INFLUENCE OF ELECTRON CORRELATIONS ON AUGER-SPECTRA OF SOLIDS WITH PARTIALLY FILLED BANDS

We investigate the influence of correlations among the valence-band electrons as well as correlations between valence-band and core electrons on the Auger line shape of solids. For metals with partially filled valence bands the relevant many-body problem is no longer exactly solvable. Usually, approximate solutions are constructed that correctly reproduce different exactly solvable limiting cases. We employ a diagrammatic vertex-correction method (three-particle ladder approximation) to calculate the three-particle Green function, which directly yields the Auger intensity. The validity of the approximation in limiting cases is discussed. It turns out that the three-particle ladder approximation gives correct results not only for those cases considered commonly but also for another limiting case: the limit of strong valence-band-core interaction. Numerical results for a model system indicate the approximation to be a very reasonable interpolation between the different limits.