Semiclassical theory of molecular spectral line shapes in gases

Abstract
A semiclassical theory of the width and shift of molecular spectral lines is developed for gases. Overlapping and nonoverlapping lines are considered, within the framework of the impact approximation. Use is made of ``exact'' semiclassical theory of molecular collisions, recently developed by Miller and by Marcus, and of developments in the quantum mechanical theory of spectral line shapes, by introducing the former into the latter. Comparison is made with a classical‐like approach.