2019ApJ...874..124O

To elucidate the physico-chemical behavior of hydrogen sulfide (H₂S) on icy grains in dense molecular clouds, we investigated the surface reactions of solid H₂S with H and D atoms in low-temperature laboratory experiments. We confirmed that H₂S 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 H₂S with D atoms almost matched that for the D-H substitution of solid D₂S with H atoms. The present experimental results clearly suggest that the observed abundances of H₂S and its deuterated isotopologues (HDS and D₂S) in the interstellar medium are controlled, at least partly, by surface reactions on interstellar icy grains.