Light scattering studies of the dynamics and structure of liquids

Abstract

The polarizability density of a liquid may be expressed in terms of an intrinsic molecular polarizability and a contribution arising from intermolecular interactions. These terms give rise to components of the light scattering spectrum with shapes determined by molecular reorientational motions and by vibrational relaxation, for the intrinsic polarizability, and by motions which alter the relative separation and orientation of molecules, for the interaction-induced term. It is argued that these contributions to the spectrum are separable, provided that the correlation functions of the intrinsic and interaction-induced polarizabilities decay on well separated timescales. The intensities of the separated spectral components give information on the liquid structure. The lineshapes enable the rates of specific single molecule and intermolecular motions to be studied. The shapes and intensities of the interaction-induced and reorientational Rayleigh and Raman spectra of CS 2 and the vibrational relaxation of I 2 and CC1 4 solutions are discussed as examples.