Surface relaxation energies in core level spectroscopies of adsorbed atoms and molecules

Abstract

Core level holes which are created in electron emission spectroscopies of atoms and molecules adsorbed or condensed onto metal surfaces induce a screening charge at the surface. The Coulomb interaction between the induced and the hole charge, called the extra-atomic relaxation energy, shifts the apparent binding energy of the ejected electron from the value inferred from an orbital energy. In this paper, linear response screening shifts are calculated for a number of different response functions which also allow for the polarizability of the adsorbed layers. The relation between classical image potential shifts and those obtained here is quantitatively compared. As an example, the X-ray photoelectron spectrum of SF 6 physisorbed on Ru surfaces is interpreted in terms of the present theory.