILE.

       SUM_MWL_COEFFS  An array of coefficients of the same length as 
                       the array of temperatures. Electron and proton rate 
                       coefficients will be calculated at each temperature 
                       and then a weighted sum of the coefficients is 
                       performed using SUM_MWL_COEFFS. This allows 
                       non-Maxwellian energy distributions to be 
                       incorporated into the level balance equations.
                       If this keyword is set for an ion that has ionization
                       and recombination included in the level balance, then
                       these processes will be switched off for the
                       calculation since their rates implicitly assume a
                       single Maxwellian to describe the ion fractions of
                       the neighbouring ions.

       LEVEL   Allows the control of which level populations are displayed
               to the screen. If set to a positive scalar or array, then
               only those levels are printed. If it is set to a negative
               scalar (-n), then all level populations up to level n are
               printed. E.g., LEVEL=20 (only level 20); LEVEL=[5,7,20]
               (levels 5, 7 and 20); LEVEL=-20 (all levels up to level 20).

       RADFUNC         The name of a user-defined function that will generate
                       a radiation spectrum as a function of temperature. 
                       This radiation field will replace the black-body that
                       is assumed when using the RADTEMP keyword in the call
                       to pop_solver.

; OPTIONAL OUTPUTS

       POPSTR  Send level population information to a structure. POPSTR has 
               the tags:
               .dens    Density (cm^-3)
               .temp    Temperature (K). Can be an array if SUM_MWL_COEFFS=
                        is used.
               .radtemp RADTEMP. Set to -1 if RADTEMP not 
                        set.
               .rphot   RPHOT value. Set to -1 if RPHOT not set.
               .proton  String set to 'yes' if proton rates included, 'no' 
                        otherwise
               .version CHIANTI version used to derive populations.
               .date    Date and time at which structure created.
               .level   Structure containing level information. Tags are:
                  .index   CHIANTI level index
                  .term    String containing level identifier.
                  .pop     Population of level
               .sumtst  Set to 1 if the SUM_MWL_COEFFS keyword has been used.
                        Set to 0 otherwise.
               .sum_mwl_coeffs Contains SUM_MWL_COEFFS. Set to -1 if sumtst=0.

 KEYWORDS:

	ALL	Show populations for all levels.

       NOPROT  If set, then the default setting will be NOT to use 
               proton rates. This can be changed within the routine.

       DIEL    Use the dielectronic recombination files. E.g., for Fe XXII, 
               the routine will read in the fe_22d.* files instead of the 
               fe_22.* files.

 COMMON BLOCKS:

	ELVLC, WGFA, UPSILON, RADIATIVE, PROTON, ELEMENTS

 CALLS:

	ZION2FILENAME, POP_SOLVER, SETUP_ION, READ_IONEQ,
       READ_ABUND, PROTON_DENS, CONCAT_DIR

 HISTORY:

	Ver 1, PRY 22-Sep-97
	Ver.2, PRY 5-Sep-98  - added call to choose_ioneq
	Ver.3, PRY 23-Apr-99 - calls pop_solver now; added DENS keyword
	Ver.4, PRY 18-Dec-99 - added deu to upsilon common block to be 
			consistent with main Chianti routines.
       Ver.5, PRY 7-Aug-00  - added /DIEL keyword to allow populations of 
                       the dielectronic recombination files to be studied.
                       Also changed elvlc common block to match new 
                       version of pop_solver.
       Ver 6, PRY 10-Oct-00 - now calls setup_ion to read ion data
       Ver 7, PRY 12-Nov-01 - modified for proton rates, photoexcitation,
                       and 9 pt splines.
       Ver 8, PRY 9-Dec-01  - completed modifications for v4 of CHIANTI.

       V.  9, 25-May-2002, Giulio Del Zanna (GDZ) 
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 
                   Now we only call zion2filename

       V. 10, 9-Aug-2002, Peter Young
                   corrected !ioneq_file problem

       V. 11, 12-Aug-2002, Peter Young
                   added POPSTR output, and tidied up header.

       V. 12, 4-Oct-2003, GDZ
                  modified the input to POP_SOLVER, now it is dealt with an
                  input structure.

       V 13, 4-May-2005, Enrico Landi (EL)
                  Modified in order to include ionization and recombination
                  data in the input to POP_SOLVER

       V.14, 26-May-2005, Peter Young (implemented by GDZ)
                  added SUM_MWL_COEFFS optional input for allowing
                  non-Maxwellian distributions to be considered.

                  added LEVEL= optional input to only print the populations of
                  a few levels.

       V.15, 5-Jul-2005, Peter Young
                  added RADFUNC= and /QUIET keywords

 VERSION     :   15, 5-Jul-2005

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	SPECTROSCOPIC2ION

 PURPOSE:
	provide identification string

 CATEGORY:

	database.

 CALLING SEQUENCE:

       SPECTROSCOPIC2ION,  snote, Ion, dielectronic=dielectronic

 INPUTS:

	snote:  the spectroscopic notation for the ion, i.e. 'C II'

 OPTIONAL INPUTS: none

 KEYWORD PARAMETERS:
              
 OUTPUTS:
       Ion:   CHIANTI notation for an ion, i.e., 'c_2' for C II	

 OPTIONAL OUTPUTS:  dielectronic (0/1)

 EXAMPLE:
             > spectroscopic2ion, 'O VI d', ion,dielectronic=dielectronic
             > help, ion, dielectronic
             > ION             STRING    = 'o_6d'
             > DIELECTRONIC    INT       =        1

 WRITTEN     : 
       Version 1, Written by: Giulio Del Zanna (GDZ) 25-May-2002

 MODIFICATION HISTORY:

       V.2, 12-Aug-02, GDZ 
           Corrected a typo concerning XXII.

