Zanchet Alexandre, Chen-Qiu Jia Lei, Larregaray Pascal, Bonnet Laurent, Romanzin Claire, Solem Nicolas, Thissen Roland, Alcaraz Christian
Instituto de Física Fundamental, CSIC, Serrano 123, Madrid 28006, Spain.
Departamento de Química Inorgánica, Universidad Autonoma de Madrid, Madrid 28049, Spain.
ACS Earth Space Chem. 2025 Feb 17;9(3):738-745. doi: 10.1021/acsearthspacechem.4c00391. eCollection 2025 Mar 20.
Endothermic reactions such as ( ) + are not expected to play a significant role in the chemistry of the interstellar medium (ISM). However, in some specific environments, such as photon-dominated regions (PDR), UV radiation may catalyze the reaction by providing enough internal energy to reactants to overcome endothermicity. For instance, it was recently shown that the vibrational excitation of H greatly enhances the reactivity of C and S with H, explaining the presence of their respective hydrides CH and SH in these regions. However, vibrational excitation of H is not a unique way to enhance the reactivity by UV radiation. Electronic excitation is an alternative way to effectively inject a huge amount of internal energy into the system, thus favoring reactivity. In this work, we will address how electronic excitation of the sulfur cation can strongly enhance the production of SH. This is done by measuring experimentally the cross section of the title reaction for collision energies from 50 meV up to several eV and comparing the results with theoretical predictions in the 0.001-3 eV range. The reaction cross section is then used to derive the rate constant for a wide range of temperatures.
诸如（ ）+ 这样的吸热反应预计在星际介质（ISM）的化学过程中不会起重要作用。然而，在一些特定环境中，如光子主导区域（PDR），紫外线辐射可能通过为反应物提供足够的内能以克服吸热性来催化反应。例如，最近的研究表明，H的振动激发极大地增强了C和S与H的反应活性，解释了这些区域中它们各自的氢化物CH和SH的存在。然而，H的振动激发并不是通过紫外线辐射增强反应活性的唯一方式。电子激发是一种将大量内能有效注入系统的替代方式，从而有利于反应活性。在这项工作中，我们将探讨硫阳离子的电子激发如何强烈增强SH的产生。这是通过实验测量标题反应在50毫电子伏特至几电子伏特碰撞能量下的截面，并将结果与0.001 - 3电子伏特范围内的理论预测进行比较来完成的。然后，反应截面被用于推导广泛温度范围内的速率常数。
