1sx-ray-absorption spectroscopy ofC60: The effects of screening and core-hole relaxation

The C 1s near-edge absorption spectrum of ${\mathrm{C}}_{60}$ has been studied experimentally and theoretically. An assignment of the C 1s transitions to unoccupied states below the continuum threshold is suggested on the basis of multiple-scattering Xα local density and semiempirical intermediate-neglect-of-differential-overlap self-consistent-field calculations, including effects of screening and relaxation of the symmetry-breaking core hole. The present work shows that modeling the core hole is necessary for understanding the absorption spectrum of ${\mathrm{C}}_{60}$. Thus excitonic interactions between the excited electron and the core hole left behind give a final state that is significantly different from the ground state.