Belyaev Andrey K, Domcke Wolfgang, Lasser Caroline, Trigila Giulio
Department of Theoretical Physics, Herzen University, St. Petersburg 191186, Russia.
Department Chemie, Technische Universität München, D-85747 Garching, Germany.
J Chem Phys. 2015 Mar 14;142(10):104307. doi: 10.1063/1.4913962.
The Landau-Zener (LZ) type classical-trajectory surface-hopping algorithm is applied to the nonadiabatic nuclear dynamics of the ammonia cation after photoionization of the ground-state neutral molecule to the excited states of the cation. The algorithm employs a recently proposed formula for nonadiabatic LZ transition probabilities derived from the adiabatic potential energy surfaces. The evolution of the populations of the ground state and the two lowest excited adiabatic states is calculated up to 200 fs. The results agree well with quantum simulations available for the first 100 fs based on the same potential energy surfaces. Three different time scales are detected for the nuclear dynamics: Ultrafast Jahn-Teller dynamics between the excited states on a 5 fs time scale; fast transitions between the excited state and the ground state within a time scale of 20 fs; and relatively slow partial conversion of a first-excited-state population to the ground state within a time scale of 100 fs. Beyond 100 fs, the adiabatic electronic populations are nearly constant due to a dynamic equilibrium between the three states. The ultrafast nonradiative decay of the excited-state populations provides a qualitative explanation of the experimental evidence that the ammonia cation is nonfluorescent.
将朗道-齐纳（LZ）型经典轨迹表面跳跃算法应用于基态中性分子光离子化至阳离子激发态后氨阳离子的非绝热核动力学。该算法采用了最近从绝热势能面导出的非绝热LZ跃迁概率公式。计算了基态和两个最低激发绝热态的布居数演化，时间长达200飞秒。结果与基于相同势能面的前100飞秒的量子模拟结果吻合良好。核动力学检测到三种不同的时间尺度：激发态之间在5飞秒时间尺度上的超快 Jahn-Teller 动力学；激发态与基态之间在20飞秒时间尺度内的快速跃迁；以及在100飞秒时间尺度内第一激发态布居数向基态的相对缓慢的部分转化。超过100飞秒后，由于三个态之间的动态平衡，绝热电子布居数几乎恒定。激发态布居数的超快非辐射衰变对氨阳离子无荧光的实验证据提供了定性解释。