 VERSION     :   2, 12-Aug-02

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 

 NAME:
	SUTHERLAND

 PURPOSE:

	Calculate the free-free continuum from an hot, low density plasma

       Uses the free-free gaunt factor calculations of Sutherland, 1998, 
       MNRAS, 300, 321.

       Note that Sutherland's Eq.(15) has units of erg/cm^3/s. Comparing 
       with Rybicki & Lightman's Eq.5.14(a) (in their book 'Radiative 
       Processes in Astrophysics'), suggests that Sutherland's units 
       should be erg/cm^3/s/sr/Hz. We are assuming the latter to be 
       correct in this routine.

       When using the DEM_INT optional input, FREEFREE expects the 
       differential emission measure to have been derived from a product 
       of N_e*N_H rather than N_e*N_e. This can be important when dealing 
       with a regime (typically T < 10^4.5) where H and He are not fully 
       ionised.

 CALLING SEQUENCE:

       SUTHERLAND,temperature, wavelength, intensity


 INPUTS:

	T	   Temperature in degrees Kelvin, can be a 1 D array
       WVL        Wavelength in Angstroms


 OPTIONAL INPUTS:

	None
	
 KEYWORD PARAMETERS:

	NO_SETUP:  If the procedure setup_elements has already been called 
                  then the keyword /no_setup should be set to avoid 
                  repeating this step.

       MIN_ABUND: If set, calculates the continuum only from those 
                  elements which have an abundance greater than min_abund.  
                  This can speed up the calculations. ;

	DEM_INT    The intensity array is multiplied by a DEM number for 
                  each temperature. DEM_INT needs to be of the same size 
                  as TEMPERATURE. It is needed for the synthetic spectrum 
                  routines.

       PHOTONS    The output spectrum is given in photon units rather 
                  than ergs.

       SUMT       The default is to output the intensity array as an array 
                  of size (nwvl x nT). Setting this keyword performs a sum 
                  over the temperatures to yield a vector of same size as 
                  the input wavelengths, thus producing the complete 
                  free-free spectrum.
	
 OUTPUTS:

	RAD        Free-free continuum intensity in units
                  10^-40 erg cm^3 s^-1 str^-1 angstrom^-1 per unit 
                  emission measure [ integral (N_e N_H dh) in cm^-5 ]. 
                  If T is given as a 1-D array, then RAD will be output 
                  as a 2-D array, with one element for each temperature 
                  and wavelength (but also see SUMT).


 PROGRAMMING NOTES

     The gaunt factors from Sutherland (MNRAS 300, 321, 1998) are a 
     function of uu and gg (see his Eq. 14). uu is a function of both 
     wavelength and T, while gg is a function of T only.

     The gaunt factor (gff) is tabulated for values of uu and gg at 
     fixed intervals in log(uu) and log(gg). The log(uu) values go from 
     -4 to 4 in 0.2 steps; the log(gg) values go from -4 to 4 in 0.1 steps.

     A particular (input) temperature and wavelength give rise to values 
     uu0 and gg0, the logs of which lie between -4 and 4. To derive the 
     corresponding gff0 value, I use the IDL routine BILINEAR. 

     BILINEAR requires, not uu and gg values as input, but indices. 
     E.g., the indices corresponding to the tabulated values of uu are 
     0 (=-4.0), 1 (=-3.8), 2 (=-3.6), etc. Thus, if log(uu0)=-3.76, then 
     i_uu0=1.20 is the index of uu0.

     In order to make significant time-savings, I give BILINEAR all of 
     the wavelengths and temperatures in the same call for a particular 
     ion. To do this, I make my i_uu and i_gg values 2-D arrays of size 
     (nwvl x nT), and BILINEAR then produces a (nwvl x nT) array 
     containing the gff values.

     A problem occurred if nT=1, as BILINEAR will turn the input uu and 
     gg vectors into 2-D arrays of size (nwvl x nwvl). If there are a 
     large number of wavelengths, this uses a lot of memory. To solve 
     this I make a 2 element temperature vector whose values are 
     identical, and then change this back to a 1 element vector after 
     BILINEAR has been called. See the parts of the code where I use 
     'tst1'.


 COMMON BLOCKS:

	common elements,abund,abund_ref,ioneq,ioneq_t,ioneq_ref

 CALLS

       READ_IP, READ_GFFGU, SETUP_ELEMENTS

 EXAMPLES:

       IDL> freefree,1.e+6,wvl,int
       IDL> freefree,1.e+6,wvl,int,min_abund=3.e-5
       IDL> freefree,1.e+6,wvl,int,/no_setup,min_abund=1.e-6

       IDL> wvl=findgen(5001)/10. + 50.
       IDL> temp=10.^(findgen(41)/10. +4.)
       IDL> freefree,temp,wvl,int


 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	March 1999:     Version 2.0
       September 1999:  Version 3.0

       Ver.3.1, 11-Aug-00, Peter Young
           Improved call to bilinear, allowing routine to solve for 
           all temperatures in one go. This makes the routine quicker, 
           and also lowers the memory usage of the routine when dealing 
           with many wavelengths.

       Ver.3.2, 16-Aug-00, Peter Young
           Corrected expression for 'gg', replacing ip with z^2.

       Ver.3.3, 16-Oct-00, Peter Young
           Now deals with dem_int correctly

       Ver.3.4, 10-Oct-01, Ken Dere
           Corrected for labelling errors in Sutherland's gffgu.dat file
           No longer reads ionization potential file

       Ver.3.5, 5-Dec-01, Peter Young
           Corrected expression for gamma^2
           Renamed routine sutherland.pro
           Restructured code to make it run quicker.

       Ver.3.6, 22-May-01, Peter Young
           Re-instated the MIN_ABUND optional input. 
           Changed ioneq_t to ioneq_logt (GDZ).

