Charge transfer between the Au(111) surface and adsorbed C-60: Resonant photoemission and new core-hole decay channels

The interaction of C60 with the Au(111) surface has been investigated using synchrotron radiation-based electron spectroscopy. Resonant photoelectron spectroscopy and autoionization spectroscopy have been used to probe the coupling between the molecule and the substrate. Three distinct high energy spectator Auger features were observed that are only evident for a monolayer of C60 chemisorbed to the Au(111) surface and not a multilayer or the clean surface itself. Combined with C 1s x-ray absorption and valence band spectra, the data suggest a decay process not previously reported for this system. This is a spectator decay channel involving electrons transferred from the gold substrate to the adsorbed molecule, either in the ground state or during the timescale of the core-hole lifetime. Both possibilities are considered in the interpretation of the results, which support, on balance, a ground state charge transfer.