Abe Mayumi, Ohtsuki Yukiyoshi, Fujimura Yuichi, Lan Zhenggang, Domcke Wolfgang
Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan.
J Chem Phys. 2006 Jun 14;124(22):224316. doi: 10.1063/1.2203611.
Optimal control simulation is used to examine the control mechanisms in the photodissociation of phenol within a two-dimensional, three-electronic-state model with two conical intersections. This model has two channels for H-atom elimination, which correspond to the (2)pi and (2)sigma states of the phenoxyl radical. The optimal pulse that enhances (2)sigma dissociation initially generates a wave packet on the S(1) potential-energy surface of phenol. This wave packet is bifurcated at the S(2)-S(1) conical intersection into two components with opposite phases because of the geometric phase effect. The destructive interference caused by the geometric phase effect reduces the population around the S(1)-S(0) conical intersection, which in turn suppresses nonadiabatic transitions and thus enhances dissociation to the (2)sigma limit. The optimal pulse that enhances S(0) dissociation, on the other hand, creates a wave packet on the S(2) potential-energy surface of phenol via an intensity borrowing mechanism, thus avoiding geometric phase effects at the S(2)-S(1) conical intersection. This wave packet hits the S(1)-S(0) conical intersection directly, resulting in preferred dissociation to the (2)pi limit. The optimal pulse that initially prepares the wave packet on the S(1) potential-energy surface (PES) has a higher carrier frequency than the pulse that prepares the wave packet on the S(2) PES. This counterintuitive effect is explained by the energy-level structure and the S(2)-S(1) vibronic coupling mechanism.
最优控制模拟用于研究在具有两个锥形交叉点的二维三电子态模型中苯酚光解离的控制机制。该模型有两个氢原子消除通道，分别对应苯氧基自由基的(2)π和(2)σ态。增强(2)σ解离的最优脉冲最初在苯酚的S(1)势能面上产生一个波包。由于几何相位效应，这个波包在S(2)-S(1)锥形交叉点处分裂为两个相位相反的分量。几何相位效应引起的相消干涉减少了S(1)-S(0)锥形交叉点周围的布居数，进而抑制了非绝热跃迁，从而增强了向(2)σ极限的解离。另一方面，增强S(0)解离的最优脉冲通过强度借用机制在苯酚的S(2)势能面上创建一个波包，从而避免了在S(2)-S(1)锥形交叉点处的几何相位效应。这个波包直接撞击S(1)-S(0)锥形交叉点，导致优先解离到(2)π极限。最初在S(1)势能面（PES）上制备波包的最优脉冲比在S(2) PES上制备波包的脉冲具有更高的载波频率。这种违反直觉的效应通过能级结构和S(2)-S(1)电子振动耦合机制来解释。
