Theory of the Auger effect in solids: Plasmon effects in electron spectroscopies of valence states

Abstract

A theory of XPS and AES spectra of valence states of atoms in solids is proposed that allows for holeplasmon interactions in the final state. The model Hamiltonian includes an interaction term between plasmon field and the resonant valence atomic orbital. The exact solution of the model is found for any shape of the unperturbed local density of states. Plasmon effects show up not only as plasmon satellites, but also as a very significant change in the shape of the main peak. The coupling to the boson field tends to localize the valence hole. Eventually, if the coupling is strong enough compared to the level width, sharp resonances appear in the spectra due to localized, small-polaron-like states. The degree of validity of a Born-Oppenheimer approximation is assessed by comparison with the present exact results.