       Ver.3.7, 18-Aug-03, Peter Young
           Activated /PHOTONS keyword

       Ver.3.8, 5-Nov-03, Peter Young
           Corrected bug found by Jim McTiernan when multiple temperatures
           were input. The quantity 'newfactor' was not being calculated
           correctly due to indexing problems.

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	SYNTHETIC

 PURPOSE:

       calculates a synthetic spectrum


 PROCEDURE:

                 Calculations are done assuming either constant density or
                 constant pressure. See CH_SYNTHETIC for details.


 CALLING SEQUENCE:

       SYNTHETIC,Wmin, Wmax, Fwhm, Pressure= , Lambda, Spectrum ,List_wvl, List_ident
                 ,[/all, density=, /cont, min_abund=]


 INPUTS:


	Wmin:   lower limit of the wavelength/energy range of interest (Angstroms)

	Wmax:   upper limit of the wavelength/energy range of interest (Angstroms)

       Pressure:  pressure in emitting region (cm^-3 K), or 
       Density:   density in emitting region (cm^-3).

       Fwhm:  gaussian full width at half maximum of the resolution of the output 
                  spectrum, for example, to correspond to an observed spectrum


 OPTIONAL INPUTS:

	SNGL_ION:  specifies  a single ion (e.g. SNGL_ION='Fe_10' to include
                 only Fe X lines) or an array (e.g. SNGL_ION=['Fe_10','Fe_11']
                 to include only Fe X and Fe XI lines) of ions to be used
                 instead of the complete set of ions specified in
                 !xuvtop/masterlist/masterlist.ions 

       MASTERLIST: string of a specific masterlist file (full path). 
                   If defined as a keyword (i.e. MASTERLIST=1 or /MASTERLIST)
                   then a widget allows the user to select a  user-defined
                   masterlist file. Shortcut for SNGL_ION.   


       MIN_ABUND:  If set, calculates the continuum only from those elements which 
                   have an abundance greater than min_abund. 

	DEM_NAME:  Name of the DEM file to used.  If not passed, then the user
		   is prompted for it.

	ABUND_NAME:  Name of the abundance file to use.  If not passed, then
		     the user is prompted for it.

	IONEQ_NAME:  Name of the ionization equilization name to use.  If not
		     passed, then the user is prompted for it.

       RPHOT   Distance from the centre of the star in stellar radius units.
               I.e., RPHOT=1 corresponds to the star's surface. (Default is
               infinity, i.e., no photoexcitation.)

       RADTEMP The blackbody radiation field temperature (default 6000 K).
 

 OUTPUTS:

       Lambda:  wavelength array of calculated synthetic spectrum
       Spectrum:  intensity array (erg cm^-2 s^-1 str^-1 Ang^-1),
                  unless keyword photons is set then output is is
                  photons cm^-2 s^-1 str^-1 Ang^-1
       List_wvl:  a list of wavelengths for use with synthetic_plot.pro
       List_ident:  a list of line identifications for use with 
                        synthetic_plot.pro

 OPTIONAL OUTPUTS:

	
 KEYWORD PARAMETERS:

     
	ALL:  if set, then all lines are included.  This means that lines for which
             only an approximate wavelength is known (only theoretical energy
             levels are known) are included.

	SNGL_ION:  specifies  a single ion (e.g. SNGL_ION='Fe_10' to include
                 only Fe X lines) or an array (e.g. SNGL_ION=['Fe_10','Fe_11']
                 to include only Fe X and Fe XI lines) of ions to be used
                 instead of the complete set of ions specified in
                 !xuvtop/masterlist/masterlist.ions 

       MASTERLIST: string of a specific masterlist file (full path). 
                   If defined as a keyword (i.e. MASTERLIST=1 or /MASTERLIST)
                   then a widget allows the user to select a  user-defined
                   masterlist file. Shortcut for SNGL_ION.   

       CONTINUUM:   if set, then the continuum (free-free, free-bound and
                  two-photon) are  included 

       MIN_ABUND:  If set, calculates the continuum only from those elements which 
                   have an abundance greater than min_abund.  Can speed up the 
                   calculations.  For example, from Allen (1973):
                   abundance (H)  = 1.
                   abundance (He) = 0.085
                   abundance (C)  = 3.3e-4
                   abundance (O)  = 6.6e-4
                   abundance (Si) = 3.3e-5
                   abundance (Fe) = 3.9e-5



	PHOTONS:  if set, intensities are in photons cm^-2 s^-1 sr^-1 Ang^-1

	DEM_NAME:  Name of the DEM file to used.  If not passed, then the user
		   is prompted for it.

	ABUND_NAME:  Name of the abundance file to use.  If not passed, then
		     the user is prompted for it.

	IONEQ_NAME:  Name of the ionization equilization name to use.  If not
		     passed, then the user is prompted for it.

       NOPROT   If set, then proton rates are not included.

	RADTEMP	Specify background radiation temperature (default: 6000 K)

	RPHOT   Distance from the centre of the star in stellar radius units.
               I.e., RPHOT=1 corresponds to the star's surface. (Default is
               infinity, i.e., no photoexcitation.)

 CALLS:
       
       CH_SYNTHETIC, MAKE_CHIANTI_SPEC, READ_ABUND, STRPAD


 COMMON BLOCKS: None


 RESTRICTIONS:

 SIDE EFFECTS:


 EXAMPLE:

       > synthetic,100.,200.,.1, pressure=1.e+16,lambda,spectrum,list_wvl,list_ident


 CATEGORY:

	spectral synthesis.

 WRITTEN     : 

       Version 1, 8-Nov-01, Giulio Del Zanna (GDZ). 

       Rewritten as a wrapper routine using the new procedures.

       Compared to the previous SYNTHETIC, these are the main changes:

       1-Now the PRESSURE value is a keyword as the DENSITY value
       2-The keyword CONT is now renamed CONTINUUM
       3-Added keywords PHOTONS, DEM_NAME, ABUND_NAME, IONEQ_NAME
       4-MASTERLIST can now be used both as an input string or as a keyword.
       5-The description of the line details now has the spectroscopic 
         designation at the end.


