星际硫代乙醛（CH₃CHS）的形成（气相和冰面机制，涉及次级硫产物）
Interstellar Formation of Thioethanal (CH$_{3}$CHS). Gas-Phase and Ice-Surface Mechanisms involving Secondary Sulfur Products
AI总结：
研究揭示了星际介质中硫代乙醛的形成机制，指出硫化学在低温度下通过气相和冰面路径生成，同时探讨了次级硫产物对产物产量的影响。
摘要：
硫化物在星际介质中的形成途径对于理解冷分子云中的星化学过程以及了解这些区域的硫预算至关重要。我们旨在探索最近检测到的硫代乙醛（CH₃CHS）的形成机制，以硫代乙醇（CH₃CH₂SH）作为前体，以及次级硫产物。采用气体相和冰粒表面环境中的电子结构方法和密度泛函理论。为了模拟星际冰层，我们使用中等（W6）和大无定形（W22）水簇，如在结合能评估协议中所实施的。在低温度星际条件下，识别出硫代乙醛形成机制在气相中是无能障的。表面环境以特定位点的方式调节活化能垒，通过Langmuir-Hinshelwood和Eley-Rideal引发的表面反应路径来阐明。与氧类似物相比，硫化学由于S-H键较弱，允许替代路径，在冰粒表面形成乙烷-1,1-二硫醇（CH₃CH(SH)SH），这可能减少硫代乙醛的产量。此外，首次准确报告了硫代乙醇在水冰上的结合能，证实其比乙醇更易挥发。所提出的机制提供了对TMC-1、Orion和Sgr B2(N)中CH₃CH₂SH和CH₃CHS似乎相互排斥检测的初步假设，这需要通过定量星化学建模进一步验证，并区分这种化学差异与观测灵敏度限制。这些定性发现突显了星际介质中含硫有机物的多面化学行为，并支持CH₃CH(SH)SH作为有前途的星化学目标。
英文摘要：
The formation pathways of sulfur-bearing species in the interstellar medium are crucial to understand astrochemical processes in cold molecular clouds and to gain new insights about the sulfur budget in these regions. We aim to explore the recently detected, thioethanal (CH$_{3}$CHS) formation mechanisms from thioethanol (CH$_{3}$CH$_{2}$SH) as a precursor in addition to secondary sulfur products. The electronic structure methods and density functional theory for both gas-phase and ice-grain surface environments is employed. To mimic interstellar ice-mantles, we use medium (W6) and large amorphized (W22) water clusters as implemented in Binding Energy Evaluation protocol. A barrierless formation mechanism for CH$_{3}$CHS under low-temperature interstellar conditions is identified, in the gas phase. Surface environments modulate activation barriers in a site-specific manner, elucidated through both Langmuir-Hinshelwood and Eley-Rideal initiated surface reaction pathways. Compared to oxygen analogs, sulfur chemistry enables alternate pathways due to weaker S-H bonding, with a competing route forming ethane-1,1-di-thiol (CH$_{3}$CH(SH)SH), on the ice-grain surface, potentially reducing CH$_{3}$CHS yields. The first accurate binding energy for thioethanol on water ice is also reported, confirming its greater volatility than ethanol. The proposed mechanism offers a tentative hypothesis for the apparent mutual exclusive detections of the CH$_{3}$CH$_{2}$SH and CH$_{3}$CHS in TMC-1, Orion, and Sgr B2(N), that further requires validation through quantitative astrochemical modeling and also to distinguish this chemical differentiation from observational sensitivity limitations. These qualitative findings highlight the multifaceted chemical behavior of sulfur-bearing organics in the interstellar medium and support CH$_{3}$CH(SH)SH as promising astro-chemical targets.
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