论文标题
星际环境中的异构体（i）：z-和e-e-cyanomethanimine的情况
Isomers in Interstellar Environments (I): The Case of Z- and E-Cyanomethanimine
论文作者
论文摘要
在这项工作中，我们介绍了我们研究Z-和e-氨基甲胺（HNCHCN）化学的结果，这两种都可能是核碱腺嘌呤的前体。从头静脉量的化学计算进行了许多与原子氢反应的量子化学计算。我们发现，反应H + Z/E-HNCHCN导致H型和H $ _2 $ -Abstraction通过类似的短距离屏障进行，并在$ \ sim10^{ - 17} $ cm $ cm $^{3} $ s $ s $ s $^{ - 1} $的订单下进行双分子速率系数。然后将这些结果纳入天体化学模型中，并用于巨型分子云G+0.693的模拟中。将从这些模型获得的计算出的丰度与以前的观察数据进行了比较，并发现非常一致，预计[z/e]比率为$ \ sim3 $ - 略小于先前派生的$ 6.1 \ pm2.4 $。我们发现，模拟中的[z/e]比率主要是由于两个构象异构体的不同永久性偶极子驱动的离子分子破坏率。基于这些结果，我们提出了一个通用的统一规则，用于估计星际环境中异构体的丰度。
In this work, we present the results of our investigation into the chemistry of Z- and E-cyanomethanimine (HNCHCN), both of which are possible precursors to the nucleobase adenine. Ab initio quantum chemical calculations for a number of reactions with atomic hydrogen were carried out. We find that the reaction H + Z/E-HNCHCN leading both to H-addition as well as H$_2$-abstraction proceed via similar short-range barriers with bimolecular rate coefficients on the order of $\sim10^{-17}$ cm$^{3}$ s$^{-1}$. These results were then incorporated into astrochemical models and used in simulations of the giant molecular cloud G+0.693. The calculated abundances obtained from these models were compared with previous observational data and found to be in good agreement, with a predicted [Z/E] ratio of $\sim3$ - somewhat smaller than the previously derived value of $6.1\pm2.4$. We find that the [Z/E] ratio in our simulations is due mostly to ion-molecule destruction rates driven by the different permanent dipoles of the two conformers. Based on these results, we propose a general rule-of-thumb for estimating the abundances of isomers in interstellar environments.
