Add file reader for rrlvl files

[jwreep]

Fixes #114

Tested with data from CHIANTI v10.

(base) C:\Users\reep\Documents\Forks\fiasco>python
Python 3.11.5 | packaged by conda-forge | (main, Aug 27 2023, 03:23:48) [MSC v.1936 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> from astropy.table import QTable
>>> import fiasco.io
>>> parser = fiasco.io.Parser('fe_23.rrlvl')
>>> table = parser.parse()
>>> table
<QTable length=459>
lower_level upper_level      temperature        recombination_rate
                                  K                  cm3 / s
   int32       int32         float64[19]           float64[19]
----------- ----------- ---------------------- --------------------
          1           1 5290.0 .. 5290000000.0 9.54e-12 .. 6.54e-16
          1           2 5290.0 .. 5290000000.0 4.93e-12 .. 4.18e-17
          1           3 5290.0 .. 5290000000.0 1.47e-11 .. 1.25e-16
          1           4 5290.0 .. 5290000000.0 2.41e-11 .. 2.07e-16
          1           5 5290.0 .. 5290000000.0 1.37e-11 .. 1.22e-16
          1           6 5290.0 .. 5290000000.0  4.2e-14 .. 3.39e-18
          1           7 5290.0 .. 5290000000.0 2.77e-13 .. 2.43e-17
          1           8 5290.0 .. 5290000000.0 4.69e-12 .. 2.97e-16
          1           9 5290.0 .. 5290000000.0 1.51e-12 .. 9.87e-17
        ...         ...                    ...                  ...
          3         153 5290.0 .. 5290000000.0 1.05e-12 .. 8.85e-19
          3         155 5290.0 .. 5290000000.0 3.78e-13 .. 1.59e-19
          3         165 5290.0 .. 5290000000.0 5.29e-13 .. 2.23e-19
          3         158 5290.0 .. 5290000000.0  6.8e-13 .. 2.87e-19
          3         160 5290.0 .. 5290000000.0  8.32e-13 .. 3.5e-19
          3         162 5290.0 .. 5290000000.0 5.29e-13 .. 2.23e-19
          3         159 5290.0 .. 5290000000.0  6.8e-13 .. 2.87e-19
          3         161 5290.0 .. 5290000000.0  8.32e-13 .. 3.5e-19
          3         163 5290.0 .. 5290000000.0 9.83e-13 .. 4.14e-19
          3         166 5290.0 .. 5290000000.0  1.87e-13 .. 4.5e-20
>>> table.meta
OrderedDict([('footer', "filename:  fe_23.rrlvl\nRadiative recombination rates for recombination onto Fe XXIV to form Fe XXIII\nBadnell, N. R., 2006, ApJS, 167, 334\nRadiative Recombination Data for Modeling Dynamic Finite-Density Plasmas\nadsLink:  http://adsabs.harvard.edu/abs/2006ApJS..167..334B\nproduced as a part of the 'CHIANTI' atomic database for astrophysical spectroscopy\nK. Dere (GMU) - 2018 December 15\nChanged indexing for v.10.\nProduced as part of the 'CHIANTI' atomic data base collaboration by\nGiulio Del Zanna, May 2020"), ('chianti_version', '8.0.7'), ('filename', 'fe_23.rrlvl'), ('descriptions', {'lower_level': 'lower level index', 'upper_level': 'upper level index', 'temperature': 'temperature', 'recombination_rate': 'recombination rate coefficient'}), ('element', 'fe'), ('ion', 'fe_23'), ('dielectronic', False)])
>>>

[wtbarnes]

Ha we are working the same thing at the exact same time but you beat me to it!

[jwreep]

Sorry for the overlap! Seemed like it would be simple enough to implement. The file format is basically the same as a few other types except that the temperatures are not in log-space.

[wtbarnes]

No worries! Your solution was actually a bit more straightforward than mine. I'm actually pleasantly surprised that someone who is not me is able to read the parsing code and work out how to write a new file parser.

I'm going to add one more commit here and then I'll go ahead and merge. Thanks for tackling this.

[jwreep]

Might need one quick update for the description:

These files contain the *Direct* radiative recombination rates from
    the recombining ion to the recombined ion. Note that these files contain
    the *effective* radiation recombination rate coefficients.

The .reclvl contain effective radiative recombination rates, not the .rrlvl files.

[wtbarnes]

Ah good point. I'll create an issue.