Light Scattering by Coupling of Orientational Motion to Sound Waves in Liquids

Abstract

The fine features in the Rayleigh wings of light scattered from various liquids, observed by Starunov, Tiganov, and Fabelinskii, and by Stegeman and Stoicheff, and associated with shear waves according to the Leontovich theory, are explained from a molecular correlation-function point of view, based on the Kubo–Zwanzig–Mori theory. These features are attributed to a “bottleneck” effect, in which the short-lived Brownian orientational motion (“tumbling”) is coupled to a long-lived (hydrodynamic) sound mode. Line-shape expressions and an estimate of the magnitude of the effect are given.