INFLUENCE OF MANY-ELECTRON EFFECTS IN THE C60 CARBON K-SHELL ABSORPTION-SPECTRUM

In the first part of this work we develop a model describing the influ ence of many-electron effects in C60 K-shell photoemission (only the p i valence electrons are taken into account). Then we extend this model to the calculation of the C60 K-shell absorption spectrum. We first d etermine a one-electron spectrum obtained by considering only direct t ransitions from the 1s to the unoccupied valence levels. This spectrum exhibits three main peaks. Then, following a previous Friedel's analy sis, we add two kinds of many-electron effects. In the first step, we include the transitions with shake-off excitations. The obtained spect rum is similar to the one-electron spectrum for the positions and the relative intensities of the three peaks, however, a high-energy tail a ppears. In a second step we also include replacement transitions. Then the relative intensities of the three peaks vary and are in better ag reement with experiment than in the one-electron spectrum. The differe nces with experiment which still remain are discussed.