ELECTRON-IMPACT IONIZATION OF C-60 AND C-70 - PRODUCTION AND PROPERTIES OF PARENT AND FRAGMENT IONS STUDIED WITH A 2-SECTOR FIELD MASS-SPECTROMETER

Electron impact ionization and dissociation studies of C-60 and C-70 c arried out in our laboratory over the past three years have revealed m any exciting and novel features of this new class of molecules (cluste rs). The most salient results are summarized in this paper, including first a description of the crossed beams apparatus and the various mas s spectrometric (two-sector field) techniques used. This is followed b y a discussion of the production of parent and fragment ions (with up to eight charges) via electron impact ionization of C-60 and C-70 incl uding results on mass spectral fragmentation patterns and measured and calculated absolute ionization cross-section functions. The experimen tal results concerning the energetics of produced parent and fragment ions are presented in the next section and measured appearance energie s and breakdown curves are analysed in the frame of various theoretica l concepts (RRKM, FHBT) thereby allowing us to derive the correspondin g binding energies. The last section is devoted to (i) the different a spects of the stability of singly- and multiply-charged fullerene ions (i.e. the quantitative study of various unimolecular decay channels s uch as monomer evaporation, sequential decay series, charge separation reactions, etc.) and, based on the measured properties of these decay reactions, to (ii) a discussion of the possible decay mechanisms.