Abstract:
Ultraviolet photoelectron spectra (UPS) of Y@C82 have been measured with a synchrotron light source.
UPS spectra reveal the photoelectron onset at 0.3 eV below the Fermi level, indicating the semiconducting
nature of the metallofullerene, and contain low-binding-energy features associated with charge transfer from
the encapsulated atom to molecular orbitals. As for empty fullerenes, when the incident photon energy is
varied, the relative intensities of the valence-band features of Y@C82 oscillate, showing that the endohedral atom does not significantly disturb the photoelectron interference effects of the fullerene cage. For
K2.3Y@C82, which forms a fcc-like structure, core and valence states of Y@C82 broaden and shift to higher binding energies but there is no evidence of density of states at the Fermi level. Finally, although core and
valence states of Y@C82 change considerably upon an intercalation of potassium, the encapsulated atom is
well shielded from the outside chemical environment and its valency remains close to 3+.
