EXCITATION-ENERGY AND TEMPERATURE-DEPENDENT RAMAN-STUDY OF RB3C60 FILMS

We report Raman spectroscopy studies for Rb3C60 films, which have been grown and measured, in situ, in an ultrahigh-vacuum chamber. We find interesting dependences of some of the vibrational modes on the excitation energy, and compare this with the corresponding optical transitions as measured by spectroscopic ellipsometry. Modes that show a strong interference with continuum excitations are enhanced for excitations corresponding to transitions involving the partially filled metallic band. Raman detection of external intermolecular modes are reported for both pure C60 and for Rb3C60. Some temperature dependence of these modes is observed, but no clear anomaly at the superconducting critical temperature could be determined. © 1994 The American Physical Society.