Simulation: spectroscopy with fortran or anything else

[mosy_gh23]

hi friends,
I'm going to simulate the spectrum of a specific ion, with constant situation (like: density, temperature and etc).
but I don't know what should I do first!
thanks for your help

 

[mosy_gh23]

thanks for large amount of replys!
I really couldn't choose the best answer through them! all was great...