Electronic structure of undoped and doped fullerenes

Summary form only given. The electronic structure o doped and undoped fullerenes M/sub x/C/sub n/ (M = Li, Na, K, Rb, Cs, Ca; n = 60, 70, 76, 84) has been investigated by electron energy-loss spectroscopy (EELS) in transmission and by high-resolution photoemission spectroscopy (PES). From Cls core-level excitation data the unoccupied /spl pi/* derived density of states has been investigated, and a filling of LUMO upon doping (and of LUMO+1 in Ca/sub x/C/sub 60/) is directly observed. In momentum dependent low-energy EELS data, optically allowed and forbidden /spl pi/ /spl rarr/ /spl pi/* transitions were observed. Comparisons are drawn between the PES spectra of these higher fullerenes, C/sub 60/ and their doped counterparts. Further investigation on the conduction band of K/sub 3/C/sub 60/ are reported in a second contribution.