Identification of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>s</mml:mi></mml:math>-derived Valence-Electron Level in Photoemission from Alkali-Metal Adlayers on Aluminum

Abstract

Photoemission spectra from potassium adsorbed on an Al{111} surface show a K $4s$-derived state just below the Fermi level, ${E}_{F}$, which is first observed just prior to the onset of ordering in the overlayer. The feature disperses upwards with increasing ${\mathbf{k}}_{\ensuremath{\parallel}}$ and crosses ${E}_{F}$ before reaching the Brillouin-zone boundary. Its coverage dependence is indicative of a transition from strongly ionic to metallic bonding.