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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[sup *] level have been performed for the cluster anions containing two carbon atoms, C[sub 2]S[sub m][sup -] (1≼m≼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. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Carbon/sulfur binary cluster anions with various compositions can be produced from laser vaporization of a sample mixed with sulfur and carbon powders in a 20:1 molar ratio. After mass-selection, their molecular formula was determined by collision-induced dissociation. The cluster anions consist of even carbon atoms only and their number of clustering sulfur atoms equals or exceeds that of carbon atoms. In this paper, we focus on mass spectrometry investigation and ab initio calculations on the cluster anions containing four carbon atoms, C[sub 4]S[sub m][sup -] (4≤m≤10). Geometry of various isomeric structures of the clusters was optimized at the ROHF/6-31G* level and their energies were compared to find the most stable isomers. The structures of C[sub 4]S[sub m][sup -] clusters computed in this paper were designed based on the structural features learned from the previous study on C[sub 2]S[sub m][sup -] and the results of mass spectrometry experiments. Among the structures, four low-lying forms with two dangling sulfur atoms and two closed rings have the lowest energy. Based on the experimental and theoretical investigations, a ring shrinkage scheme is proposed to account for the dissociation process of the binary cluster anions observed in the experiment. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A technique, laser vaporization by ablating at a solid target in the vapor phase, is developed to produce encapsulated titanium nanocrystals. By vaporizing sponge titanium in benzene vapor, the single titanium crystals encapsulated in carbon nanocages have been synthesized in good yields. The sizes of the encapsulated crystals are around 5-15 nm and the numbers of the wrapped graphitic layers are on the order of 3-10 layers. Characteristic lattice spacings and angles observed by high-resolution transmission electron microscopy identify two phases of the nanocrystals inside the carbon onion cavities as α-Ti and β-Ti. The latter has never been stable below 850 °C until the experiment. The encapsulated titanium crystals adsorbed a large amount of hydrogen released in the synthesis. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]