Infrared absorption spectroscopy of small carbon-sulfur clusters isolated in solid Ar

Small asymmetric and symmetric carbon-sulfur clusters, CnS and SCnS (n = 1- 5), have been generated by pulsed laser ablation of a carbon/sulfur mixture , deposited in an argon matrix at 12 K, and studied via Fourier transform i nfrared absorption spectroscopy. Previous vibrational band assignments for a number of these clusters have been confirmed and new assignments for othe rs have been made using a combination of isotopic (C-12/C-13) substitution and density functional (B3LYP/6-311G*) and ab initio (MP2) theoretical calc ulations. Reactions of neutral C-n (n = 1-9) and CmS (m = 6-0) fragments ar e shown theoretically to be highly exothermic. Evidence for such aggregatio n reactions in the formation of the dusters is found from isotopomeric band intensities. Given their calculated vibrational band intensities and estim ated column densities, it is proposed that the direct observation via IR sp ectroscopy of C5S and SC5S clusters in the envelope of the carbon star, IRC +10216, and, possibly, the Taurus molecular cloud, TMC-1, is an attractive possibility.