LASER-INDUCED PLASMA REACTIONS OF TRANSITION-METALS WITH HYDROCARBON - FROM CLUSTERS TO MICROCRYSTALS

Laser vaporization of transition metals (Ti, V, Nb, Ta, Mo, and MT) and reactions with small hydrocarbons (CH4 and C2H4) were observed with a TOF mass spectrometer. The measured results of VC and Ti-C clusters indicate that met-cars and some clusters with atom ratios of 1:2 (metal to carbon) coexist in the product, and metcars with one or two enclosed carbon atoms in the cages can be assumed for the nearly as intense satellite Lines (M(8)C(13) and M(8)C(14)). The typical magic numbers for TaC and NbC microcrystals with rocksalt-like fee structure were measured. Carbon atoms adsorbed on TaC and NbC microcrystals show different features: There is some interaction among the adsorbed carbon atoms. In the mass spectrum of NbC clusters, met-cars with single- and double-cage structures were identified. No significant magic numbers were observed for MoC and WC clusters. The ratio of metals to carbon atoms is 1:1 for Mo and 2:1 for W.