X+CH4反应中反应物分子转动效应的量子动力学研究

The processing of chemical reaction should fulfill both energy requirement and geometry requirement. Two main factors of the energy requirement are structure and barrier height of the transition state and have been described by Polanyi rules. The geometry requirement is related to the anisotropy of potential energy surface and the rotational motion of reactants and has been few studied. Recently Kopin Liu’s group developed the new technique to prepare a specific rotational state of CH4 and discovered the rotational mode specificity in the Cl/O/F+CHD3 and Cl+CH4 reactions. Based on these experimental advances, we will develop the eight-dimensional and ten-dimensional quantum dynamics method with close-coupling treatment for the rotational effects. With these methods, we will study the rotational effects in X+CH4 reaction: (1) investigating the interaction of rotational modes and vibrational modes in Cl+CHD3 reactions;(2) investigating the relationship between the rotational mode specificity and the anisotropy of potential energy surface in O(3P)/F+CHD3 reactions, and inspecting the concept “vibrational-induced steric effects” suggested by Kopin Liu; (3) focusing on the vibration-rotation coupling and its effect on the specificity of Cl+CH4 reaction. We will summarize the interaction between the rotational mode and the vibrational mode, the geometry of transition state and the long-range anisotropy of potential energy surface in chemical reactions, which would shape up the understanding of reactions dynamics.

化学反应的进行需要满足一定的能量条件和几何条件。能量条件的两个主要因素是过渡态结构和能垒大小，其规律性由Polanyi规则阐明。几何条件与势能面各向异性、反应分子转动等因素有关，目前实验和理论研究较少。最近刘国平等发展了制备CH4分子转动态的实验新技术，并观察到Cl/O/F+CHD3和Cl+CH4反应中的转动模式特异性，推进了该领域的研究。本项目将针对这些实验进展，发展X+CH4反应的8维和10维量子动力学密耦理论方法，对这类反应中转动效应开展研究：(1)检验Cl+CHD3反应中各振动模式和转动模式的相互作用；(2) 考察O(3P)/F+CHD3反应势能面各向异性与转动模式的关系，检验“振动诱导立体效应”的思想；(3)分析Cl+CH4反应中CH4分子振转耦合效应。本项目将总结多原子反应中转动模式与振动模式、过渡态结构和势能面各向异性等多种因素相互作用的规律性，促进对化学反应动力学的认识。

本项目主要目的是发展新的量子动力学方法并应用于研究多原子反应中模式选择性。本项目完成的工作包括：.1.采用7维量子动力学模型研究O+CHD3反应的转动模式选择性，转动量子数于反应性的关系(Chin. J. Chem. Phys. 32, 46 (2019))；.2.发展10维量子动力学模型和软件，为研究X+CH4反应的同位素效用提供了一种可行手段。该方法被应用与研究H+CH4和H+CH3D反应，发现了H+CH3D中存在费米共振效应（J. Chem. Phys. 153, 224119 (2020)）。.3.对H+NH3反应中对称和反对称伸缩振动激发的反应性进行了详细研究，为多原子反应量子动力学计算简并态提供了依据（J. Phys. Chem. A,2022,126,663(2022)）。.4.发展了预测燃烧反应中烷烃相关反应速率常数的机器学习方案，提供获得反应速率常数的一种高效方法（Journal of Chemical Information and Modeling,61(9),4259(2021)）。