Fine structure of C60 photoionization cross-section oscillations

We have measured the angle-resolved photoemission spectroscopy of a C-60 single crystal in the low photon energy region from 13.0 to 34.0 eV with small increments (0.5 or 1.0 eV). The ratios of partial photoionization cross-sections for the HOMO and HOMO-1 bands exhibit many fine structures. The energy positions of the fine structures agree well with the giant resonances of dipole transition between individual molecular orbitals, which were predicted by a quantum chemistry model. The magnitudes of the HOMO/ HOMO-1 ratios, however, indicate further theoretical works are still needed. The important role of collective excitation in the photoionization cross-section of C-60 is suggested.