THE LUMO-DERIVED BAND OF THE CSC60 PHASES

The LUMO-derived band of the CsC60 compound was investigated by-means of x-ray and UV photoemission and photoelectric yield spectroscopies. A double-peak structure is found, with peak maxima at 1.1 eV and 0.35 eV. The relative magnitude of the two peaks is strongly temperature de pendent: a large transfer of spectral weight from the lower- to the hi gher-binding-energy peak takes place upon cooling to 110 K. The peaks are tentatively attributed to the dimer and the polymeric phase respec tively. However the behaviour as a function of temperature does not ag ree with the metastability of the dimer phase at room temperature. The position of the Fermi level is compatible with a correlated system on the border of the metal-insulating transition.