Physico-chemical Behavior of Hydrogen Sulfide Induced by Reactions with H and D Atoms on Different Types of Ice Surfaces at Low Temperature

Abstract

Abstract To elucidate the physico-chemical behavior of hydrogen sulfide (H 2 S) on icy grains in dense molecular clouds, we investigated the surface reactions of solid H 2 S with H and D atoms in low-temperature laboratory experiments. We confirmed that H 2 S was lost from the surface by reaction with H atoms via chemical desorption. We found no strong association between the effective desorption cross section and the ice structure (porous amorphous, non-porous amorphous, or crystalline) or temperature (10–30 K). At 10 K, the reaction rate constant for the H–D substitution of solid H 2 S with D atoms almost matched that for the D–H substitution of solid D 2 S with H atoms. The present experimental results clearly suggest that the observed abundances of H 2 S and its deuterated isotopologues (HDS and D 2 S) in the interstellar medium are controlled, at least partly, by surface reactions on interstellar icy grains.