Photofragmentation of C60 in valence ionization

The yield curves for C60−2n+ (n = 1-3) produced by photoionization of C60 are measured in the hv range of 25-150 eV. The appearance energies increase with increasing n. Evaluation is made on the upper limits of the internal energies of the primary C60+ above which C60−2n+2+ fragments (n ≥ 1) cannot escape from further dissociating into C60−2n+ + C2. These limits agree well with the theoretical internal energies of C60+ corresponding to the threshold for the formation of C60−2n+, on the assumption that the binding energies of C60−2n+2+ are equal to those proposed by Foltin et al. [M. Foltin, M. Lezius, P. Scheier, T.D. Märk, J. Chem. Phys. 98 (1993) 9624].