Theory of spectral line shape. III. The Fano operator from near to far wing

Abstract

In this third part of a theory of spectral line shape, applicable to conditions of atmospheric transmission, an evaluation of the frequency dependence of the complete Fano collision operator has been made using the collision time theory developed earlier. This results in a considerable reduction of the terms in the Fano operator. An analysis of the spectral line wing shows that there are two different regimes: the near wing and the far wing. These regimes are demarcated by a turning point at a frequency displacement of kT/h. In the very far wing, beyond the turning point, the behavior of the Fano operator changes and the effects of binary collision overlap and photon absorption into the binary collision complex become important. The line wing behavior is corroborated qualitatively by experimental results for carbon dioxide near 4.2 μm.