Li Chaofan, Hou Siting, Wang Zhimo, Xie Changjian
Institute of Modern Physics, Shaanxi Key Laboratory for Theoretical Physics Frontiers, Northwest University, Xi'an, Shaanxi 710127, China.
Phys Chem Chem Phys. 2023 Jul 19;25(28):18797-18807. doi: 10.1039/d3cp01311a.
The nσ*-mediated photodissociation dynamics of thioanisole is investigated quantum mechanically using a three-dimensional model based on a newly constructed diabatic potential energy matrix. The lifetimes of the low-lying S(ππ*) resonances are determined and found to accord well with available experimental data. Specifically, our theoretical results demonstrate that the photodissociation of thioanisole at the low-lying S(ππ*) levels takes place the heavy atom tunneling due to the higher S/S conical intersection and two equivalent out-of-plane saddle points appearing on the dissociation path. The isotopic effect on the lifetimes is found to be pronounced, manifesting the nature of the tunneling process. Moreover, the geometric phase effect around the S/S conical intersection is found to slightly impact the lifetimes due to the weak destructive or constructive interferences in this heavy atom tunneling, which differs significantly from the scenario in the nonadiabatic hydrogen atom tunneling. Importantly, the quantum mechanical treatment is essentially required to accurately describe the nσ*-mediated photodissociation dynamics of thioanisole owing to involving quantum tunneling and geometric phase effects near the conical intersection.
利用基于新构建的非绝热势能矩阵的三维模型，对苯甲硫醚的nσ介导光解离动力学进行了量子力学研究。确定了低能S(ππ)共振态的寿命，并发现其与现有实验数据吻合良好。具体而言，我们的理论结果表明，由于较高的S/S锥形交叉点以及解离路径上出现的两个等效的面外鞍点，苯甲硫醚在低能S(ππ*)能级的光解离是通过重原子隧穿发生的。发现同位素对寿命的影响很显著，这体现了隧穿过程的性质。此外，由于在这种重原子隧穿中存在微弱的相消或相长干涉，S/S锥形交叉点周围的几何相位效应被发现对寿命有轻微影响，这与非绝热氢原子隧穿的情况有显著不同。重要的是，由于涉及锥形交叉点附近的量子隧穿和几何相位效应，本质上需要采用量子力学处理方法来准确描述苯甲硫醚的nσ*介导光解离动力学。
