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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Photoionization dynamics of glycine: The first 10 picoseconds
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Photoionization dynamics of glycine: The first 10 picoseconds

机译：甘氨酸的光电离动力学：前10皮秒

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Single photon ionization dynamics of glycine is studied by classical trajectory simulations using the semiempirical PM3 potential surface in "on the fly" calculations. The glycine conformer is assumed to be in the vibrational ground state prior to ionization. Initial conditions for the trajectories are weighted according to the Wigner distribution function computed for that state. Vertical ionization in the spirit of the classical Franck-Condon principle is assumed. The main findings are as follows: (1) The photoionization triggers a fast internal rotation about the C-C bond, with the NH2 group rotating in one direction, and the COOH group rotating in the opposite direction. For the trajectories where the fast rotation occurs, it persists till the end of the simulation (10 ps). The yield for this process is about 6%, suggesting it may be experimentally observable. (2) For many of the trajectories, the photoproduced glycine ion exhibits "hops" between two conformer structures. The rates computed from the dynamics for these conformational transitions differ considerably from RRK predictions. (3) Different behavior of vibrational energy flow is found for different types of modes. There is no significant approach to statistical distribution of the energy throughout the first 10 picoseconds. (4) The preferred dissociation channel is the C-C bond cleavage. Indeed, fragmentation is observed for a few trajectories, one of them shows H atom hopping from the amino group to the carbonyl group prior to dissociation. Another trajectory shows only this hydrogen transfer and the transfer back. Possible experimental implications of some of the findings are briefly discussed.
机译：在“运行中”计算中，使用半经验PM3势面，通过经典轨迹模拟研究了甘氨酸的单光子电离动力学。假定甘氨酸构象体在电离之前处于振动基态。根据为该状态计算的维格纳分布函数，对轨迹的初始条件进行加权。假定按照经典弗兰克-康登原理的精神进行垂直电离。主要发现如下：（1）光电离引发围绕C-C键的快速内部旋转，其中NH2基团沿一个方向旋转，而COOH基团沿相反方向旋转。对于发生快速旋转的轨迹，它一直持续到模拟结束（10 ps）。此过程的收率约为6％，表明它在实验上可以观察到。 （2）对于许多轨迹，光产生的甘氨酸离子在两个构象结构之间表现出“跳跃”。从动力学上计算出的这些构象转变的速率与RRK预测相差很大。 （3）对于不同类型的模式，发现了振动能流的不同行为。在最初的10皮秒内没有统计能量分布的有效方法。 （4）优选的解离通道是C-C键裂解。实际上，在一些轨迹上观察到了断裂，其中之一显示了在离解之前，H原子从氨基跳到羰基。另一个轨迹仅显示了氢的转移和向后转移。简要讨论了一些发现的可能的实验含义。

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