硫代乙醛（CH3CHS）在星际冰表面：解开ISM中两个化学二分法的关键分子
Thioacetaldehyde (CH3CHS) on interstellar ices: a key molecule to unravel two chemical dichotomies in the ISM
- Instituto de Física Fundamental, CSIC（基础物理研究所，西班牙科学理事会）
- Center for Astrochemical Studies, Max-Planck-Institut für extraterrestrische Physik（星际化学研究中心，马克斯·普朗克地外物理研究所）
- Observatorio Astronómico Nacional (OAN)（国家天文台）
- Centro de Astrobiología, CSIC-INTA（天体生物学中心，西班牙科学理事会-国家航空航天技术研究所）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究通过探究硫代乙醛在星际冰上的氢化路径，解释了其与乙醛的丰度差异及在G+0.693-0.027中的缺失，揭示了冰表面化学在星际硫化学中的关键作用。
AI中文摘要：
硫代乙醛（CH3CHS）最近在TMC-1中被探测到，其丰度比其氧类似物乙醛（CH3CHO）低约36倍。这使得CH3CHS/CH3CHO对成为该云中已探测到的氧/硫类似物对中柱密度差异最大的一对。我们研究了CH3CHS的氢化路径，以解决ISM中的两个化学二分法：（i）CH3CHS与CH3CHO之间的差异，以及（ii）CH3CHS在G+0.693-0.027分子云中明显缺失，而乙硫醇（CH3CH2SH）在TMC-1中缺失。我们的结果揭示了一个涉及多个竞争反应的复杂方案，突出显示了一系列高效的连续氢化反应，可导致CH3CH2SH的生成。这一发现表明，在TMC-1中观察到的硫代乙醛的高S/O比（约36），在G+0.693-0.027中甚至更为显著（≥112），可能源于其在冰表面通过氢化反应转化，这与CH3CHO的情况相反，后者对该化学过程更具抵抗力。CH3CHS在冰上的直接氢化反应，即使在150 K的气相中也能发生，为其在G+0.693-0.027中未被探测到提供了可靠解释，在那里颗粒表面化学预计发挥重要作用，有利于将CH3CHS转化为CH3CH2SH，而CH3CH2SH确实在G+0.693-0.027中被探测到。相比之下，TMC-1代表了一个更原始的气相环境，颗粒表面化学的影响较低。在这些条件下，CH3CHS可以持续存在，而CH3CH2SH仍未被探测到。总体而言，我们的结果表明，完全不同的反应性促成了两个最大星际硫工厂的化学复杂性。
英文摘要：
Thioacetaldehyde (CH3CHS), recently detected in TMC-1, has an abundance approximately 36 times lower than its oxygen analog, acetaldehyde (CH3CHO). This makes the CH3CHS/CH3CHO pair the one with the largest column density difference among the detected oxygen/sulfur analogue pairs in this cloud. We investigate the hydrogenation pathways of CH3CHS to address two chemical dichotomies in the ISM: (i) the differenciation between CH3CHS and CH3CHO, and (ii) the apparent absence of both CH3CHS in the G+0.693-0.027 molecular cloud and ethyl mercaptan (CH3CH2SH), in TMC-1. Our results reveal a complex scheme that involves multiple competing reactions, highlighting an efficient sequence of consecutive hydrogenations that can lead to CH3CH2SH. This finding suggests that the high S/O ratio observed for thioacetaldehyde in TMC-1 (~36), and even more pronounced in G+0.693-0.027 ($\geq$112), may result from its conversion via hydrogenation on the ice surface, contrary to the case of CH3CHO, which is more resistant to that chemical process. The straightforward hydrogenation of CH3CHS on ices, which can also take place even in the gas-phase at 150 K, provides a reliable explanation for its non-detection in G+0.693-0.027, where grain-surface chemistry is expected to play an important role, favoring the conversion of CH3CHS into CH3CH2SH, which is indeed detected in G+0.693-0.027. In contrast, TMC-1 represents a more pristine gas-phase environment, where grain-surface chemistry has a lower impact. Under these conditions, CH3CHS can persist, while CH3CH2SH remains undetected. Overall, our results show the entirely different reactivity that contributes to the chemical complexity of two of the largest interstellar sulfur factories.
