Influence of many-electron effects in the C60 carbon K-shell absorption spectrum.

Abstract

In the first part of this work we develop a model describing the influence of many-electron effects in ${\mathrm{C}}_{60}$ K-shell photoemission (only the \ensuremath{\pi} valence electrons are taken into account). Then we extend this model to the calculation of the ${\mathrm{C}}_{60}$ K-shell absorption spectrum. We first determine a one-electron spectrum obtained by considering only direct transitions from the 1s to the unoccupied valence levels. This spectrum exhibits three main peaks. Then, following a previous Friedel's analysis, we add two kinds of many-electron effects. In the first step, we include the transitions with shake-off excitations. The obtained spectrum is similar to the one-electron spectrum for the positions and the relative intensities of the three peaks, however, a high-energy tail appears. In a second step we also include replacement transitions. Then the relative intensities of the three peaks vary and are in better agreement with experiment than in the one-electron spectrum. The differences with experiment which still remain are discussed.