 MODIFICATION HISTORY:

       Version 2, 18-Nov-01, Peter Young
           Added /noprot, rphot and radtemp keywords.

       Version 3, 11-Dec-01, Peter Young
           Changed call to ch_strpad to strpad.

       Version 4, 28-Apr-02, GDZ, changed the call to make_chianti_spec and the
       continuum keyword.

       V. 5, 22-May-2002 GDZ.  Removed const_net definitions.

       V.6, 14-Feb-2003 GDZ.
             Fixed a bug (keyword PHOTONS was not active). 
             
 VERSION     : 6, 14-Feb-2003

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 

 NAME:
	synthetic_plot

 PURPOSE:

       to plot out synthetic spectra calculated with Synthetic
       and interactively identify spectral lines


 CATEGORY:
	
	spectroscopy

 CALLING SEQUENCE:

       SYNTHETIC_PLOT,Wvl,Spectrum,List_wvl,List_ident,fwhm


 INPUTS:

       Wvl:  wavelength array from synthetic
       Spectrum:  spectrum intensity array from synthetic
       List_wvl:  string array of spectral line wavelengths
       List_ident:  string array of spectral line identifications
       Fwhm:  when the cursor is clicked, spectral lines with fwhm
              (Angstroms) of the cursor are printed out


 KEYWORDS

	xrange:  similar to IDL keyword to determine wavelength range of plot

 OUTPUTS:

       None


 PROCEDURE:

	Click the left mouse button to select a wavelength
       Click the right mouse button to exit

 EXAMPLE:

      > synthetic,100.,200.,.1,1.e+15,wvl,spectrum,list_wvl,list_ident
      > synthetic_plot,wvl,spectrum,list_wvl,list_ident,0.1
                     
      note:  it is not necessary for the two fwhm values to be the same      

 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	May 1996:     Version 2.0
       Dec. 1998:    revised by Ken Dere
       V.4,  23 Oct 2000 GDZ, added the log keyword, and changed a few things
       in the plot. 

       Ver.5, 12-Dec-2001, Peter Young
           Changed style of printing, and made method of extracting the 
           intensity from list_ident compatible with the new version of 
           isothermal.pro.

 VERSION 5   12 Dec 2001 Peter Young

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	TEMPERATURE_RATIOS

 PURPOSE:

	calculate and display temperature sensitivity of line intensity ratios

 CATEGORY:

	spectral diagnostics

 PROCEDURE :

       The intensities (Population of the upper level * A)  of the lines within
       the selected ion are first  calculated, either at constant pressure or
       at constant density (however specified in the input). They are plotted
       in window 0. The intensities  relative to the brightest  reference line
       are then plotted in window 1. A widget allows the user to select a
       number of lines (at least one!) for the numerator of the ratio, and a
       number of lines for the denominator. In case of multiple selections, the
       line intensities are summed. The ratio values are plotted in window 2, and
       optionally also saved in a text file. A postscript file can also be
       created. The ratio values, calculated at twice and half the prescribed
       density  are also calculated and overplotted, to show how the
       temperature ratio also depends on the density.

 CALLING SEQUENCE:


      > temperature_ratios,ion,wmin,wmax,Log10(tempmin),Log10(tempmax),temperature,ratio,description,$
       [pressure= ,density= , psfile= , outfile= ]


 EXAMPLE:

      > temperature_ratios,'c_4',100.,1600.,4.,6.,temp,ratio,desc,density=1.e+10,$ 
        psfile='test.ps', outfile='test.txt'

       then select  the  ratio of (384.17 + 384.19) to 1550.772



 INPUTS:

       Ion:   the CHIANTI style name of the ion, i.e., 'c_5' for C V

       Wmin:  minimum  wavelength  limit in Angstroms

       Wmax:  maximum  wavelength  limit in Angstroms

       Tempmin:  log10 of lowest temperature of interest, i.e. 4 for 10.^4 K

       Tempmax:  log10 of highest temperature of interest

 OPTIONAL INPUTS:

	Must specify indices of lines which are to form the ratio
	
       RADTEMP   The blackbody radiation field temperature (default 
                 6000 K).

       RPHOT     Distance from the centre of the star in stellar radius 
                 units. I.e., RPHOT=1 corresponds to the star's surface. 
                 (Default is infinity, i.e., no photoexcitation.)

       ABUND_FILE  The name of a CHIANTI abundance file. This is used for 
                 calculating the proton to electron ratio. Default is 
                 !abund_file.

       IONEQ_FILE  The name of a CHIANTI ion balance file. This is used for 
                 calculating the proton to electron ratio and evaluating 
                 the T_max of the ion. Default is !ioneq_file.

 OUTPUTS:

	Temperature:  an array of temperatures spanning Tempmin to Tempmax

       Ratio:  an array of the intensity ratio of the selected lines

       Desc:  a short string description of the selected line ratio


 OPTIONAL OUTPUTS:

	Ps and/or  text file with the  intensity ratio.


 KEYWORD PARAMETERS:

		
	DENSITY:  calculates the intensity ratios for constant density.

                  If neither density or pressure are specified, a constant
                  density of 1.e+10 cm^-3 is assumed as default.

       OUTFILE:  the (optional) name of the output ascii file where a 
                   listing of the line ratio intensities as a function of 
                   temperature is saved.

       PSFILE:  the (optional) name of the output postscript file 
                  where a plot of the chosen temperature sensitive line
                  ratio is saved.

       NOPROT    Switches off inclusion of proton rates.

