Spectral lines Definition and 52 Threads

can anyone give me some good sites for spectral lines and understand how and why spectra occur. Possibly only using the bohr atom. I am a chemistry teacher in maryland, and I'm trying to find some good places so my students could do a search or look at some things online. any ideas...

I'm trying to understand this application of thermodynamics to astronomical inferrence. As I understand it, the temperature of a diffuse gas cloud in distant space can be inferred from the relative intensities of the spectral lines (correct?) which indicates the distribution of the population...