Papp Dóra, Li Jun, Guo Hua, Czakó Gábor
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.
School of Chemistry and Chemical Engineering and Chongqing Key Laboratory of Theoretical and Computational Chemistry, Chongqing University, Chongqing 401331, China.
J Chem Phys. 2021 Sep 21;155(11):114303. doi: 10.1063/5.0062677.
We report a detailed dynamics study on the mode-specificity of the Cl + CH → HCl + CH H-abstraction reaction. We perform quasi-classical trajectory simulations using a recently developed high-level ab initio full-dimensional potential energy surface by exciting five different vibrational modes of ethane at four collision energies. We find that all the studied vibrational excitations, except that of the CC-stretching mode, clearly promote the title reaction, and the vibrational enhancements are consistent with the predictions of the Sudden Vector Projection (SVP) model, with the largest effect caused by the CH-stretching excitations. Intramolecular vibrational redistribution is also monitored for the differently excited ethane molecule. Our results indicate that the mechanism of the reaction changes with increasing collision energy, with no mode-specificity at high energies. The initial translational energy mostly converts into product recoil, while a significant part of the excess vibrational energy remains in the ethyl radical. An interesting competition between translational and vibrational energies is observed for the HCl vibrational distribution: the effect of exciting the low-frequency ethane modes, having small SVP values, is suppressed by translational excitation, whereas a part of the excess vibrational energy pumped into the CH-stretching modes (larger SVP values) efficiently flows into the HCl vibration.
我们报告了一项关于Cl + CH → HCl + CH氢提取反应模式特异性的详细动力学研究。我们使用最近开发的高水平从头算全维势能面，在四个碰撞能量下激发乙烷的五种不同振动模式，进行准经典轨迹模拟。我们发现，除了CC伸缩模式外，所有研究的振动激发都明显促进了该反应，并且振动增强与突然矢量投影（SVP）模型的预测一致，其中CH伸缩激发引起的影响最大。还对不同激发态的乙烷分子监测了分子内振动再分布。我们的结果表明，反应机制随碰撞能量增加而变化，在高能量下没有模式特异性。初始平动能大多转化为产物反冲，而过量振动能的很大一部分保留在乙基自由基中。对于HCl振动分布，观察到平动能和振动能之间有趣的竞争：激发具有小SVP值的低频乙烷模式的效果被平动激发抑制，而注入到CH伸缩模式（较大SVP值）的一部分过量振动能有效地流入HCl振动。
