  Using a helium ion hitting various metal surfaces as a model system, we
describe a general quantum-kinetic approach for calculating ion-induced
secondary electron emission spectra at impact energies where the emission is
driven by the internal potential energy of the ion. It is based on an effective
model of the Anderson-Newns-type for the subset of electronic states of the
ion-surface system most strongly affected by the collision. Central to our
approach is a pseudo-particle representation for the electronic configurations
of the projectile which enables us, by combining it with two additional
auxiliary bosons, to describe in a single Hamiltonian emission channels
involving electronic configurations with different internal potential energies.
It is thus possible to treat Auger neutralization of the ion on an equal
footing with Auger de-excitation of temporarily formed radicals and/or negative
ions. From the Dyson equations for the projectile propagators and an
approximate evaluation of the self-energies, rate equations are obtained for
the probabilities with which the projectile configurations occur and an
electron is emitted in the course of the collision. Encouraging numerical
results, especially for the helium-tungsten system, indicate the potential of
the approach.
