Cross terms and Kirkwood factors in dielectric relaxation of pure liquids

Abstract

Dielectric relaxation reflects fluctuations of the total electric dipole moment of a liquid sample. If summed over molecular dipole moments, one obtains cross terms between molecular dipole moments of different particles which reflect collective contributions to dielectric relaxation. In the static case these collective effects are characterized by the well-known Kirkwood correlation factor g K . By comparing the dielectric relaxation times τ d of pure liquids with the single particle relaxation times τ s estimated from nuclear magnetic relaxation data, we show that collective effects affect the dynamical dielectric behavior. There is evidence for a relation of the simple form τ d = g K τ s .