COLLISION INDUCED SCATTERINGSPECTRAL VIRIAL EXPANSION FOR COLLISION-INDUCED LIGHT SCATTERING IN GASES

Abstract

A general formalism is developed for the density dependence of depolarized light scattered by translational fluctuations in gases. In addition, absolute intensity measurements have been made of the depolarized light scattering spectrum of argon gas in the density range 20-150 amagats for the frequency range ω = 7-150 cm-1. At any given frequency, the intensity I(ω) can be expanded as a power series in the density I(ω) = I2(ω) p2 + I3(ω) p3 + ... The term I2(ω) is the light scattering spectrum caused by the optical anisotropy induced in a pair of atoms on collision, while I3(ω) represents the portion of the induced anisotropy in a three-body collision which cannot be represented as a sum of two-body effects. This is analogous to the familiar pV virial expansion. Spectra for the two- and three-body terms are reported and compared with predictions based on various models for the induced polarizability anisotropy