We present accurate ab initio calculations on the structural properties of a gas-phase reaction of possible interest for Saturn’s outer atmosphere chemistry, in which the CH₂ molecule has been detected. In the present study, that molecule is made to react with the H^– anion to form the CH^– species, one considered as a possible intermediate in ionic processes networks. The results indicate that this reaction is markedly exothermic and proceeds with the formation of an intermediate, which occurs via only a shallow barrier below the reagents and progresses directly to the product region. The corresponding rate coefficients of reactions are also computed by making use of the variational transition state theory modeling and found to efficiently lead to the formation of the final anion even at the lower temperatures of interstellar medium conditions.

中文翻译：

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关于星际CH-阴离子的形成：CH2与H反应的机理和速率。

我们提出了可能对土星的外部大气化学感兴趣的气相反应的结构性质的准确的从头算，其中已检测到CH ₂分子。在本研究中，该分子被制成与H反应^-阴离子以形成CH ^-物种，一种被认为是离子过程网络中可能的中间体。结果表明该反应明显放热，并继续形成中间体，该中间体仅通过试剂下方的浅壁屏障发生，并直接进行至产物区域。还利用变迁过渡状态理论模型计算了相应的反应速率系数，发现即使在较低的星际介质条件下，也有效地导致了最终阴离子的形成。