Ultraviolet photoelectron spectra of C-100, C-110, and potassium-doped C-110

Ultraviolet photoelectron spectra of higher fullerenes C-100 and C-110 have been measured with a synchrotron radiation light source. The photoelectron onset energy of pristine C-110 is 0.75 eV below the Fermi level (E-F), whi ch is the smallest value among the pristine fullerenes reported so far. The spectra show intensity oscillation upon the incident photon energy change, as do those of other fullerenes. A spectral change upon potassium doping h as been observed with hv = 20 and 40 eV incident photon energies. The appea rance of a state between the first band of higher fullerenes and the Fermi level is observed in the hv = 20 eV spectra upon potassium doping. The onse t position of the new state moves toward the EF. In the case of the potassi um doping of C-110, the spectral onset begins just at the E-F, which indica tes its possibility of semimetallic nature. When C-110 is heavily doped wit h potassium the lower binding energy bands above 5 eV become faint, and thr ee structures simultaneously appear between 5 and 14 eV and become distinct . As these structures are considered to be of sigma-electron origin, heavy potassium doping may correspond to reconstruction of the fullerene cage or decomposition of the cage structure. [S0163-1829(99)04931-0].