Cross sections for photoionization of fullerene molecular ions Cn+ with n = 40, 50, 70, 76, 78, and 84

Author(s): Thomas, CM; Baral, KK; Aryal, NB; Habibi, M; Esteves-Macaluso, DA; Kilcoyne, ALD; Aguilar, A; Schlachter, AS; Schippers, S; Muller, A; Phaneuf, RA | Abstract: © 2017 American Physical Society. Absolute cross-section measurements are reported for single photoionization of Cn+ fullerene molecular ions (n=40, 50, 70, 76, 78, and 84) in the photon-energy range 18-70 eV. The experiments were performed by merging a mass and charge selected beam of Cn+ molecular ions with a beam of monochromatized synchrotron radiation and measuring the yield of Cn2+ product ions as a function of the photon energy. Oscillator strengths determined by integrating the measured cross sections over this energy range exhibit a linear dependence on n. The cross sections are parametrized by fits to three Lorentzian functions to represent plasmon excitations and a linear function for direct ionization. The highest-energy resonance in the data near 46 eV is similar to that previously observed in single photoionization of C60 and may be attributable to a harmonic of the dominant surface-plasmon resonance near 23 eV.