Lin Shi Ying, Guo Hua
Department of Chemistry, University of New Mexico, Albuquerque, New Mexico 87131, USA.
J Phys Chem A. 2006 Apr 27;110(16):5305-11. doi: 10.1021/jp0556299.
Using a wave packet based statistical model, we compute cross sections and thermal rate constants for various isotopic variants of the O + O2 exchange reaction on a recently modified ab initio potential energy surface. The calculation predicts a highly excited rotational distribution and relatively cold vibrational distribution for the diatomic product. A small but important threshold effect was identified for the (16)O + 18O2 reaction, which is suggested to contribute to the experimentally observed negative temperature dependence of the rate ratio, k(18O + 16O2)/k(16O + 18O2). Despite reasonable agreement with quasiclassical trajectory results, however, the calculated thermal rate constants are smaller than experimental measurements by a factor from 2 to 5. The experimentally observed negative temperature dependence of the rate constants is not reproduced. Possible reasons for the theory-experiment discrepancies are discussed.
利用基于波包的统计模型，我们在最近修正的从头算势能面上计算了O + O2交换反应各种同位素变体的截面和热速率常数。计算预测双原子产物具有高度激发的转动分布和相对较冷的振动分布。对于(16)O + 18O2反应，发现了一个小但重要的阈值效应，这被认为是导致实验观察到的速率比k(18O + 16O2)/k(16O + 18O2)负温度依赖性的原因。然而，尽管与准经典轨迹结果有合理的一致性，但计算得到的热速率常数比实验测量值小2至5倍。实验观察到的速率常数的负温度依赖性没有被再现。讨论了理论与实验差异的可能原因。
