Successive H-atom Addition to Solid OCS on Compact Amorphous Solid Water

Carbonyl sulfide (OCS) is an abundant sulfur (S)-bearing species in the interstellar medium. It present not only gas phase, but also on grains as a solid; therefore, OCS very likely undergoes physicochemical processes icy surfaces at low temperatures. The study experimentally and computationally investigates reaction of solid with hydrogen (H) atoms amorphous water results show that addition H to proceeds via quantum tunneling, further leads formation carbon monoxide (CO), (H2S), formaldehyde (H2CO), methanol (CH3OH) thioformic acid (HC(O)SH). These experimental are explained by our chemical calculations, which demonstrate initial S atom most predominant, leading OCS-H radicals. Once formed radical stabilized ice, yields CO H2S, while C HC(O)SH. We have confirmed, separate experiment, HC(O)SH HCO reactions SH would important implication for recent detection toward G+0.693-0.027.