Studies on carbon/sulfur cluster anions produced by laser vaporization: Experiment (collision-induced dissociation) and theory (ab initio calculation) I C2Sm- (1 <= m <= 11)

Binary cluster anions composed of carbon and sulfur atoms have been produced from laser vaporization of a sample mixed with sulfur and carbon powders in a 20:1 ratio. They were mass-selected and their molecular formula was determined by collision-induced dissociation. The clusters consist of even carbon atoms only and their number of clustering sulfur atoms equals or exceeds that of carbon atoms. Ab initio calculations at the ROHF/6-31G* level have been performed for the cluster anions containing two carbon atoms, C2Sm- (1 less than or equal to m less than or equal to 10). Geometries of various isomeric structures of the clusters were optimized and their energies were compared to find the most stable isomers. For the singly charged anions, attachment of an additional electron leads to break their sulfur rings, and the isomers with two dangling sulfur atoms and a closed ring have the lowest energy. According to the experimental and theoretical investigations, the two carbon atoms form the bone of the clusters, and ejection of two sulfur atoms is the most competitive dissociation pathway of the cluster anions. (C) 2000 American Institute of Physics. [S0021-9606(00)00421-9]