Title: Interaction of H2S with H atoms on grain surfaces under molecular cloud conditions

Authors: Julia C. Santos, Harold Linnartz, Ko-Ju Chuang

Summary: Hydrogen sulfide (H2S) is thought to be efficiently formed on the surfaces of interstellar dust grains. However, it has yet to be detected by astronomical observations. In this work, the fate of the elusive H2S ice is thoroughly investigated upon H-atom impact under molecular cloud conditions, providing a comprehensive analysis combined with detailed quantification of both the chemical desorption and ice chemistry that ensues. We confirm the formation of H2S2 via reactions involving H2S + H, and directly assess the chemical desorption of H2S by measuring the gas-phase desorption signals. The relative decrease of H2S ices by chemical desorption changes from ~85% to ~74% between temperatures of 10 and 16 K, while the decrease as the result of H2S2 formation is enhanced from ~5% to ~26%, suggesting an increasingly relevant sulfur chemistry induced by HS radicals at warmer environments.