SPECTRA
=======

ExoCross can be used with the SPECTRA line list format developed by iao.ru  by adding the `SPECTRA` keyword anywhere in the input file (outside any section). 
This will also require the definition of the (i) reference temperature, (ii)  partition function for the target temperature, (iii)
partition function for the reference temperature, and (iv) the molecule/isotope pair  (`iso`). 

SPECTRA broadening parameters (as part of the format) will be used unless the species-section is given, which specifies the broadening.  
The .states file is not required and ignored if given. The SPECTRA reference intensity is used directly to compute the intensity for the target temperature.

For example: 
::

    Temperature  500.0  ref 296.0
    Range 0.0  10000.0
    
    Npoints 10001
    
    absorption
    Voigt
    
    spectra
    iso 26 1
    pf 1000.0 ref 500
    
    output CH4_voigt_T500K

    Transitions  SpectraMol_CH4_296K.txt
    

Units
=====
   

The standard intensity  untis of line intensities are cm/molecule (absorption) and erg s /molecule/str (emission). The intensity units of cross sections are
intenity units times cm. The emission units can be changed to watt/molecule/str or to photons/s by adding the corresponding units tot the `emission` keyword, e.g.

    
    emission photons/s
    
or 

    
    emission watt
    
    
ExoCross uses  wavenumber as to represent the spectral range. The units are cm:math:`^{-1}`. 


The temperature is measured in K. 


The units of the cooling funciton is the same as the units of the emission spectrum (erg s/ str / molecule).