Development of a photoionization spectrometer for accurate ion yield measurements from gaseous fullerenes

A photoionization spectrometer has been developed for measuring the ion yields for fullerenes in the photon energy range of 23–200 eV. Gaseous fullerenes were supplied from a high-temperature oven, ionized by irradiation of monochromatized synchrotron radiation, and detected after analysis with a time-of-flight mass spectrometer. The fluxes of the synchrotron radiation and fullerene beams were monitored concurrently with the acquisition of the ion signal counts in order to obtain reliable photoionization efficiency curves. The performance of the apparatus was examined by measuring the efficiency curve of C60+ produced from C60. The spectrum demonstrated better statistics than the previous results in the same photon energy region. Three distinct features were newly observed in the higher-energy side of the prominent resonance at ∼20 eV.