Department of Chemistry, Gangneung-Wonju National University, Gangneung, Gangwondo, Korea.
J Phys Chem A. 2011 Nov 24;115(46):13309-15. doi: 10.1021/jp208117p. Epub 2011 Oct 20.
An earlier time-dependent quantum wave packet propagation study of the photochemistry of Ph-OH [J. Chem. Phys. 2005, 122, 224315] is extended to investigate isotope effects (for Ph-OD) and the dynamics initiated by direct (vibronically induced) excitation to the (1)πσ* state. The isotope effect is significant only when the initially excited state is (1)ππ*, that is, there are noticeable changes not only in the time scale but also in the branching ratio (Ã/X̃) for the electronic states of the product Ph-O radical. In contrast, the isotope effect on the dynamics initiated by direct excitation to the (1)πσ* state is very small. Our most important observation for the dynamics initiated by direct excitation to the (1)πσ* state is that the initial excitation of the O-H stretch mode does not result in a noticeable enhancement of the product Ph-O radical in the à state, which corresponds to a dissociating H atom with low kinetic energy. The initial excitation of the CCOH torsion mode is the main reason for the enhancement of the product Ph-O radical in the à state that was observed in a vibrationally mediated two-photon experiment [J. Chem. Phys.2008, 128, 104307].
早期的 Ph-OH 光化学反应的时变量子波包传播研究[J. Chem. Phys. 2005, 122, 224315]被扩展到研究同位素效应（对于 Ph-OD）和直接（通过振子诱导）激发到（1）πσ态引发的动力学。只有当最初激发的态是（1）ππ时，同位素效应才显著，即不仅在时间尺度上，而且在产物 Ph-O 自由基的电子态的分支比（Ã/X̃）上都有明显的变化。相比之下，直接激发到（1）πσ态引发的动力学的同位素效应非常小。对于直接激发到（1）πσ态引发的动力学，我们最重要的观察结果是，O-H 伸缩模式的初始激发不会导致产物 Ph-O 自由基在Ã态中明显增强，这对应于具有低动能的解离 H 原子。初始激发 CCOH 扭转模式是在振动介导的双光子实验[J. Chem. Phys.2008, 128, 104307]中观察到的Ã态产物 Ph-O 自由基增强的主要原因。
