Core-electron spectroscopy of adsorbate ions: Iodine on Ag(111)

Abstract

Submonolayer coverages of iodine deposited on clean Ag(111) have been studied by x-ray photoelectron spectroscopy. The adsorbate core-electron binding energy is found to be 0.1-eV smaller at saturation than in the dilute limit, indicating that the iodine carries only a small negative charge. The low-energy electron diffraction evidence for clustering of the adatoms into the $\sqrt{3}\times \sqrt{3}$ structure at coverages considerably less than $\frac{1}{3}$ monolayer is confirmed by the observation, at those coverages, of a constant $14d$ binding energy. The excitation of silver surface plasmons by the core ionization of the adsorbate has also been observed.