RESONANCE EFFECTS OBSERVED IN THE INTERACTION OF LOW-ENERGY ELECTRONSAND INTRAMOLECULAR VIBRATIONS OF SOLID C-70

The intramolecular vibrations of a thick epitaxial C-70(111) film on G eS(001) have been measured by high-resolution electron energy-loss spe ctroscopy (HREELS). A negative-ion resonant behavior is observed in th e energy dependence of the impact scattering differential cross sectio ns. These resonances are described as electronic excitation associated shape resonances, which are coincident with the electron energy loss and free-electron capture experiments. Finally, the effect of charge t ransfer on the resonance behavior is discussed through the comparison of bulk spectra with those from an adsorbed monolayer of C-70 on Au(11 0).