Evidence for incomplete charge transfer and la-derived states in the valence bands of endohedrally doped La@C-82

Photoelectron spectra from sublimed layers of chromatographically separated La@C-82 are presented. Using photon energies corresponding to the La 3d to 4f transition, a resonant enhancement of the La-derived valence states is observed. From the calculated resonant intensities of La 5d and 5p states in a La atom we estimate that about 1/3 of an electron charge is left in the La-valence orbitals for La@C-82. In contrast to previous interpretations of La core-level photoemission studies our results demonstrate that the La valence electrons are not completely delocalized on the fullerene cage.