VALENCE AND CORE PHOTOELECTRON-SPECTROSCOPY OF C60, BUCKMINSTERFULLERENE

The MgK-alpha-X-ray (XPS) and He(I)/He(II) ultraviolet (UPS) photoelectron spectra of several thin films of C60 (one to three monolayers) prepared by vapor deposition on gold are reported. The core XPS spectrum shows a single narrow carbon 1s ionization at 285.1 eV. The valence UPS spectra show very sharp valence ionization bands, comparable to gas phase spectra, with wide separations between the lowest ionization energy features. The ionizations are consistent with theoretical calculations based on the highly symmetric truncated icosahedral structure. The first vertical ionization energy relative to the vacuum level is estimated to be 7.6+/-0.2 eV from these solid state measurements.