Photoionization of C₆₀ at High Energies

Calculations of the photoionization cross sections of C₆₀ including all valence and core subshells have been carried out for photon energies up to 1 keV using density functional theory (DFT) and time-dependent DFT (TDDFT) within the framework of a fully molecular model [1].  The high-energy valence subshell cross sections behave rather differently than the results from model potentials where the cross section falls far too rapidly with energy.  This unphysical behavior is traced to smearing out of the carbon nuclei in the model potentials which makes it difficult for momentum to be conserved at the higher energies.  In addition, it is found that confinement resonances persist with greater amplitude than in model calculations owing to the difference in much stronger reflection of the photoelectron wave off carbon nuclei as compared to reflection from the walls of  a potential well.  It was also found that interchannel coupling between valence and core cross sections is quite small except right near the inner-shell thresholds in the 300 eV region.  [1] A. Ponzi, S. T. Manson and P. Decleva, J. Phys. Chem. A 124, 108 (2020).