Li Zhenxing, Fu Yan-Lin, Luo Zijie, Yang Shuaikang, Wu Yucheng, Wu Hao, Wu Guorong, Zhang Weiqing, Fu Bina, Yuan Kaijun, Zhang Donghui, Yang Xueming
State Key Laboratory of Molecular Reaction Dynamics and Dalian Coherent Light Source, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, P. R. China.
Marine Engineering College, Dalian Maritime University, Liaoning 116026, P. R. China.
Science. 2024 Feb 16;383(6684):746-750. doi: 10.1126/science.adn3357. Epub 2024 Feb 15.
Chemical reactions are generally assumed to proceed from reactants to products along the minimum energy path (MEP). However, straying from the MEP-roaming-has been recognized as an unconventional reaction mechanism and found to occur in both the ground and first excited states. Its existence in highly excited states is however not yet established. We report a dissociation channel to produce electronically excited fragments, S(D)+O(aΔ), from SO photodissociation in highly excited states. The results revealed two dissociation pathways: One proceeds through the MEP to produce vibrationally colder O(aΔ) and the other yields vibrationally hotter O(aΔ) by means of a roaming pathway involving an intramolecular O abstraction during reorientation motion. Such roaming dynamics may well be the rule rather than the exception for molecular photodissociation through highly excited states.
化学反应通常被认为是沿着最小能量路径（MEP）从反应物向产物进行的。然而，偏离MEP的漫游已被确认为一种非常规反应机制，并且在基态和第一激发态中均会发生。不过，其在高激发态中的存在尚未得到证实。我们报告了一个在高激发态下通过SO光解离产生电子激发碎片S(D)+O(aΔ)的解离通道。结果揭示了两条解离途径：一条通过MEP进行，产生振动温度较低的O(aΔ)；另一条则通过在重新取向运动过程中涉及分子内O提取的漫游途径，产生振动温度较高的O(aΔ)。对于通过高激发态进行的分子光解离而言，这种漫游动力学很可能是普遍规律而非个别现象。
