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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Multidimensional Effects in Nonadiabatic Statistical Theories of Spin-Forbidden Kinetics: A Case Study of O-3 + CO - CO2
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Multidimensional Effects in Nonadiabatic Statistical Theories of Spin-Forbidden Kinetics: A Case Study of O-3 + CO - CO2

机译：自旋禁忌动力学非绝热统计理论中的多维效应：以O-3 + CO-> CO2为例

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摘要

The appropriateness of treating crossing seams of electronic states of different spins as nonadiabatic transition states in statistical Calculations of spin-forbidden reaction rates is considered. We show that the spin-forbidden reaction coordinate, the nuclear coordinate perpendicular to the crossing seam, is coupled to the remaining nuclear degrees of freedom. This coupling gives rise to multidimensional effects that are not typically included in statistical treatments of spin-forbidden kinetics. Three qualitative categories of multidimensional effects may be identified: static multidimensional effects due to the geometry-dependence of the local shape of the crossing seam and of the spin-orbit coupling, dynamical multidimensional effects due to energy exchange with the reaction coordinate during the seam crossing, and nonlocal (history-dependent) multidimensional effects due to interference of the electronic variables at second, third, and later seam crossings. Nonlocal multidimensional effects are intimately related to electronic decoherence, where electronic dephasing acts to erase the history of the system. A semiclassical model based on short-time full-dimensional trajectories that includes all three multidimensional effects as well as a model for electronic decoherence is presented. The results of this multidimensional nonadiabatic statistical theory (MNST) for the O-3 + CO -> CO2 reaction are compared with the results of statistical theories employing one-dimensional (Landau-Zener and weak coupling) models for the transition probability and with those calculated previously using multistate trajectories. The MNST method is shown to accurately reproduce the multistate decay-of-mixing trajectory results, so long as consistent thresholds are used. The MNST approach has several advantages over multistate trajectory approaches and is more suitable in chemical kinetics calculations at low temperatures and for complex systems. The error in statistical calculations that neglect multidimensional effects is shown to be as large as a factor of 2 for this system, with static multidimensional effects identified as the largest source of error.
机译：在自旋禁止反应速率的统计计算中，考虑将不同自旋的电子状态的交叉接缝视为非绝热过渡态的适当性。我们表明，自旋禁止反应坐标（垂直于交叉接缝的核坐标）与剩余的核自由度耦合。这种耦合产生了多维效应，通常不包括在自旋动力学的统计学处理中。可以确定多维影响的三个定性类别：由于交叉接缝的局部形状和自旋轨道耦合的几何关系而产生的静态多维影响;由于在接缝交叉时与反应坐标进行能量交换而产生的动态多维影响，以及由于第二，第三和以后的接缝处电子变量的干扰而产生的非局部（取决于历史）多维影响。非局部多维效应与电子退相干密切相关，其中电子移相的作用是消除系统的历史记录。提出了一种基于短时全尺寸轨迹的半经典模型，该模型包括所有三个多维效果以及电子退相干模型。将该O-3 + CO-> CO2反应的多维非绝热统计理论（MNST）的结果与采用一维（Landau-Zener和弱耦合）模型作为转移概率的统计理论的结果进行比较，并与先前使用多状态轨迹计算得出。只要使用一致的阈值，就可以证明MNST方法可以准确地再现多态混合衰减轨迹结果。 MNST方法具有比多状态轨迹方法更多的优势，并且更适用于低温和复杂系统的化学动力学计算。对于该系统，忽略多维影响的统计计算误差显示为2倍之大，静态多维影响被确定为最大误差源。

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