Forced diffusion of molecules with internal rotation

Abstract

The dipolar correlation function for a system of independently relaxing molecules containing rotatable groups is calculated by solving the forced diffusion equation. It is found that the correlation function has the same form as a previous result for spheroids. This result follows from the assumption that the equilibrium distribution function is constant, an assumption made to allow linearization of the diffusion equation. Procedures for relieving the assumption are outlined and applied to a hindered internal rotation case. The presence of a barrier to internal rotation makes the correlation function decay more slowly. The relation between the multimolecular correlation function and the complex dielectric permittivity is investigated.