Absolute Total Photoionization Cross Section of C60 in the Range of 25–120 eV: Revisited

The absolute total photoionization cross section σ abs,I of gaseous C 60 is measured in the photon energy h ν range from 25 to 120 eV by photoionization mass spectrometry with synchrotron radiation. The absolute detection efficiencies of photoions in different charge states are evaluated. The present σ abs,I curve is combined with the photoabsorption cross section curves of C 60 at h ν=3.5–26 eV in the literature, after appropriate alterations of the vapor pressure are taken into account. The oscillator strengths are computed from the composite curve to be 178.5 and 230.5 for the h ν ranges from 3.5 to 40.8 eV and from 3.5 to 119 eV, respectively. These oscillator strengths agree well with those expected from the Thomas–Kuhn–Reiche sum rule and 60 times the photoabsorption cross section of a carbon atom. Moreover, the present σ abs,I curve behaves similarly to the relative photoionization cross section curve reported by Reinkoster et al.