MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary.
Phys Chem Chem Phys. 2023 Jan 27;25(4):3083-3091. doi: 10.1039/d2cp05334a.
A quasi-classical trajectory (QCT) study is performed for the HBr + CH multi-channel reaction using a recently-developed high-level full-dimensional spin-orbit-corrected potential energy surface (PES) by exciting five different vibrational modes of reactants at five collision energies. The effect of the normal-mode excitations on the reactivity, the mechanism, and the post-reaction energy flow is followed. A significant decrease of the reactivity caused by the longer initial distances of the reactants for the = 1 reaction at low collision energy () is observed due to the intramolecular vibrational-energy redistribution and the classical nature of the QCT method. All of the three reaction pathways (H-abstraction, Br-abstraction, and H-exchange) are intensely promoted when the HBr-stretching mode is excited. No clear promotion is observed when excitation is imposed to CH except that asymmetric CH-stretching helps the H-exchange process. The enhancement effect of the excitation in the HBr vibrational mode is found to be much more effective than increasing the translational energy, in contrast to the HBr + CH reaction. The forward scattering mechanism can be clearly promoted by the excitation of the HBr-stretching mode, or by the high collision energy, indicating the dominance of the direct stripping mechanism in these cases. At low collision energy with no excitation or excitation of any vibrational mode of CH, the forward scattering feature is less obvious. At = 1 kcal mol, when HBr-stretching is excited, the product clearly gains more relative translational energy. However, it is interesting to see that when the excitation is in CH, the effect is the opposite, , the product gains less relative translational energy compared to the ground-state reaction.
采用最新发展的高水准全维自旋轨道修正势能面（PES），通过激发反应物的五个不同振动模式在五个碰撞能下，对 HBr + CH 多通道反应进行了准经典轨线（QCT）研究。研究了各振动模式激发对反应活性、反应机理和反应后能量流动的影响。在低碰撞能（）下，由于反应物的初始距离变长，以及 QCT 方法的经典特性，导致 = 1 的反应活性显著降低，这是由于分子内振动能重新分配所致。当激发 HBr 伸缩模式时，三种反应途径（H 提取、Br 提取和 H 交换）均得到强烈促进。当激发 CH 时，除了不对称 CH 伸缩有助于 H 交换过程外，没有明显的促进作用。与 HBr + CH 反应相反，发现激发 HBr 振动模式的增强效果比增加平动能量更有效。通过激发 HBr 伸缩模式或高碰撞能，可以明显促进前向散射机制，这表明在这些情况下直接剥离机制占主导地位。在没有激发或激发 CH 的任何振动模式的低碰撞能下，前向散射特征不太明显。在 = 1 kcal mol 时，当激发 HBr 伸缩时，产物明显获得更多的相对平移能。然而，有趣的是，当激发在 CH 中时，情况则相反，产物获得的相对平移能比基态反应少。
