Anisotropy of the dielectric function within a liquid-vapour interface

Abstract

We calculate e⊥(z) and e∥(z), the dielectric functions which characterize the response of a planar interface to an electric field perpendicular to or parallel to the interface. These functions each differ from the Clausius-Mossotti form by an interface term, which depends on the variation in density and in the pair correlation function through the interface. Detailed calculations are carried out for Ar, Kr and Xe, using a molecular dynamics pair correlation function, and three model density profiles. The effect of anisotropy on ellipsometric estimates of the interface thickness is found to be small, because of cancellations between opposing terms.