Mode Specificity in the OH + HO2 → H2O + O2 Reaction: Enhancement of Reactivity by Exciting a Spectator Mode
Mode Specificity in the OH + HO2 → H2O + O2 Reaction: Enhancement of Reactivity by Exciting a Spectator Mode
复制标题
OH HO2 -> H2O O2 反应中的模式特异性：通过激发观察者模式增强反应性
DOI：
10.1021/jacs.9b12467
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发表时间：
2020-02-19
影响因子：
15
通讯作者：
Guo, Hua
中科院分区：
文献类型：
--
作者：
Liu, Yang;Song, Hongwei;Guo, Hua
反应通常包括几个活动模式，而其他模式在整个反应过程中作为观众保留了很大一部分。主动模式的激发预计会促进反应，但在旁观者模式下储存能量通常没有影响，因为能量流向反应坐标的能力不同。在这项工作中，我们报告了一个令人惊讶的例子，在一个关键的自由基-自由基反应OH+HO2->；H2O+O-2中，模式专一性的情况下，这种正则预期不成立。尽管它是旁观性的，但在低碰撞能下表现出OH反应物的振动激发，从而显著提高了反应活性。这种独特的效应可以归因于由于伸展的OH的更大的偶极而增加了对Ho2的吸引。在低碰撞能量下，较强的吸引力增加了捕获反应物形成氢键络合物的机会，从而通过淹没的势垒。这种新的机制不同于传统的通过耦合到过渡态的反应坐标来增强振动的机制，丰富了我们对化学中模式特异性的理解。
A reaction typically involves a few active modes while the other modes are largely preserved throughout the reaction as spectators. Excitation of an active mode is expected to promote the reaction, but depositing energy in a spectator mode typically has no effect, because of the differing ability for energy flow to the reaction coordinate. In this work, we report a surprising case of mode specificity in a key radical-radical reaction OH + HO2 -> H2O + O-2, where such canonical expectations fail to hold. Despite its spectator nature, the vibrational excitation of the OH reactant is shown at low collision energies to enhance the reactivity significantly. This unique effect can be attributed to the increased attraction with HO 2 due to the larger dipole of the stretched OH. At low collision energies, the stronger attraction increases the chance of capturing the reactants to form a hydrogen-bonded complex, thus of passing through the submerged barrier. The novel mechanism differs from the conventional vibrational enhancement via coupling to the reaction coordinate at the transition state, enriching our understanding of mode specificity in chemistry.