ONE, 2 AND 3-BODY FEATURES IN AUGER CVV SPECTRA

We develop a simple variational approximation for the ground state of a conduction band in the presence of a localized core-hole potential, which fulfils the Anderson orthogonality theorem. Using this as the in itial state of the Auger decay, we derive an expression for the line s hape, including correlation effects in the Ladder Approximation. The c omputed spectrum is a combination of one-hole and two-hole-one-electro n contributions; it is similar to the experimental spectra of low -ele ctron-density systems that show the apparent negative U behaviour. The se results show that in such systems the conduction electrons effectiv ely screen the core hole before it decays. Also, we present evidence f or a transition from complete relaxation to no relaxation with increas ing band filling; the ''unrelaxed'' contribution to the spectra reflec ts a two-holes density of states.