Dielectric Relaxation of Molecules Containing Rotating Polar Groups

Abstract

Debye's theory of dielectric relaxation has been extended to molecules consisting of two similar polar groups, which cannot rotate freely relatively to one another owing to their mutual potential energy. As a result, the mean dipole moment of the molecule in the field F₀ exp(iωt) can be expressed by a sum of terms of Debye's type, namely C_λ/(1+iωτλ), where the relaxation times τλ and the constants C_λ are determined by an eigenvalue problem. τλ and C_λ are calculated in the case of the cosine coupling between the groups and in the case of the quasi‐elastic bond. The results are compared with the experimental data for chloro‐derivatives of diphenyl.