Zhou Zhengfang, Feng Shaowen, Hua Zefeng, Li Zhen, Chen Yang, Zhao Dongfeng
Hefei National Laboratory for Physical Sciences at the Microscale, and Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China.
J Chem Phys. 2020 Apr 7;152(13):134304. doi: 10.1063/1.5143848.
The dissociation dynamics of CO in the CΣ state has been studied in the 8.14-8.68 eV region by [1+1] two-photon excitation via vibronically selected intermediate AΠ and BΣ states using a cryogenic ion trap velocity map imaging spectrometer. The cryogenic ion trap produces an internally cold mass selected ion sample of CO . Total translational energy release (TER) and two-dimensional recoiling velocity distributions of fragmented CO ions are measured by time-sliced velocity map imaging. High resolution TER spectra allow us to identify and assign three dissociation channels of CO (CΣ ) in the studied energy region: (1) production of CO(XΣ) + O(P) by predissociation via spin-orbit coupling with the repulsive 1Π state; (2) production of CO(XΣ) + O(D) by predissociation via bending and/or anti-symmetric stretching mediated conical intersection crossing with AΠ or BΣ , where the CΣ /AΠ crossing is considered to be more likely; (3) direct dissociation to CO(AΠ) + O(P) on the CΣ state surface, which exhibits a competitive intensity above its dissociation limit (8.20 eV). For the first dissociation channel, the fragmented CO(XΣ) ions are found to have widely spread populations of both rotational and vibrational levels, indicating that bending of the parent CO over a broad range is involved upon dissociation, while for the latter two channels, the produced CO(XΣ) and CO(AΠ) ions have relatively narrow rotational populations. The anisotropy parameters β are also measured for all three channels and are found to be nearly independent of the vibronically selected intermediate states, likely due to complicated intramolecular interactions in the studied energy region.
利用低温离子阱速度成像光谱仪，通过振转选择的中间态AΠ和BΣ进行[1+1]双光子激发，在8.14 - 8.68 eV区域研究了CΣ态下CO的解离动力学。低温离子阱产生内部冷却的CO质量选择离子样品。通过时间切片速度成像测量碎片化CO离子的总平动能释放（TER）和二维反冲速度分布。高分辨率TER光谱使我们能够识别并确定研究能量区域内CO（CΣ）的三个解离通道：（1）通过与排斥性1Π态的自旋轨道耦合预解离产生CO（XΣ）+ O（P）；（2）通过弯曲和/或反对称拉伸介导的锥形交叉与AΠ或BΣ预解离产生CO（XΣ）+ O（D），其中CΣ/AΠ交叉被认为更有可能；（3）在CΣ态表面直接解离为CO（AΠ）+ O（P），在其解离极限（8.20 eV）以上表现出竞争强度。对于第一个解离通道，发现碎片化的CO（XΣ）离子在转动和振动能级上都有广泛分布的布居，表明母体CO在解离时涉及到宽范围的弯曲，而对于后两个通道，产生的CO（XΣ）和CO（AΠ）离子具有相对较窄的转动布居。还测量了所有三个通道的各向异性参数β，发现其几乎与振转选择的中间态无关，这可能是由于研究能量区域内复杂的分子内相互作用所致。
