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

We investigate the influence of correlations among the valence-band el ectrons as well as correlations between valence-band and core electron s on the Auger line shape of solids. For metals with partially filled valence bands the relevant many-body problem is no longer exactly solv able. Usually, approximate solutions are constructed that correctly re produce different exactly solvable limiting cases. We employ a diagram matic vertex-correction method (three-particle ladder approximation) t o calculate the three-particle Green function, which directly yields t he Auger intensity. The validity of the approximation in limiting case s is discussed. It turns out that the three-particle ladder approximat ion 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 ap proximation to be a very reasonable interpolation between the differen t limits.