Theory of k-Independent Depolarized Rayleigh Wing Scattering in Liquids Composed of Anisotropic Molecules

Abstract

A discussion is presented of the k-independent factors that contribute to the depolarized Rayleigh wing scattering in liquids composed of anisotropic molecules. The spectrum consists of a sharp line (several tenths cm−1) and a broad line (several cm−1 or tens of cm−1). It is suggested that the spectrum arises from at least two separate processes, each of which induces fluctuations in off diagonal elements of the dielectric tensor: molecular reorientation, which is a relatively slow process, and some form of intermolecular interaction, which is a rapid process. The autocorrelation functions for the slow and rapid processes account in large part for the sharp and broad lines, respectively; however, the heretofore neglected cross correlation function between the slow and rapid processes may contribute significantly to the spectrum, particularly to the sharp line which may be appreciably reduced in intensity due to the cross correlation. This reduction in sharp line intensity suggests that the difference between the observed integrated sharp line intensity and that expected on the basis of single particle static orientational correlations, 〈D(1)D(1)〉, cannot be simply related to the presence of two particle static orientational correlations, 〈D(1)D(2)〉.