Azimuthal Anisotropy in Core-Level X-Ray Photoemission fromc(2×2)Oxygen on Cu(001): Experiment and Single-Scattering Theory

Azimuthal anisotropies in core-level x-ray photoemission from $c(2\mathrm{}\times 2)\mathrm{O}$ on Cu(001) have been found to show a strong dependence on polar emission angle. The anisotropies observed are $\frac{\Delta I}{I_{max}}\lesssim 24\%$ for O 1s emission, and ≲ 41% for Cu $2p_{\frac{3}{2}}$ and Cu $3p$ emission. A single-scattering theoretical model is found to describe well both the O and Cu data, and suggests that O is present in fourfold coordination sites for which the O atoms are coplanar with the Cu surface atoms.