Theory of Line Shapes

Abstract

The theory of absorption line shapes is reviewed as a special case of the kinetic theory of gases. Correspondence with low-frequency transport results in corrections to the impact theory and the statistical theory of line-broadening. These corrections are observed to be related to the general question of non-Markovian effects in kinetic theory. The various classifications of line-broadening are described in terms of the most important driving mechanisms of the absorbing atom distribution function and the damping mechanisms due to collisions. High-frequency transport on the other hand suggests a modification of the correlation function approach closely related to the results of elementary scattering theory. The wing spectrum of a line may thus be analyzed in terms of the relevant microscopic collisional rates.