冰作为光化学屏蔽：在TMC-1中HCSCN和HCSCCH的吸附能学和光谱调制
Ice as a Photochemical Shield: Adsorption Energetics and Spectroscopic Modulation of Interstellar Thiocyanates HCSCN and HCSCCH in TMC-1
AI总结：
研究通过计算分析HCSCN和HCSCCH在固态水上的吸附能学，揭示其在星际硫库存中的行为，发现其在冰中存在复杂的吸附环境及光谱调制效应。
摘要：
最近在TMC-1中检测到硫代乙腈（HCSCN）和丙炔硫醇（HCSCCH）提供了星际硫库存的重要见解，但它们在尘埃颗粒外壳上的封存和生存性仍不明确。本文通过计算研究HCSCN和HCSCCH在非晶固态水（ASW）上的位点特异性吸附，利用水簇（H2O）n（n=6-16）在wB97X-D/def2-TZVP理论水平上建模，并通过QTAIM拓扑分析和TD-DFT垂直激发验证。结果表明存在高度异质的结合环境，脱附能跨度为1500至4900 K。强结合的空腔位点导致C=S伸缩振动的显著斯托克效应。关键发现是，尽管冰基质对紫外过渡波长的溶剂化色移影响微弱，但深结合的CN-空腔构型表现出显著的超色效应。将这些位点特异性参数应用于UCLCHEM气体-颗粒代码，表明这些物种经历的是逐渐的热脱附曲线而非单一的升华事件。此外，超色效应建立了生存悖论：虽然深陷的群体在热脱附方面被热力学屏蔽，但它们同时具有增强的紫外吸收截面，使其在升华之前易受星际辐射场的光解作用。
英文摘要：
The recent detections of thioformyl cyanide (HCSCN) and propynethial (HCSCCH) in TMC-1 provide critical insights into the interstellar sulfur inventory, yet their sequestration and survivability on dust grain mantles remain poorly constrained. Here, we present a computational study of the site-specific adsorption of HCSCN and HCSCCH on amorphous solid water (ASW), modelled via water clusters (H2O)n, n = 6-16, at the wB97X-D/def2-TZVP level of theory, corroborated by QTAIM topological analyses and TD-DFT vertical excitations. Our results reveal a highly heterogeneous binding environment, with desorption energies spanning 1500 to 4900 K. Strongly bound cavity sites induce significant Stark shifts in the C=S stretching modes. Crucially, while the ice matrix exerts a negligible solvatochromic shift on UV transition wavelengths, deeply bound CN-cavity configurations exhibit a pronounced hyperchromic enhancement of the oscillator strength. Implementing these site-specific parameters into the UCLCHEM gas-grain code demonstrates that these species undergo a gradual thermal desorption profile rather than a singular sublimation event. Furthermore, the hyperchromic effect establishes a Survival Paradox: while deeply trapped populations are thermodynamically shielded against thermal desorption, they simultaneously possess enhanced UV absorption cross-sections, rendering them vulnerable to photodissociation by the interstellar radiation field prior to sublimation.
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