Consideration of dielectric relaxation and the Kerr-effect relaxation in relation to the reorientational motions of molecules

Abstract

Relations between field-free orientational time-correlation functions and dielectric and Kerr-effect responses to step-on and step-off electric fields are considered. Whereas the dielectric and Kerr-effect decay transients are simply related to 〈P₁(u, t)〉 and 〈P₂(u, t)〉, where u= cos θ, the rise transients are not, in general, related to these quantities; assumptions and specific reorientation mechanisms are required in order to understand the rise transients. The dielectric and Kerr-effect relaxations are considered for the models of rotational diffusion and “fluctuation relaxation”. Experimental data for poly-n-butylisocyanate in solution and tritolyl phosphate are discussed in terms of the theory and mechanisms for motion.