Rb-intercalated C60 compounds studied by photoemission spectroscopies

We report on a combined photoemission and inverse photoemission spectroscopy analysis on RbxC60 compounds with different stoichiometries (0 <= x <= 6). Apart from shifts and broadening of the spectral features associated to the different phase formed, we observe in the RbC60 phase the presence of the highest occupied molecular orbital (HOMO) shoulder and of its symmetric (with respect to the Fermi level) empty state. According to calculations, the metallicity of this phase and the presence of these electronic states may be taken as a fingerprint of the interplay between electron-electron and electron-phonon interactions in determining the electronic behavior of alkali metal fullerides. (c) 2005 Elsevier B.V. All rights reserved.