Theory of Orientational Effects and Related Phenomena in Dielectric Liquids

Abstract

Formulas are developed for the molar constants of five nonlinear effects of molecular orientation in liquids; namely, the dielectric saturation in electric, magnetic, or optical fields and the electric as well as the magnetic birefringence. No assumption is made concerning the nature of the intermolecular forces, and no special model of molecular interaction is introduced. If the molecules may be considered to possess axial symmetry, four correlation factors RP, RCM, RK, and RS can be derived. These factors appear in the formulas of the molar constants of the Cotton-Mouton and Kerr effects, and of the effect of dielectric saturation in an electric, magnetic, or optical field. The correlation factors have been calculated as functions of θ(pq), the angle between the axes of symmetry of the pth and qth molecules, in the absence of a biasing field. The theory makes it possible to predict the value of the magnetodielectric saturation effect in diamagnetic liquids, as well as the photodielectric saturation, relating these phenomena to magnetic or electric birefringence. Moreover, the meaning of this theory consists in the fact that it gives a quantitative explanation of the inverse saturation effect appearing in some polar liquids and increasing their dielectric constant. Satisfactory results have been obtained by applying this theory to such phenomena as light scattering in liquids or the lowering of the freezing point, in which the orientationally dependent intermolecular forces play an important part.