Lin Shi Ying, Guo Hua
Department of Chemistry, University of New Mexico, Albuquerque, New Mexico 87131, USA.
J Chem Phys. 2004 Jul 15;121(3):1285-92. doi: 10.1063/1.1764502.
Using a Chebyshev wave packet method, total and state-resolved reaction probabilities (J=0) were calculated for the reactions of C(1D) with various hydrogen isotopomers (H2, D2, and HD, nu i=0, j i=0) on a recent ab initio potential energy surface. For all the isotopic variants, it was found that the initial state specified reaction probabilities have no energy threshold and are strongly oscillatory, indicative of the involvement of long-lived resonances in this barrierless reaction. The J=0 product vibrational and rotational distributions for all three isotopic reactions, and the CH/CD branching ratio for the C+HD reaction, show strong dependence on the collision energy, further underscoring the important role played by the resonances. The generally decaying vibrational distributions and highly excited rotational distributions, which corroborate an insertion mechanism, and the dominance of the CD+H channel in the C+HD reaction are consistent with existing experimental observations. Initial state specified integral cross sections and rate constants were estimated using a capture model. The estimated rate constants were found to be close and in the order kHD>kH2>kD2. Finally, a method to calculate branching ratio in the C+HD reaction is proposed.
使用切比雪夫波包方法，在最近的从头算势能面上计算了C(¹D)与各种氢同位素分子（H₂、D₂和HD，νᵢ = 0，jᵢ = 0）反应的总反应概率和态分辨反应概率（J = 0）。对于所有同位素变体，发现特定初始态的反应概率没有能量阈值且强烈振荡，这表明在这个无势垒反应中存在长寿命共振。所有三种同位素反应的J = 0产物振动和转动分布，以及C + HD反应的CH/CD分支比，都强烈依赖于碰撞能量，进一步突出了共振所起的重要作用。普遍衰减的振动分布和高度激发的转动分布证实了一种插入机制，并且C + HD反应中CD + H通道的主导地位与现有的实验观察结果一致。使用捕获模型估计了特定初始态的积分截面和速率常数。发现估计的速率常数相近，顺序为kHD > kH₂ > kD₂。最后，提出了一种计算C + HD反应中分支比的方法。
