Evidence for Incomplete Charge Transfer and La-Derived States in the Valence Bands of Endohedrally DopedLa@C82

Photoelectron spectra from sublimed layers of chromatographically separated $\mathrm{La}@{\mathrm{C}}_{82}$ 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 $\frac{1}{3}$ of an electron charge is left in the La-valence orbitals for $\mathrm{La}@{\mathrm{C}}_{82}$. 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.