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 infrared absorption spectroscopy. Previous vibrational band assignments for a number of these clusters have been confirmed and new assignments for others have been made using a combination of isotopic (12C/13C) substitution and density functional (B3LYP/6-311G*) and ab initio (MP2) theoretical calculations. Reactions of neutral Cn (n = 1−9) and CmS (m = 6−0) fragments are shown theoretically to be highly exothermic. Evidence for such aggregation reactions in the formation of the clusters is found from isotopomeric band intensities. Given their calculated vibrational band intensities and estimated column densities, it is proposed that the direct observation via IR spectroscopy of C5S and SC5S clusters in the envelope of the carbon star, IRC+10216, and, possibly, the Taurus molecular clo...