Two-Dimensional Master Equation Modeling of Some Multichannel Unimolecular Reactions
Two-Dimensional Master Equation Modeling of Some Multichannel Unimolecular Reactions
复制标题
一些多通道单分子反应的二维主方程建模
DOI：
10.1021/acs.jpca.1c00666
复制
发表时间：
2021
期刊：
影响因子：
2.9
通讯作者：
Akira Matsugi
中科院分区：
文献类型：
--
作者：
Takeshi Yasunaga;Yasuyuki Ikegami;Akira Matsugi
通过求解作为总能量(E)和角动量(J)的函数的二维主方程，研究了正丙基、1-戊基和甲苯的多通道热分解反应。本研究的主要目的是阐明角动量在多通道单分子反应动力学中的作用。在经典轨道计算的基础上，描述了反应物与Ar碰撞的碰撞跃迁过程，并在主方程中实现。比较了用二维主方程计算的速率常数和用一维主方程计算的速率常数。角动量的显式处理的结果取决于微观速率常数的J依赖性，并在甲苯的热分解中特别强调，其中考虑了C-H键和C-C键的裂变通道。在能量有利的C-H键裂变中，离心力效应并不显著，但在能量较高的C-C键裂变中，离心力效应是显著的，这会导致微观速率常数的旋转通道切换。对J相关的通道耦合效应、J的弱碰撞转移和初始J相关的碰撞能量转移的适当处理对于预测低压下的分支分数是必不可少的。
Multichannel thermal decomposition reactions ofn-propyl radicals, 1-pentyl radicals, and toluene are investigated by solving a two-dimensional master equation formulated as a function of total energy (E) and angular momentum (J). The primary aim of this study is to elucidate the role of angular momentum in the kinetics of multichannel unimolecular reactions. The collisional transition processes of the reactants colliding with argon are characterized based on the classical trajectory calculations and implemented in the master equation. The rate constants calculated by using the two-dimensional master equation are compared with those of one-dimensional master equations. The consequence of the explicit treatment of angular momentum depends on theJdependence of the microscopic rate constants and is particularly emphasized in the thermal decomposition of toluene, for which the C–H and C–C bond fission channels are considered. The centrifugal effect is insignificant in the energetically favored C–H bond fission but is substantial in the energetically higher C–C bond fission, which causes rotational channel switching of the microscopic rate constants. The proper treatment of theJ-dependent channel coupling effect, weak collisional transfer ofJ, and initial-J-dependent collisional energy transfer are found to be essential for predicting the branching fractions at low pressures.