Laboratory studies on the hydrogen-deuterium substitution of hydrogen sulfide on ice surfaces at low temperatures.
Abstract
Hydrogen sulfide (H$ _{2}$S) is one of the representative sulfur-bearing molecules observed so far in the interstellar medium (ISM) and shows a high deuterium enrichment in that environment. Since the formation of H$ _{2}$S and its deuterated isotpologues (HDS and D$ _{2}$S) in the gas phase is energetically not favorable to occur in the ISM, it is generally considered that the hydrogen sulfides are formed by surface reactions on icy dusts. During the course of our recent researches on the chemical desorption of hydrogen sulfide (Oba et al. 2018, Nat. Astron. 2, 228), we observed the deuteration of H$ _{2}$S through the following hydrogen (H)-deuterium (D) substitution reactions on ice surfaces at low temperatures: H$ _{2}$S + D → HS + HD, HS + D → HDS. We then further studied the kinetics of the H-D substitution, as well as the D-H substitution of D$ _{2}$S by reactions with H atoms, on ice surfaces at low temperatures. We found the rate of the H-D substitution was comparable to that of the D-H substitution, which was in excellent agreement with a theoretical prediction.
- Publication:
-
43rd COSPAR Scientific Assembly. Held 28 January - 4 February
- Pub Date:
- January 2021
- Bibcode:
- 2021cosp...43E1912O