Combined Crossed Molecular Beam and ab initio Investigation of the Formation of Carbon-Bearing Molecules in the Interstellar Medium via Neutral-Neutral Reactions

The crossed molecular beams reaction of atomic carbon C(3P with hydro- j) gen sulÐde, H allene, the vinyl radical, and deutero- 2S, H2CCCH2, C2H3 , acetylene, C have been studied at di erent collision energies up to 42.2 2HD, kJ mol~1 and combined with high level ab initio calculations. All reactions are barrier-less and are dominated by a carbonÈhydrogen exchange to form thioformyl (HCS), butatrienyl (HCCCCH isomer(s), and deuteriated 2), C3Htricarbon hydride(s). This carbonÈhydrogen repla2cement channel represents a one-step alternative reaction pathway to competing ionÈmolecule reactions to form complex, carbon-bearing molecules in the interstellar medium as well as in the outÑow of carbon stars.