KINETIC-THEORY OF BAND SHAPES IN MOLECULAR-SPECTRA OF GASES - APPLICATION TO BAND WINGS

A kinetic theory of spectral band shapes is developed which accounts f or the effects of line mixing and finite duration of collisions. The t heory is based on a projection operator technique with a nonorthogonal metric. The roles and hierarchy of various approximations commonly em ployed are analyzed. It is shown that the relaxation operator must be defined before the initial correlations are suppressed so that the dou ble sum rule for the matrix elements of this operator is conserved. Th is conservation is important for the calculations of the wings of band shapes. Rotovibrational band shapes for some specific cases of Raman and infrared absorption spectra of gases are considered. The expressio ns obtained relate the band wing profiles with the spectral density of molecular torque arising from binary collisions. (C) 1998 American In stitute of Physics.