标题： 自下而上星际芳香环形成的终止 C6H5+ 显示英文标题

标题： Termination of bottom-up interstellar aromatic ring formation at C6H5+

摘要： 芳香分子苯被认为是在太空中更大的多环芳烃（PAHs）的基本构建块。 尽管苯在PAHs的形成中非常重要，但星际苯的形成机制尚不明确。 在模拟星际介质中苯的形成时，考虑了一个单一的离子-分子反应序列，从乙炔的质子化开始。 尽管这一过程已被用于模拟PAHs形成的初始步骤，但尚未进行实验测量。 为了探索这一反应机制，我们进行了首次在单碰撞条件下的乙炔质子化开始的顺序离子-分子反应的实验研究。 令人惊讶的是，我们发现该反应序列并未生成苯，而是终止于C6H5+，它对乙炔和氢气均无反应性。 这一结果推翻了之前提出的星际苯形成的机制，极大地改变了我们对星际PAH形成的理解。 显示英文摘要

摘要： The aromatic molecule benzene is considered the essential building block for larger polycyclic aromatic hydrocarbons (PAHs) in space. Despite benzene's importance in the formation of PAHs, the formation mechanisms of interstellar benzene are not well understood. A single ion-molecule reaction sequence is considered when modeling the formation of benzene in the interstellar medium, beginning with the protonation of acetylene. Although this process has been used to model the initial steps for formation of PAHs, it has not been experimentally measured. To explore this reaction mechanism, we have carried out the first experimental study of sequential ion-molecule reactions beginning with protonation of acetylene at single-collision conditions. Surprisingly, we find that the reaction sequence does not result in benzene and instead terminates at C6H5+, which is unreactive toward both acetylene and hydrogen. This result disproves the previously proposed mechanism for interstellar benzene formation, critically altering our understanding of interstellar PAH formation.