A C+60 ion beam was extracted from a hollow cathode ion source (model 911A). The mass spectra of 6 keV C60 and its fragments have been measured. Only those clusters with an even number of C atoms were observed and the largest one was C84. The result shows that the fragment ion beam has an exponential distribution, which is similar to that of C+60–H2(He) collision experiments. We also have extracted C-cluster negative-ion beams from a Middleton 860 sputtering source. With a graphite cathode, we have observed many cluster ions which were not previously reported. For a C60/C70 cathode, we have obtained a stable C−60 ion beam with current of about 1 nA. The spectra of the negative ions are complicated due to the existence of the Cs–Cn clusters.
A crossed-beam facility for electron impact ionization o f ions was constructed. The absolute cross sections for single ionization of Art and C 1 ' ions at electron energies ranging from 30 to 500eV were measured. The uncertainty is about &13%.
With a 30keV mini-separator at the accelerator laboratory o f Fudan University, we have successfully obtained about 1 nA fullerene ion beam. Under the same conditions, we have also observed the fragment ions (n=20-40). The Cz0 (Go) beams will be used study ~~l l i ~i ~i i between fullerene and electrons, atoms and photons.PACS: 07. 77. +p, 3G. 40. +d Since tlie discovery of fullerene and its ion in 1985,' there have been a large number of experimental and theoretical investigations about this soccer-ball shaped molecule. Several collision experiments have been reported. O'Brien et al.' studied tlie photon dissociation. At tlie collision energy bellow 10 keV, Young3 found that tlie fragineiitation of Ci0 occurs by loss of an even number of carbon atoiizs wlieii colliding with atoms. Singly charged fragment ions from collisioii betweeii Ci0 and 0 3 , according to Doyle et aJ.," are attributed to fragment of excited Ci0 from electron capture and subsequent dissociation. Compbell et aJe5 have measured tlie mass spectra from collisions between Ci0 and various target gases, they concluded that tlie fragmentation of Czo is a sort of fission. Hvelpluiid et al. found an exponential distribution of fragment ioiis when 50-300 keV Ci0 ions collide with H?(Ne) target gas.' In general, more detailed studies of tlie dynamics of tlie fragmentation are desirable to fully understand tlie structure of fullereiie.
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