The chemical composition of stellar atmospheres is usually obtained from absorption lines.
The analysis ingredients are a good spectrum, a model of the temperature and density structure of the stellar atmosphere and a catalogue of atomic and molecular transitions. It is these latter things that I think you seek.
Such "linelists" are found in many places; consisting of line wavelengths, excitation potentials and oscillator strengths.
One very useful compilation/database is the VALD atomic line database. Other catalogues exist for molecular transitions -e.g. Tennyson & Yurchenko 2012. However, these lists are usually just the starting point. Most spectroscopists tune their lists by a careful comparison with the spectrum of the Sun, or other standard stars.