Fu Yan-Lin, Lu Xiaoxiao, Han Yong-Chang, Fu Bina, Zhang Dong H, Bowman Joel M
Department of Physics, Dalian University of Technology Dalian China 116024
State Key Laboratory of Molecular Reaction Dynamics, Center for Theoretical and Computational Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences Dalian China 116023
Chem Sci. 2020 Jan 10;11(8):2148-2154. doi: 10.1039/c9sc05951b.
Roaming is a novel mechanism in reaction dynamics. It describes an unusual pathway, which can be quite different from the conventional minimum-energy path, leading to products. While roaming has been reported or suggested in a number of unimolecular reactions, it has been rarely reported for bimolecular reactions. Here, we report a high-level computational study of roaming dynamics in the important bimolecular combustion reaction H + CH → H + CH, using a new, high-level machine learning-based potential energy surface. In addition to the complex-mediated roaming mechanism, a non-complex forming roaming mechanism is found. It can be described as a direct inelastic collision where the departing H atom roams and then abstracts an H atom. We denoted this as "collision-induced" roaming. These two roaming mechanisms have different angular distributions; however, both produce highly internally excited CH. The roaming pathway leads to remarkably different dynamics as compared with the direct abstraction pathway. A clear signature of the roaming mechanism is highly internally excited CH, which could be observed experimentally.
漫游是反应动力学中的一种新机制。它描述了一条不寻常的路径，该路径可能与传统的最小能量路径大不相同，最终生成产物。虽然在许多单分子反应中已报道或提出了漫游现象，但在双分子反应中却鲜有报道。在此，我们使用一种基于机器学习的新型高水平势能面，对重要的双分子燃烧反应H + CH → H + CH中的漫游动力学进行了高水平的计算研究。除了复杂介导的漫游机制外，还发现了一种非复杂形成的漫游机制。它可以被描述为一种直接的非弹性碰撞，其中离去的H原子进行漫游，然后夺取一个H原子。我们将此称为“碰撞诱导”漫游。这两种漫游机制具有不同的角分布；然而，两者都会产生高度内部激发的CH。与直接夺取路径相比，漫游路径导致了显著不同的动力学。漫游机制的一个明显特征是高度内部激发的CH，这可以通过实验观察到。
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