       VERBOSE   prints out information

 CALLS: 

        read_ioneq, convertname, ion2spectroscopic,ion2filename,
        ch_xmenu_sel, emiss_calc

 COMMON:

       elvlc,l1a,term,conf,ss,ll,jj,ecm,eryd,ecmth,erydth,eref
       wgfa, wvl,gf,a_value
       upsilon,t_type,deu,c_ups,splups
       proton, pstr, pe_ratio
       radiative, radt, dilute

 RESTRICTIONS:

               
 SIDE EFFECTS: None known yet.
                 

 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	May 1996:     Version 2.0, Ken Dere
       April 2000:   V. 3 Ken Dere modified for V3
       14-Jul-2000   V. 4  Peter Young, now calls pop_solver
        2-Oct-2000   V. 5 Giulio Del Zanna, corrected an error in the 
             creation of the string list of the lines in the ratio. 
             Also corrected a few minor errors.
             Removed the device,window_state call, and added a few 
             other 'cosmetic' adjustments.  
	Version 6, 21-Dec-2000, William Thompson
	      Modified for better cross-platform capability.

       Ver.7, 6-Dec-2001, Peter Young
             Revised to call emiss_calc for the emissivities.

       V.8, 21-May-2002, GDZ 
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 

       V.9, 1-Aug-02 GDZ
          Fixed label mistake, and changed all the formats.

       V.10, 06-Aug-02 GDZ
              Changed the use of CHIANTI system variables. 

       V.11, 15-Aug-02, GDZ 
              Major revision:
              -Added the keyword VERBOSE, to avoid printing out long lists of lines.
              -Removed the call to ch_xselect_s, that did not work for long lists.
              -Added a '*' in the line lists, to identify 'unobserved' lines.
              -Replaced the commands to create PS file, to make it
               cross-platform compatible.
              -Added a large number of cosmetics, mainly lables to the axes and
               titles, that were missing.
              -Removed plotting in windows already present.
              -Removed the pressure keyword.
              -Added the CHIANTI version number in the outputs.

        V.12, 3-Nov-03  GDZ
           Modified format e8.2 to e9.2 for Windows compatibility.

 VERSION     :   12, 3-Nov-03

 PROJECT

       CHIANTI   http://wwwsolar.nrl.navy.mil/chianti.html

       CHIANTI is an atomic database package for the calculation of
       continuum and emission line spectra from astrophysical plasmas. It is a 
       collaborative project involving the Naval Research Laboratory
       (Washington DC, USA), the Arcetri Observatory (Firenze, Italy), and the
       Cambridge University (United Kingdom).

 NAME
        temp_plotter

 PURPOSE:
        A widget-based routine to allow the analysis of temperature sensitive
        ratios. **** See RATIO_PLOTTER for details. *****

 CALLING SEQUENCE:

       IDL>  temp_plotter,  name,$ 
                  EM, PATH=PATH, NOPROT=NOPROT, $
                  IONEQ_FILE=IONEQ_FILE, ABUND_FILE=ABUND_FILE


 INPUTS:
        The ion name (e.g. 'si_3' for Si III)

 OPTIONAL INPUTS : none

 OUTPUTS:

 OPTIONAL OUTPUTS:

	EM:	Save the displayed emissivities to structure EM.
               **** See RATIO_PLOTTER for details. *****

 KEYWORDS:


	PATH:	Data in the CHIANTI format that is not in the CHIANTI 
		database can be read by specifying the directory in which 
		it lies through PATH.

       ABUND_FILE  The name of a CHIANTI abundance file. This is used for 
               calculating the proton to electron ratio. Default is 
               !abund_file.

       IONEQ_FILE  The name of a CHIANTI ion balance file. This is used for 
               calculating the proton to electron ratio and evaluating 
               the T_max of the ion. Default is !ioneq_file.

       NOPROT  If set, then the default setting will be NOT to use 
               proton rates. This can be changed within the routine.


 CALLS:   CONVERTNAME RATIO_PLOTTER
      

 COMMON BLOCKS: none


 RESTRICTIONS:

 SIDE EFFECTS:

 CATEGORY:
	spectral synthesis.
	
 EXAMPLE:
             IDL> temp_plotter, 'fe_13'

 WRITTEN     : 
              Ver.1, 18-Apr-2002, Giulio Del Zanna (GDZ) written as a wrapper
              routine to call RATIO_PLOTTER (written by P. Young).

 MODIFIED:   V.2,  2-Aug-2005, GDZ
              Now the routine handles the dielectronic case


 VERSION     :   2,  2-Aug-2005

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	TWO_PHOTON

 PURPOSE:

	Calculate the 2 photon continuum from a hot, low density plasma.

       For the hydrogen isoelectronic sequence, A values
             Parpia, F. A., and Johnson, W. R., 1982, Phys. Rev. A, 26, 1142.
       and distribution function as a function of Z is taken from: 
             Goldman, S.P. and Drake, G.W.F., 1981, Phys Rev A, 24, 183

       For the helium isoelectronic sequence, A values are from:
             Drake, G.W.F., 1986, Phys. Rev. A, 34, 2871
       and the distribution function as a function of Z is taken from:
             Drake, G.W.F., Victor, G.A., Dalgarno, A., 1969, Phys. 
             Rev. A, 180, 25.
       in this paper the distribution is only given up to Z=10 but  
       extrapolation to higher Z appears to be OK.

       Note that, unlike the freefree and freebound routines, two_photon 
       requies the electron density to be specified. This is because there 
       is a call to pop_solver

 CALLING SEQUENCE:

       TWO_PHOTON,temperature, density, wavelength, intensity


 INPUTS:

	TEMPERATURE   Temperature in degrees Kelvin, can be a 1D array

       WAVELENGTH    Wavelengths in Angstroms.


 OPTIONAL INPUTS:

       DENSITY       Electron density in cm^-3, can also be a 1D array 
                     of the same size as Temperature. If there are several 
                     temperatures specified but only one density, then 
                     density is assumed the same at all temperatures.
                     If not specified, then default densities of 10^10 
                     electrons/cm^3 are assumed.

