Series
IAU G5 talk: Inelastic hydrogen collisions in stellar atmospheres

Abstract

Accurate non-LTE modelling of stellar spectra, and thus the derivation of accurate stellar properties such as chemical composition, temperature, and surface gravity, depends on reliable atomic data.  While inelastic electron collisions are very important even in FGK stars, the relative importance of the more abundant yet less efficient hydrogen collisions has for a long time been a major source of uncertainty.  Over the last decades, considerable progress has been made on the theoretical side, as well as with experiments for the important charge transfer processes involving hydrogen, both covering a significant number of astrophysically important atoms.  I will review this progress, and discuss where further progress might be needed.