A chemical dynamics study on the gas phase formation of thioformaldehyde (H ₂ CS) and its thiohydroxycarbene isomer (HCSH)

Abstract

Significance Since the detection of carbonyl monosulfide (CS) in star-forming regions, about 200 molecules as complex as fullerenes have been detected in interstellar and circumstellar environments, but the formation routes to organosulfur molecules have remained essentially elusive. Exploiting thioformaldehyde (H 2 CS) and its thiohydroxycarbene isomer (HCSH), we deliver compelling testimony via laboratory experiments, electronic-structure theory, astrochemical modeling, and quasi-classical trajectory studies that these organosulfur species can be efficiently formed in star-forming regions such as Sagittarius B2 through bimolecular reactions involving hydrogen sulfide and methylidyne radicals. These elementary mechanisms are of fundamental importance to aid our understanding of how carbon and sulfur chemistries are connected in deep space, thus expanding our view on the sulfur cycle in the Galaxy.