The Frequency Dependence of the Dielectric Properties of Dipolar Substances

Abstract

A critical review of theories of the frequency dependence of the dielectric constant of dipolar substances is given and inconsistencies are pointed out in previous attempts to account for dipolar interaction. A new theory is presented based on Debye's theory of molecular relaxation and using Onsager's method for treating electrostatic inter- action. Fluctuations are considered explicitly both in the orientation of an individual dipole and in the local field acting on it ; a distinction is also made between the experimentally measurable time constants and the relaxation times governing molecular processes. The results are presented m the form of a series development in pourers of the dipolar concentration. In first approximation the theory leads to a Debye frequency dependence of the dielectric constant ; in second approximation a Debye dependence can be made consistent with the molecular mechanism only for a more restricted (two-position) model.