IONIZATION OF C-60 - IS IT TEMPERATURE-DEPENDENT

In a recent paper, Drewello et al. [T. Drewello, W. Kratschmer, M. Fie ber-Erdmann and A. Ding, Int. J. Mass Spectrom. lon Processes, 124 (19 93) R1] reported a temperature dependent ionisation cross section for the formation of C-60(2+) in their photoionisation dynamic studies on C60 using synchrotron radiation. To check this, the ratio of ion inten sities of C-60(2+) to that of C60 was determined as a function of temp erature of C60 samples using a Knudsen effusion mass spectrometer. Our results indicate the absence of any temperature dependence of cross s ection for the formation of C-60(2+) in the temperature range of measu rement (600-800 K) using electron impact ionisation.