Core-Level Binding Energy and Density of States from the Surface Atoms of Gold

X-ray photoemission spectra of $4f$ and valence electrons in surface atoms of gold have been obtained. The surface-atom $4f$ level is shifted 0.40±{}0.01 eV to lower binding energy relative to the bulk value. The surface density of states is narrowed by (7.6 ±{} 1.1)% and its center of gravity is shifted to lower binding energy by 0.51±{}0.08 eV. A model is proposed to account for the core-level shift in terms of the modified surface density of states.