Photoemission Spectroscopy in the Presence of Adsorbate-Covered Surfaces

A theory of the ultraviolet photoemission spectroscopy of metals with adsorbate covered surfaces yields ${Δ}j({ω}){∝}{{G}ₐₐ}I({ω}{-}{{ω}}₀){-}D{{G}ₐₐ}R({ω}{-}{{ω}}₀)$. ${Δ}j({ω})$ is the excess current at the energy ${ω}$ produced by the adsorbates, ${{ω}}₀$ is the photon energy, $({1}{{π}}){{G}ₐₐ}I$ is the density of states at the adsorbate, and ${{G}ₐₐ}R$ is the real part of the Green's function at the adsorbate. $D$ is nonzero if ${ω}{-}{{ω}}₀$ is degenerate with the metal energy bands, and can be large ($D{~}1$) for typical experimental conditions.