Vibrational cooling in a cold ion trap: Low-temperature photoelectron spectroscopy of fullerene anions

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Hin-Koon Woo, hin-koon.woo@pnl.gov, Xue-Bin Wang, xuebin.wang@pnl.gov, and Lai-Sheng Wang, ls.wang@pnl.gov. Department of Physics, Washington State University, 2710 University Drive, Richland, WA 99354
Low-temperature photoelectron spectra were obtained for fullerene [C60-, C70-, and C702-] and fullerene oxides [C60Ox- (x = 1 3)] anions. Vibrational cooling of the anions in an ion trap yielded vibrationally resolved spectra and accurate electron affinities (EA's) for neutral C60, and C70, and the second EA of C70. The first and second EA's of C70 were respectively measured as 2.765 ± 0.010 eV and 0.02 ± 0.02 eV, establishing that C702- is an electronically stable dianion in the gas phase. The difference between the first and second EA (2.75 eV) provides a direct experimental measure for the onsite coulomb and exchange interactions between the two excess electrons in C702-. For fullerene oxides, the photoelectron spectra reveal one isomer for C60O-, two isomers for C60O2- and multiple isomers for C60O3-.