       DEM_INT An array of same length as TEMP which contains the 
               differential emission measure values at each temperature. 
               The emissivity at each temperature is multiplied by the 
               DEM value and the d(logT) value.
	
 KEYWORD PARAMETERS:

	NO_SETUP:   If the procedure setup_elements has already been called 
                   then the keyword /no_setup should be set to avoid 
                   repeating this step

       MIN_ABUND:  If set, calculates the continuum only from those 
                   elements which have an abundance greater than min_abund.  
                   Can speed up the 
                   calculations.  For example:
                   abundance (H)  = 1.
                   abundance (He) = 0.085
                   abundance (C)  = 3.3e-4
                   abundance (Si) = 3.3e-5
                   abundance (Fe) = 3.9e-5

       SUMT        If several temperatures have been specified, then /sumt 
                   will sum the emissivities over the different 
                   temperatures, giving an output INTENSITY that has the 
                   same size as WAVELENGTH.

       PHOTONS     If set the continuum emissivity is output in photon 
                   units rather than erg units.

       VERBOSE
 
 OUTPUTS:

	RAD         2 photon continuum intensity in units of
                   10^-40 erg cm^3/s/sr/Angstrom  per unit emission measure 
                   ( integral(N_H N_e dh) in cm^-5) if a DEM is not defined. 

                   If DEM values are defined, it is assumed that they are given
                   as N_H N_e dh/dT.  The units are 
                   10^-40 erg/cm^2/s/sr/Angstrom 

            If T is given as a 1-D array, then the output will be a 2-D array,
            with one element for each temperature and wavelength 
            (but also see SUMT).



 CALLS

       POP_SOLVER, SETUP_ION, SETUP_ELEMENTS, READ_MASTERLIST,
       CONVERTNAME

 COMMON BLOCKS:

       ELEMENTS, ELVLC, WGFA, UPSILON, PROTON

 EXAMPLE:

             > two_photon,1.e+6,3.e+10,wvl,int
             > two_photon,1.e+6,3.e+10,wvl,int,min_abund=3.e-5
             > two_photon,1.e+6,3.e+10,wvl,int,/no_setup

 PROGRAMMING NOTES

    For He 2-photon decays, the distribution function is from Table II 
    of Drake et al. (1969), except that the values have been divided by 
    the A-value from Drake (1986).


 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	February 2001:  Version 1.0

       Ver.2, 19-Dec-2001, Peter Young
           Now allows an array of temperatures.
           Added /SUMT keyword.
           Added DEM_INT= optional input.
           Switched to using spl_init & spl_interp for the spline fits.
           Corrected a small bug.

       Ver.3, 20-Dec-2001, Peter Young
           Corrected a bug related to density indices.

       Ver.4, 23-Apr-2002, Peter Young
           Added /photons keyword.

       Ver.5, 28-May-2002, Peter Young
           Corrected way in which DEM_INT is handled.

       V. 6, 28-May-2002, Giulio Del Zanna (GDZ)
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. 
             Corrected the description of the  units and various
             inaccuracies in the header.
    
       V.7, 14-Aug-02, GDZ
             Added keyword VERBOSE

       V.8,  4-Oct-2003, GDZ
                  modified the input to POP_SOLVER, now it is dealt with an
                  input structure.

       V.9,  8-Jun-2004, EL
                  modified the input to POP_SOLVER, now it includes ion/rec

       V.10, 5-Jul-2005
                  corrected problems with the input structure for pop_solver

       v.11 29-Jul-2005, GDZ
                  fixed bug, only define ioneq_ionrec when files are
                  there (it was failing with neutrals)

 VERSION     :   11 29-Jul-2005

 Project     : CHIANTI

       CHIANTI is an atomic database package for the calculation of
       continuum and emission line spectra from astrophysical plasmas. It is a 
       collaborative project involving the Naval Research Laboratory
       (Washington DC, USA), the Arcetri Observatory (Firenze, Italy), and the
       Cambridge University (United Kingdom).
 
                   
 Name        : USE_CHIANTI
               
 Purpose     : Sets up system variables for use of CHIANTI routines
               
 Explanation : The  CHIANTI software uses system variables
               that have to be defined. This routine is called by the 
               CHIANTI routines if these system variables are not defined.

               ** If one is using the solar-soft package, these should 
               already be defined*****.

               ** If the CHIANTI package is used as stand-alone, then 
               this routine can be used for the setup with e.g.:

               use_chianti,'/home/data/chianti/'

               if /home/data/chianti/ points to the actual place where 
               the CHIANTI top directory is.

               
 Use         : IDL> use_chianti, '/home/data/chianti/', $
                                 [ioneq= , abund=]
    
 Inputs      : None
               
 Opt. Inputs : The full pathname of the CHIANTI top directory.
               
 Outputs     : None
               
 Opt. Outputs: None
               
 Keywords    : IONEQ  - to define the default ionization eq. file to be used.
               ABUND  -  to define the default abundance file to be used.

 Calls       : None

 Common      : None
               
 Restrictions: None
               
 Side effects: None
               
 Category    : 
               
 Prev. Hist. : Based on use_dere_chianti, written by C D Pike, RAL

 Written     : Giulio Del Zanna (GDZ)  DAMTP  (University of Cambridge, UK) 
               
 Modified    : Version 1, GDZ 10-Oct-2000
               Version 2, GDZ 10-Jan-2001
               added the definition of the !abund_file

               V. 3, GDZ, 2-May-2002 Modified substantially, adding a new
               system variable.

               V.4, 10-July-2002 GDZ
                 Removed the definition of !chianti_top, upon request.

               V.5, 25-July-2002, GDZ 
                Fixed a problem with IDL versions earlier than 5.3 (the routine
                would not compile). ALso, introduced the use of concat_dir for
                cross-platform compatibility.
                    
