Calculation of the shakeup structure of the C60 1s photoemission spectrum

We make a theoretical study of the shakeup structure of the C60 1s photoemission spectrum. The method takes into account the reactions of all the π electrons which accompany the photoelectron emission. The calculation is a priori very long since there are 1034 possible final states to be considered. We show that the calculation can be restricted to the states which differ from the final ground state by creating electron-hole pairs in a set of 15 particular molecular wavefunctions. The comparison to experiment allows one to fix the parameters of the calculation. We find for the hopping integral: β ∝ -1.15 - 1.05 eV and for the local attractive term which appears in the final state: Δ = 2 β. Once these parameters are fixed, several features of the experimental spectrum are well explained by the model. We also calculate the shakeup structure of the 1s C60 X-ray emission spectrum. (orig.)