A STOCHASTIC CAGE MODEL FOR LINEAR SOLUTES

A stochastic cage model describing a linear solute reorienting under t he action of a librational potential due to neighboring solvent molecu les is presented. The fluctuations of the cage structure are taken int o account by means of a suitable distribution of the Librational frequ ency, Moreover, a detailed description of the cage dynamics is introdu ced by considering both the cage rotation and its restructuring throug h randomizations of the Librational frequency and of the equilibrium o rientation of the solute. With a suitable choice of the basis function s for the representation of the time evolution operator, the cage mode l can be solved numerically in order to compute different types of dyn amical observables: angular momentum and orientational correlation fun ctions, frequency dependent dielectric permittivity, and far-infrared spectra. Typical behavior of such observables in normal liquids is rec overed from the cage model, thus demonstrating its capability of descr ibing experimental observations at quite different time scales. (C) 19 97 American Institute of Physics.