               V.6, 06-Aug-02 GDZ
                 Changed the use of CHIANTI system variables. Added comments on
                 the which CHIANTI version is used.
               V.7 12-Aug-02 GDZ Changed default abundance file. Removed '***'
               V.8, GDZ 13-Feb-2003
                   Changed default ioneq  file, to include ALL the elements.

               V.9,  12-Aug-2005, GDZ 
                   Changed default ioneq file from mazzotta_etal_ext to 
                   mazzotta_etal_9.ioneq where ion fractions have been extended
                   up to 10^9 K. This is useful to avoid steps in the
                   emissivities at high-temperatures.


 Version     : V.9,  12-Aug-2005

 PROJECT:  CHIANTI

      CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
      Astrophysical Plasmas. It is a collaborative project involving the Naval
      Research Laboratory (USA), the University of Florence (Italy), the
      University of Cambridge and the Rutherford Appleton Laboratory (UK). 

 NAME

    VERNER_XS()

 EXPLANATION

    Reads the Verner & Yakovlev (A&AS 109, 125, 1995) photoionization 
    cross-section data and generates the values of the cross-section at 
    the wavelengths WVL

 INPUTS

    IZ     Atomic number of ion (e.g., 26 = Fe)

    ION    Spectroscopic number of ion (e.g., 13 = XIII)

    WVL    Wavelengths (in angstroms) for which cross-sections are 
           required (1-D array).

 OPTIONAL INPUTS

    DATA   By default VERNER_XS reads the Verner & Yakovlev data file when 
           it is called. Through the DATA keyword the data array can be 
           sent to VERNER_XS instead.

 OUTPUT

    The photoionization cross-section for the ionization of the outer 
    electron in units of mega-barns (Mb = 10^-18 cm^2) at the input 
    wavelengths. E.g., for Fe XIII (ground configuration 
    1s2.2s2.2p6.3s2.3p2) it is the cross-section for the removal of the 
    3p electron.

 HISTORY

    Ver.1, 24-Jul-2002, Peter Young

 NAME

     W2R()

 EXPLANATION

     Converts a dilution factor into a distance above a star.

 INPUTS

     W     Radiation dilution factor.

 OUTPUT

     Distance from star -- a number greater than 1.

 HISTORY

     Ver.1, 7-Dec-2001, Peter Young

 CONTACT

     Peter Young, CfA, pyoung@cfa.harvard.edu

 NAME

     WHICH_LINE

 PROJECT

     CHIANTI

 PURPOSE:

     Upon given an ion name and wavelength, this routine prints out a list
     of possible line IDs for the wavelength. Wavelengths within 1% of the
     input wavelength are searched for.

 INPUTS

     IONNAME  Name of an ion in the CHIANTI format. E.g., 'fe_13' for Fe XIII.

     WVL      A wavelength in angstroms.

 OUTPUTS (to screen)

     Prints a list of atomic transitions and wavelengths for lines close to
     the input wavelength. A '*' is placed next to the closest wavelength
     match.

 KEYWORDS

     NARROW   Narrows the search range to 0.02% of the specified wavelength.

 EXAMPLE

     IDL> which_line,'o_6',1032
     Wavelength   i   j Lower level           Upper level             A-value
       1037.615   1   2 1s2.2s 2S1/2        - 1s2.2p 2P1/2          4.21e+008
       1031.914   1   3 1s2.2s 2S1/2        - 1s2.2p 2P3/2          4.28e+008

 CALLS

     CONVERTNAME, ZION2FILENAME, READ_WGFA2, READ_ELVLC

 HISTORY

     Ver.1, 22-Jun-2004, Peter Young

 PROJECT:  CHIANTI

       CHIANTI is an atomic database package for the calculation of
       continuum and emission line spectra from astrophysical plasmas. It is a 
       collaborative project involving the Naval Research Laboratory
       (Washington DC, USA), the Arcetri Observatory (Firenze, Italy), and the
       Cambridge University (United Kingdom).


 NAME:
	Z2ELEMENT

 PURPOSE:


	provide identification strings

 CATEGORY:

	database.

 CALLING SEQUENCE:

       Z2ELEMENT, Iz, Name


 INPUTS:

	Iz:  nuclear charge of ion of interest, i.e. 26 for Fe


 OUTPUTS:

	Name:  a string identifying the element



 EXAMPLE:

             > z2element,2,name
             > print,name
             > He  

 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	March 1996:     Version 2.0

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	ZION2FILENAME

 PURPOSE:

	help locate CHIANTI database files

 CATEGORY:

	database.

 CALLING SEQUENCE:

       ZION2FILENAME, Iz, Ion, Filename


 INPUTS:

	Iz:  nuclear charge of ion of interest, i.e. 26 for Fe
       Ion:   charge state of ion of interest, i.e. 2 for Fe II	

  KEYWORDS:
       
       diel:  set if excitation of this ion is by dielectronic
		recombination

 OUTPUTS:

	Filename:  the complete filename and path specification for generic
                  CHIANTI database file, i.e. '.elvlc' suffix is not included


 RESTRICTIONS:

	!xuvtop must be set


 EXAMPLE:

             > zion2filename,26,2,filename
             > print,filename
             > /data1/xuv/fe/fe_2/fe_2   assuming !xuvtop = '/data1/xuv'

 MODIFICATION HISTORY:
 	Written by:	Ken Dere
	March 1996:     Version 2.0
       Sept  1996:     Modified for use with VMS
       December 1998:  Modified to diel keyword

       V.5, 29-May-2002, Giulio Del Zanna (GDZ) 
                   generalized directory concatenation to work for
                   Unix, Windows  and VMS. Added keyword name to output just
                   the name of the file and changed the dielectronic  keyword. 

 VERSION     :   5, 29-May-2002 

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics of
       Astrophysical Plasmas. It is a collaborative project involving the Naval
       Research Laboratory (USA), the University of Florence (Italy), the
       University of Cambridge and the Rutherford Appleton Laboratory (UK). 


