X-ray reflectivity study of the surface of liquid gallium

Abstract

X-ray reflectivity from the surface of liquid gallium was measured under ultrahigh vacuum conditions using a novel technique for curved surfaces. The small deviations between the measured and theoretical Fresnel reflectivity for an ideally sharp flat interface for wave-vector transfer \ensuremath{\lesssim}0.5 A${\mathrm{\r{}}}^{\mathrm{\ensuremath{-}}1}$ imply an interfacial width for the electron density profile of \ensuremath{\lesssim}1.3\ifmmode\pm\else\textpm\fi{}0.2 A\r{}. This is consistent with a model of atomic close packing which lacks structure along the surface normal at length scales >10 A\r{}.