Molecular relaxation times from time-variations of dispersion and absorption of third-order electric polarisation in liquids

Abstract

Processes involving an increase in nonlinear 3rd order electric polarisation in dipolar liquids by the action of external electric fields are considered in the approximation of Debye's rotational diffusion model of geometrically spherical molecules. For times comparable with the Debye times of molecular orientation, we show that the dispersion and absorption of the above effects are described by the well known Debye factors R_l(ω) and supplementary factors R_lk(ω), and that the setting in of steady state polarisation depends on the relaxation times τ₁, τ₂. We perform a detailed analysis of the case of quadratic changes in electric permittivity in a static electric field.