Surface Layering in Liquid Gallium: An X-Ray Reflectivity Study

Abstract

Surface-induced atomic layering in liquid gallium has been observed using x-ray reflectivity, ultrahigh vacuum conditions, and sputtered clean surfaces. Reflectivity data, collected on a supercooled liquid sample to momentum transfers as large as ${q}_{z}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}3.0{\AA{}}^{\ensuremath{-}1}$, exhibit a strong maximum near 2.4 \AA{} ${}^{\ensuremath{-}1}$ indicating a layer spacing that is comparable to its atomic dimensions. The amplitude of the electron density oscillations decays with a characteristic length of 6 \AA{}. This is unexpectedly twice that of recent results for Hg, and the difference may be related to covalent bonding or supercooling.