COLLISION-INDUCED DISSOCIATION OF VANADIUM-CARBON CLUSTER CATIONS

Collision-induced dissociation (CID) studies of vanadium-carbon cluste rs were made employing a triple quadrupole mass spectrometer system co upled with a laser vaporization source. The results reveal that the pr imary dissociation channel is loss of a metal atom for all but V8C14+, which loses C-3, and V9C14+ which loses both V and VC2. These finding s are in general agreement with earlier ones reported for the titanium system, except that under single-collision conditions V8C14+ loses a C-3 unit to become V8C11+, while Ti8C14+ loses Ti. Importantly, we sho w that both the met-car V8C12+ and V8C13+ are significantly more resis tant to dissociation than the neighboring V8C11+ cluster species. In a ddition to reporting the primary fragmentation products of several VxC y+ clusters, we also present the results of studies of the multiple-co llision dissociation patterns of both V8C12+ and V8C13+, which are obs erved to undergo C-2 and C-3 loss after some metal loss has occurred. These findings are consistent with the building patterns observed for these clusters and our proposed structure for V8C12+. Through study of the dissociation of V9C12+, the ionization energy of V8C12 is found t o be less than that of the vanadium atom, i.e., less than 6.74 eV, in accord with theoretical predictions.