PHOTOION SPECTRA OF C-60 MOLECULES AT RESONANCE EXCITATION AND IONIZATION ENERGIES NEAR THE C-1S EDGE

Photoionization dynamics of gas-phase C-60 molecules after selective e xcitation with synchrotron radiation has been studied with time-of-fli ght mass spectrometry. The energy level scheme deduced from previous p hotoelectron and Auger electron spectra is used to analyze the photoio n data. At the vicinity of pi pre-edge resonances the fragmentation o f multiply-charged ions varies strongly as a function of photon energy . The C-60(+) ion yield decreases slowly after Is threshold indicating that the slow photoelectrons can get recaptured. Somewhat further abo ve the threshold the enhanced relative fragmentation of the parent C-6 0(+) ions suggests excitation of the giant plasmon resonance due to 20 eV photoelectrons. (C) 1997 American Institute of Physics.