We report a detailed dynamics study on the mode-specificity of the Cl + C₂H₆ → HCl + C₂H₅ 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.

中文翻译：

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Cl + C2H6→ HCl + C2H5 反应动力学中的振动模式特异性

我们报告了关于 Cl + C ₂ H ₆ → HCl + C ₂ H ₅ H 抽象反应的模式特异性的详细动力学研究。我们使用最近开发的高级ab initio执行准经典轨迹模拟通过在四种碰撞能量下激发乙烷的五种不同振动模式来获得全维势能表面。我们发现，除了 CC 拉伸模式之外，所有研究的振动激发都明显促进了标题反应，并且振动增强与突然矢量投影（SVP）模型的预测一致，其中由CH-拉伸激发。还监测了不同激发的乙烷分子的分子内振动再分布。我们的结果表明，反应机制随着碰撞能量的增加而变化，在高能量下没有模式特异性。初始平移能主要转化为产物反冲，而大部分多余的振动能保留在乙基自由基中。