Distribution of atoms at the surface of liquid mercury

Abstract

Theoretical studies of the anisotropic distribution of atoms in the liquid/vapour interface have led to two conclusions. First, the density along the normal to the interface (the longitudinal one particle distribution function) has different forms in a liquid dielectric and a liquid metal. In a dielectric1, the density decreases monotonically as one passes from the liquid to the vapour, while in a metal2 the liquid/vapour interface is stratified for about three atomic diameters into the bulk liquid, Fig. 1 shows examples. Second, the transverse structure factor at the surface of a liquid (the Fourier transform of the in-plane distribution of pairs of atoms) is very similar to the bulk liquid structure factor except near the origin, the difference arising from long-range correlations in the surface1. The very few experiments3,4 that can be interpreted in terms of the properties of the density along the normal to the liquid surface are in agreement with the first set of predictions. There have been no published reports on the transverse structure factor in the liquid/vapour interface. Here we describe the transverse structure factor of the room temperature liquid/vapour interface of mercury, determined using the method of grazing incidence X-ray diffraction5. Our experimental results are consistent with the above predictions.