发表机构
University of Firat; Gdańsk University of Technology; Instituto de Física Fundamental (IFF-CSIC); Nicolaus Copernicus University in Torun（Firat大学; 格但斯克理工大学; 基础物理研究所（IFF-CSIC）; 托伦哥白尼大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过高精度从头计算与统计方法，计算了Na、Mg、Al阳离子与碳链自由基的辐射缔合速率系数，并纳入IRC+10216化学模型。结果显示MgC4H+、MgC6H+和MgC5N+丰度与观测一致，支持辐射缔合形成机制，而MgC3N+及Na、Al加合物丰度偏低。
AI 中文摘要
含镁阳离子 MgC$_4$H$^+$、MgC$_6$H$^+$、MgC$_3$N$^+$ 和 MgC$_5$N$^+$ 最近在富碳包层 IRC+10216 中被观测到。这些物种被认为是通过 Mg$^+$ 与相应的中性自由基之间的辐射缔合形成的。本工作旨在确定 Al$^+$、Mg$^+$ 和 Na$^+$ 阳离子与碳链自由基反应的辐射缔合速率系数，以评估每种金属的含金属碳阳离子的相对重要性。为此，我们使用统计方法结合高精度的从头计算来获得辐射缔合速率系数。此外，考虑了超越一维捕获模型的各向异性效应，为模拟过程提供了更可靠的描述。在本工作中考虑的新限制条件下，计算了形成 Mg-、Al- 和 Na-C$_6$H$^+$ 以及 MgC$_4$H$^+$、MgC$_3$N$^+$ 和 MgC$_5$N$^+$ 的辐射缔合速率系数。这些新的速率系数被纳入富碳 AGB 包层 IRC+10216 的化学模型中。MgC$_4$H$^+$、MgC$_6$H$^+$ 和 MgC$_5$N$^+$ 的丰度与观测结果一致，差异不超过一个数量级，证实了辐射缔合是这些加合物的一种可能形成机制。然而，计算得到的 MgC$_3$N$^+$ 丰度比观测值低约两个数量级，这表明该物种的化学性质与其他物种显著不同，或者计算的速率系数过低。Na-C$_6$H$^+$ 和 Al-C$_6$H$^+$ 的丰度比 Mg 的丰度低约两个数量级，这使得在 IRC+10216 中探测类似的含金属阳离子变得非常困难。
英文摘要
The Mg-bearing cations MgC$_4$H$^+$, MgC$_6$H$^+$, MgC$_3$N$^+$, and MgC$_5$N$^+$ have been recently observed in the carbon-rich envelope IRC\,+10216. These species are thought to form upon radiative association between Mg$^+$ and the corresponding neutral radical. This work aims to determine the radiative association rate coefficients for the cations Al$^+$, Mg$^+$, and Na$^+$ reacting with carbon chain radicals to estimate the relative importance of metal-bearing carbon cations for each of these metals. For this purpose we use statistical methods in combination with highly accurate ab initio calculations to obtain the radiative association rate coefficient. Moreover, anisotropic effects beyond mono-dimensional capture model are considered, providing a more reliable description of the simulated processes.} The radiative association rate coefficients to form Mg-, Al- and Na-C$_6$H$^+$, as well as MgC$_4$H$^+$, MgC$_3$N$^+$, and MgC$_5$N$^+$, are calculated with the new restrictions considered in this work. These new rate coefficients are included in a chemical model of the C-rich AGB envelope IRC\,+10216. The abundances of MgC$_4$H$^+$, MgC$_6$H$^+$, and MgC$_5$N$^+$ are consistent with observations, with differences no greater than one order of magnitude, corroborating radiative association as a plausible formation mechanism for these adducts. However, the calculated abundance of MgC$_3$N$^+$ is about two orders of magnitude lower than observed, which indicates that either the chemistry of this species is significantly different from the others or the calculated rate coefficient is too low. The abundances obtained for Na-C$_6$H$^+$ and Al-C$_6$H$^+$ are around two orders of magnitude lower than for Mg, making very difficult to detect the analogous metal-bearing cations in IRC\,+10216.
Comments11 pages, 8 figures
