Potassium-induced empty electronic states on Ag(110)

The unoccupied level structure of K and Na adsorbed on a Ag(110) surface has been probed by inverse photoemission. A peak is observed initially \ensuremath{\sim}3 eV above ${E}_{F}$, which shifts in energy towards the Fermi level as a function of increasing coverage. The dispersion of this feature is consistent with a ${p}_{z}$ character of the observed empty state. For CTHETA>0.3 new structures appear in the spectra indicating the formation of a metallic layer. Energy position, coverage dependence, and dispersion of the unoccupied level are in striking agreement with predictions made on the footing of previous ultraviolet photoemission spectroscopy, electron energy-loss spectroscopy, and theoretical results.