Ugelow Melissa S, Wieman Scott T, Schwarz Madeline C R, Da Poian Victoria, Stern Jennifer C, Trainer Melissa G
NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, United States.
Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, United States.
ACS Earth Space Chem. 2024 Dec 5;8(12):2362-2371. doi: 10.1021/acsearthspacechem.4c00102. eCollection 2024 Dec 19.
Laboratory investigations of photochemical reactions in simulated Titan-like atmospheric systems provide insight into the formation of gas and aerosol products and the influence of different environmental parameters on the types of organic molecules generated. Studying the gas-phase products as a function of reaction time provides further insight into the reaction pathways that lead to organic production. The stable isotopes in the reactants and products serve as tracers and help to disentangle these reaction pathways. We report a time study on the chemical composition and relative abundance of the evolved gas-phase products formed by far-ultraviolet reactions between 5% CH and N in a closed system. Two experimental setups are used, where one fully removes hydrogen from the experimental system using a palladium membrane (hydrogen-poor experiments) and the other does not remove hydrogen during the experiment (hydrogen-rich experiments). Carbon isotope values (δC) of CH, CH, and CH are also reported and are used, along with the gas-phase composition and relative abundance measurements, to constrain the chemical reactions occurring during our experiments. The gas-phase products CH, CH, -CH, iso-CH, -CH, iso-CH, CH, CH, HCN, and CHCN were detected, with some variations between both sets of experiments. The hydrogen-poor experiments highlight the importance of hydrogen in the formation of HCN, -CH, iso-CH, and CHCN. By monitoring the chemical composition and the carbon isotopic ratios of the gas phase during CH/N photochemistry, especially under a hydrogen-poor and hydrogen-rich environment, the photochemical reaction pathways and the influence of hydrogen on these pathways in a Titan-like atmosphere can be better understood.
对类似土卫六的大气系统中的光化学反应进行实验室研究，有助于深入了解气体和气溶胶产物的形成，以及不同环境参数对所生成有机分子类型的影响。研究气相产物随反应时间的变化，能进一步洞察导致有机产物生成的反应途径。反应物和产物中的稳定同位素可作为示踪剂，有助于理清这些反应途径。我们报告了一项关于在封闭系统中5%的甲烷和氮气之间的远紫外反应所形成的气相产物的化学成分和相对丰度的时间研究。使用了两种实验装置，一种使用钯膜从实验系统中完全去除氢气（贫氢实验），另一种在实验过程中不去除氢气（富氢实验）。还报告了甲烷、乙烷和丙烷的碳同位素值（δC），并将其与气相组成和相对丰度测量结果一起用于限制我们实验过程中发生的化学反应。检测到了气相产物甲烷、乙烷、乙烯、异丁烯、乙炔、异戊二烯、丙炔、丙烯、氰化氢和乙腈，两组实验之间存在一些差异。贫氢实验突出了氢在氰化氢、乙烯、异丁烯和乙腈形成中的重要性。通过监测甲烷/氮气光化学过程中气相的化学成分和碳同位素比值，特别是在贫氢和富氢环境下，可以更好地理解类土卫六大气中的光化学反应途径以及氢对这些途径的影响。
