Many-body effects in x-ray photoemission from magnesium

Abstract

X-ray photoemission experiments were performed on samples of magnesium and aluminum prepared with clean surfaces in ultrahigh vacuum. Core-level binding energies were in excellent agreement with x-ray emission data. Asymmetries in core-level peaks were observed and are compared with theory. The Mg $\mathrm{KLL}$ Auger spectrum showed kinetic energies higher than the literature values. Many-body effects, in the form of extra-atomic relaxation, were present in core levels and Auger lines. Both $K{L}_{1}V$ and $K{L}_{2,3}V$ Auger peaks of Mg were observed. Many-body effects were also manifest as rich plasmon satellite structure accompanying every primary peak. The valence-band spectrum was compared with x-ray emission data and with the $K{L}_{2,3}V$ peak. The spectra were interpreted in terms of energy-level diagrams rather than one-electron "levels." It is argued that valence-band spectra obtained by different methods can be compared most directly among states with the same number of core holes. A hierarchical classification of hole states is suggested. The effect of the degree of localization of the hole state on the relaxation energies in metals is discussed and shown to be small. Finally it was observed that in several light metals the energies required to remove a valence-band electron or a unipositive ion core are about equal.