I'm looking for some reference listing spectral lines outside the visible spectrum. (In particular, I'm looking for an element or compound that emits strongly in the 700-900nm range.)
Assuming your question is a reference request:
I now about one resource that has a very broad range of spectral data, the
This has worked great for me.
Both potassium (766.5+769.9 nm) and sodium (818.3+819.4 nm) have strong resonance lines (doublets) in this part of the spectrum. There are also the calcium triplet lines at 849.8+854.2+866.2 nm.
These are the strongest atomic absorption lines seen in the spectra of solar-type stars or cooler at 700-900 nm.
A more specific answer would require the spectral type of the star.
To do something more general and/or extensive you would need to get hold of a good line list (a line list alone cannot easily tell you which lines will appear strongest in a stellar spectrum) and a spectral synthesis programme like SME or MOOG.