发表机构
Institute of Low Temperature Science, Hokkaido University; Department of Chemistry, Hiroshima University; Departamento de Astrofísica Molecular, Instituto de Física Fundamental, CSIC; RIKEN Pioneering Research Institute（北海道大学低温科学研究所; 广岛大学化学系; 西班牙国家研究委员会基础物理研究所分子天体物理学部; 理研先锋研究机构）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
实验发现硫原子在硅酸盐表面强化学吸附且热不可逆，模型表明至少10%的硫被锁定，为分子云“缺失硫”问题提供物理解释。
AI 中文摘要
星际介质中的硫（S）化学因长期存在的“缺失硫”问题而仍受约束不足，其中分子云中宇宙硫的相当大比例仍未确定。为全面理解星际介质中的硫化学，必须阐明其在星际尘埃颗粒上的行为。在此，我们实验研究了模拟星际分子云条件下硫原子的表面基元过程。我们的原位激光检测方法能够直接追踪吸附在天体物理相关硅酸盐基底和无定形固态水（ASW）上的硫原子。我们发现硫原子强化学吸附于硅酸盐表面，即使在ASW升华后仍保持结合，使其在观测上不可见。结合这些结果的星化学模型表明，分子云中总硫预算的至少10%必须锁定在硅酸盐尘埃颗粒上。我们的结果确定了硅酸盐上的硫化学吸附是驱动硫消耗的关键机制，并为缺失硫问题提供了物理解释。
英文摘要
Sulfur (S) chemistry in the interstellar medium remains poorly constrained due to the longstanding "missing sulfur" problem, where a significant fraction of cosmic sulfur in molecular clouds remains unidentified. To gain a comprehensive understanding of S chemistry in the interstellar medium, its behavior on interstellar dust grains must be clarified. Here, we experimentally investigated the surface elementary processes of S atoms under conditions mimicking interstellar molecular clouds. Our in-situ laser-based detection method enabled the direct tracking of S atoms adsorbed on astrophysically relevant silicate substrates and amorphous solid water (ASW). We found that sulfur atoms strongly chemisorbs onto silicate surfaces and remains bound even after ASW sublimation, rendering it observationally invisible. An astrochemical model coupled with these results suggests that at least 10 percent of the total sulfur budget in molecular clouds must be locked onto silicate dust grains. Our results identify sulfur chemisorption on silicate as a key mechanism driving sulfur depletion and provide a physical explanation for the missing sulfur problem.
CommentsAccepted for publication in ApJ; 25 pages, 9 figures, 1 table
