The reaction of OH radicals with HBr plays a key role in atmospheric chemistry as the reaction, OH + HBr → Br + H₂O, produces Br atoms that destroy ozone. The experimental measurements of the kinetic isotope effect of k(OH + HBr)/k(OH + DBr) found that the kinetic isotope effects are temperature-independent. However, previous quasi-classical trajectory calculations on an accurate ab initio potential energy surface showed that the kinetic isotope effect is temperature-dependent. By contrast, the present full-dimensional time-dependent quantum dynamics calculations on the same potential energy surface find that the kinetic isotope effect is temperature-independent, agreeing well with the experimental studies both qualitatively and quantitatively. Furthermore, the rate constants from both quantum dynamics and quasi-classical trajectory calculations have a peak at around 15 K whereas the experimental data are not available in this low temperature range. The good agreement of the temperature-dependence of kinetic isotope effects between the present quantum dynamics calculations and the experimental measurements indicates that the kinetic isotope effect of k(OH + HBr)/k(OH + DBr) should be temperature-independent and the peak of the rate constants from the theoretical calculations call for experimental measurements at a very low temperature range.

中文翻译：

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量子动力学计算揭示了OH + HBr / DBr反应的动力学同位素效应的温度独立性

OH自由基与HBr的反应在大气化学中起关键作用，因为该反应OH + HBr→Br + H ₂ O产生破坏臭氧的Br原子。k（OH + HBr）/ k（OH + DBr）的动力学同位素效应的实验测量发现，动力学同位素效应与温度无关。但是，先前关于精确从头算起的准经典轨迹计算势能面表明，动力学同位素效应与温度有关。相比之下，目前在同一势能表面上的全时空量子动力学计算结果发现，动力学同位素效应与温度无关，在定性和定量方面都与实验研究相吻合。此外，来自量子动力学和准经典轨迹计算的速率常数在15 K左右有一个峰值，而在此低温范围内没有实验数据。当前的量子动力学计算与实验测量结果之间的动力学同位素效应的温度依赖性的良好一致性表明，k（OH + HBr）/ k的动力学同位素效应（OH + DBr）应该与温度无关，并且理论计算得出的速率常数的峰值要求在非常低的温度范围内进行实验测量。