Theory of the optical determination of surface anisotropy in molecular fluids

Abstract

It has recently been proposed that the liquid-vapour interface of simple molecular fluids, isotropic in their bulk phases, should exhibit an oscillatory anisotropy structure. It is proposed that this structure be investigated using surface optical reflection techniques. The ratio R/R₀ , where R is the reflectivity and R ₀ is the reflectivity of a hypothetical sharp liquid-vapour interface, will depend, inter alia, on the angle of incidence. Surface anisotropy is indicated if this dependence is itself polarization dependent. The effects are subtle, but are maximised if measurements are made in fluids of highly anisotropic molecules at about 95 per cent of the critical temperature.