PRODUCTION AND FRAGMENTATION OF TANTALUM CARBIDE CLUSTER IONS

The production and fragmentation of tantalum carbide cluster ions, TaxCy+ (x = 1-11, y = 1-26), have been studied by Fourier transform mass spectrometry. The cluster ions were generated by direct laser vaporization of a variety of metal-and carbon-containing samples, and the results were compared with previous studies that used Knudsen effusion mass spectrometry for the production of metal carbides. A study using isotopically labeled precursors was performed to determine the origin of the carbon species present in the TaxCy+ ions. All results are consistent with a mechanism involving gas-phase recombination reactions in the laser-generated plasma for the production of the TaxCy+ ions. The low-energy collision-induced dissociation reactions are dominated by loss of neutral C3 and C10. The TaCy+ ions can be considered to be an ionic metal center attached to a carbon cluster having either a linear or cyclic structure. Bridging metal-carbido ligands are suggested to be important for the larger TaxCy+ ions.