Kim Junggil, Woo Kyung Chul, Kim Sang Kyu
Department of Chemistry, KAIST, Daejeon 34141, Republic of Korea.
J Chem Phys. 2023 Mar 14;158(10):104301. doi: 10.1063/5.0143655.
Mode-dependent H atom tunneling dynamics of the O-H bond predissociation of the S phenol has been theoretically analyzed. As the tunneling is governed by the complicated multi-dimensional potential energy surfaces that are dynamically shaped by the upper-lying S(ππ*)/S(πσ*) conical intersection, the mode-specific tunneling dynamics of phenol (S) has been quite formidable to be understood. Herein, we have examined the topography of the potential energy surface along the particular S vibrational mode of interest at the nuclear configurations of the S minimum and S/S conical intersection. The effective adiabatic tunneling barrier experienced by the reactive flux at the particular S vibrational mode excitation is then uniquely determined by the topographic shape of the potential energy surface extended along the conical intersection seam coordinate associated with the particular vibrational mode. The resultant multi-dimensional coupling of the specific vibrational mode to the tunneling coordinate is then reflected in the mode-dependent tunneling rate as well as nonadiabatic transition probability. Remarkably, the mode-specific experimental result of the S phenol tunneling reaction [K. C. Woo and S. K. Kim, J. Phys. Chem. A 123, 1529-1537 (2019)] (in terms of the qualitative and relative mode-dependent dynamic behavior) could be well rationalized by semi-classical calculations based on the mode-specific topography of the effective tunneling barrier, providing the clear conceptual insight that the skewed potential energy surfaces along the conical intersection seam (strongly or weakly coupled to the tunneling reaction coordinate) may dictate the tunneling dynamics in the proximity of the conical intersection.
已对S态苯酚O-H键预解离的模式依赖型氢原子隧穿动力学进行了理论分析。由于隧穿受由上覆S(ππ*)/S(πσ*)锥形交叉点动态塑造的复杂多维势能面控制，苯酚(S)的模式特异性隧穿动力学一直难以理解。在此，我们研究了在S态最小值和S/S态锥形交叉点的核构型下，沿着感兴趣的特定S态振动模式的势能面形貌。然后，在特定S态振动模式激发下，反应通量所经历的有效绝热隧穿势垒由沿着与特定振动模式相关的锥形交叉点接缝坐标延伸的势能面的形貌唯一确定。特定振动模式与隧穿坐标的多维耦合结果随后反映在模式依赖型隧穿速率以及非绝热跃迁概率中。值得注意的是，S态苯酚隧穿反应的模式特异性实验结果[K. C. Woo和S. K. Kim，《物理化学杂志A》123, 1529 - 1537 (2019)]（就定性和相对模式依赖型动力学行为而言）可以通过基于有效隧穿势垒的模式特异性形貌的半经典计算得到很好的解释，这提供了清晰的概念性见解，即沿着锥形交叉点接缝的倾斜势能面（与隧穿反应坐标强耦合或弱耦合）可能决定锥形交叉点附近的隧穿动力学。
