Dynamic Kerr-effect and dielectric relaxation of polarizable dipolar molecules. Transient response including linear and non-linear effects
The transient response functions for Kerr-effect relaxation and dielectric relaxation are investigated for the case of polarizable dipolar molecules subjected to “step-on” and “step-off” applied electric fields. Relations are derived between the experimental observables and the angular correlation functions for motion. Whilst the Kerr-effect rise and decay functions are equivalent for the induced dipole-moment contribution, the corresponding functions are not equivalent, in general, for the permanent dipole moment contribution. The Kerr-effect decay function may be expressed in terms of field-free angular correlation functions and, whilst it is possible to partially express the Kerr-effect rise function in terms of these correlation functions, one term in the expression remains as an unsolved problem. The relationship of the present theory to that given by Cole for axially symmetric molecules and to our previous experimental studies of Kerr-effect and dielectric relaxation in viscous liquids is briefly discussed.