 NAME:
	ZION2SPECTROSCOPIC

 PURPOSE:


	provide identification strings

 CATEGORY:

	database.

 CALLING SEQUENCE:

       ZION2SPECTROSCOPIC, Iz, Ion, Name


 INPUTS:

	Iz:  nuclear charge of ion of interest, i.e. 26 for Fe
       Ion:   charge state of ion of interest, i.e. 2 for Fe II	


 OUTPUTS:

	Name:  the spectroscopic notation for the ion, i.e. 'Fe II'



 EXAMPLE:

             > zion2spectroscopic,26,2,name
             > print,name
             > Fe II   

 WRITTEN     :  Ken Dere

 MODIFICATION HISTORY:

	March 1996:     Version 2.0

       V.3, 25-May-2002, Giulio Del Zanna (GDZ)
            added the DIELECTRONIC keyword.

 VERSION     : 3, 25-May-2002

 NAME:

      CHIANTI_FONT

 PURPOSE:

      Generates standard fonts for CHIANTI GUIs suitable for both Unix and
      Windows operating systems.

 CATEGORY:

      Widgets, fonts

 CALLING SEQUENCE:

      CHIANTI_FONT, FONT [, /BIG, /FIXED ]

 INPUTS:

      None.

 OPTIONAL INPUTS:

      None.

 KEYWORD PARAMETERS:

      BIG    Output a descriptor for a large font.

      FIXED  Output a descriptor for a fixed-width font.

 OUTPUTS:

      FONT   A descriptor for a font suitable for passing to IDL widget
             routines.

 OPTIONAL OUTPUTS:

      None.

 COMMON BLOCKS:

      None.

 SIDE EFFECTS:

      None.

 RESTRICTIONS:

      Has not been tried with a MAC OS.

 PROCEDURE:

      CHIANTI_FONT, FONT [, /BIG, /FIXED ]

 EXAMPLE:

      IDL> chianti_font,font
      IDL> print,font
      Arial*bold*16

 MODIFICATION HISTORY:

      Ver.1, 6-Aug-2003, Peter Young

 PROJECT:  CHIANTI

       CHIANTI is an Atomic Database Package for Spectroscopic Diagnostics 
       of Astrophysical Plasmas. It is a collaborative project involving 
       the Naval Research Laboratory (USA), the University of Florence 
       (Italy), the University of Cambridge and the Rutherford Appleton 
       Laboratory (UK). 

 NAME:

       FB_RAD_LOSS

 PURPOSE:

       Calculate the total radiative losses of a plasma due to the 
       free-bound (radiative recombination) continuum.

 EXPLANATION

       This routine does not use the same method of calculating the ion 
       continuum emissivities as the FREEBOUND routine. This is because a 
       modified version of FREEBOUND would be very slow for this purpose. 
       Instead, we use the method of Mewe et al. (A&AS 65, 511, 1986) which 
       is outlined in their Sect.2.2. The integration over the quantity 
       P_c(lambda,T) is very simple as the gaunt factor, G_c, has no 
       intrinsic lambda dependence other than through the limits.

       Comparisons between the wavelength-resolved continuum emission 
       derived from the Mewe et al. method with the more sophisticated 
       method employed in FREEBOUND show excellent agreement with at most 
       10% differences at specific wavelengths.

 CALLING SEQUENCE:

      fb_rad_loss, temp, int, min_abund=min_abund, /no_setup

 OUTPUTS

	TEMP    Temperatures (K). These are the temperatures at which the 
               ion fractions are defined (typically 10^4 to 10^8 in 0.1 
               dex intervals).

       INT     The emissivity in units of erg cm^3 s^-1.


 OPTIONAL INPUTS:

       MIN_ABUND Exclude elements whose abundances are less than MIN_ABUND. 
                 (Note that Ab(H)=1.)
	
 KEYWORD PARAMETERS:

	NO_SETUP   If the procedure setup_elements has already been called 
                  then the keyword /nosetup should be set to avoid 
                  repeating this step

 PROGRAMMING NOTES

       This routine computes the free-bound gaunt factor following the 
       prescription set out in Sect.2.2 of Mewe et al. (1986). The 
       expression for f_2 (Eq. 16 of Mewe et al.) contains several 
       quantities that need to be computed. Zeta_0 is computed internally 
       by the function ZETA_0 through a prescription evident from browsing 
       Table I of Mewe et al. Z_0 is computed from the ionization potential 
       of the recombined ion which is contained in the .ip file within the 
       database. The quantity n_0 (also used in deriving Z_0) is derived 
       using the routine CONF2N which extracts the highest n value from 
       the configuration description of the ground term of each ion.

       The quantity Z is just the charge on the recombined ion; E_0 is the 
       ionization potential of the recombined ion, while E_n_0+1 is derived 
       from Mewe's Eq.7 with the prescription that z_n=Z and n=n_0+1.

       The ions that are considered for the continuum are those for which 
       .fblvl files exist.

 COMMON BLOCKS:

	common elements,abund,abund_ref,ioneq,ioneq_t,ioneq_ref

 INTERNAL FUNCTIONS

       ZETA_0

 CALLS

       READ_IP,  ZION2FILENAME, SETUP_ELEMENTS, FILE_EXIST,
       READ_FBLVL, CONCAT_DIR, GET_IEQ

 EXAMPLES

       IDL> fb_rad_loss,temp,int
       IDL> plot,temp,int,/xlog,/ylog

 MODIFICATION HISTORY:

     Ver.1, 1-Aug-2002, Peter Young
          Completely new version of fb_rad_loss. Incorporates code from 
          a version of freebound not available in CHIANTI.

       V 2, 25-May-2005, GDZ 
                  corrected routine header.

 VERSION:   2, 25-May-2005