Gao Xiao-Fei, Xie Jing-Chen, Li Hao, Meng Xin, Wu Yong, Tian Shan Xi
Hefei National Laboratory for Physical Sciences at the Microscale, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Department of Chemical Physics, University of Science and Technology of China, Hefei, China.
Institute of Applied Physics and Computational Mathematics, Beijing, China.
Commun Chem. 2021 Feb 10;4(1):13. doi: 10.1038/s42004-021-00450-0.
The cyanide anion (CN) has been identified in cometary coma, interstellar medium, planetary atmosphere and circumstellar envelopes, but its origin and abundance are still disputed. An isolated CN is stabilized in the vibrational states up to ν = 17 of the electronic ground-state Σ, but it is not thought to survive in the electronic or vibrational states above the electron autodetachment threshold, namely, in superexcited states. Here we report the direct observation of long-lived CN yields of the dissociative electron attachment to cyanogen bromide (BrCN), and confirm that some of the CN yields are distributed in the superexcited vibrational states ν ≥ 18 (Σ) or the superexcited electronic states Σ and Π. The triplet state can be accessed directly in the impulsive dissociation of BrCN or by an intersystem transition from the superexcited vibrational states of CN. The exceptional stability of CN in the superexcited states profoundly influences its abundance and is potentially related to the production of other compounds in interstellar space.
氰化物阴离子（CN）已在彗星彗发、星际介质、行星大气和恒星周包层中被发现，但其起源和丰度仍存在争议。孤立的CN在电子基态Σ的振动状态下稳定至ν = 17，但人们认为它在高于电子自脱离阈值的电子或振动状态下，即在超激发态下无法存活。在此，我们报告了对溴化氰（BrCN）解离电子附着产生的长寿命CN产率的直接观测，并证实部分CN产率分布在超激发振动状态ν≥18（Σ）或超激发电子状态Σ和Π中。三重态可在BrCN的脉冲解离中直接获得，或通过CN超激发振动状态的系间跃迁获得。CN在超激发态下的异常稳定性深刻影响其丰度，并可能与星际空间中其他化合物的产生有关。
