Electron structure of Na and K adsorbed on Ni (100)

Abstract

Electron excitations of Na and K adsorbed on Ni (100) have been investigated by means of electron energy loss spectroscopy. The experiments were performed in conjunction with measurements of adatom distributions and work function changes. Excitations from occupied valence and core states to unoccupied valence states and a collective excitation among the valence electrons are reported. It is found that the excitations are characterized by their dependence on the surface density and the charging state of the adatoms. The excitation among the valence states decreases in energy with increasing density due to the electrostatic interaction among the charged adatoms. This observation has in conjunction with the work function data been utilized to explore the adatom valence electron structure and charging. The observed shifts of the Na2p and K3p core level excitation thresholds are consistent with these charge assignments.