Azimuthal Anisotropy in Deep Core-Level X-Ray Photoemission from an Adsorbed Atom: Oxygen on Copper(001)

Abstract

For oxygen adsorbed on a Cu(001) surface, the O $1s$ x-ray photoelectron intensity is found to exhibit a complex azimuthal anisotropy with an overall amplitude of \ensuremath{\sim} 26% for a grazing 10\ifmmode^\circ\else\textdegree\fi{} angle of emission. No significant anisotropy is observed at 45\ifmmode^\circ\else\textdegree\fi{}. Several reasons for expecting a direct relationship between such final-state scattering effects and atomic geometry are discussed, and the data are found to be suggestive of a surface-chemisorbed $c(2\ifmmode\times\else\texttimes\fi{}2)$ oxygen overlayer in fourfold coordination.