On the role of coherence in the transition from kinetics to dynamics: Theory and application to femtosecond unimolecular reactions
On the role of coherence in the transition from kinetics to dynamics: Theory and application to femtosecond unimolecular reactions
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关于相干性在从动力学到动力学的转变中的作用：飞秒单分子反应的理论与应用
DOI：
10.1063/1.1323729
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发表时间：
2000
影响因子：
4.4
通讯作者：
A. Zewail
中科院分区：
文献类型：
--
作者：
K. B. Møller;N. Henriksen;A. Zewail
我们考虑了在飞秒范围内观察到的泵浦探测信号与单分子反应动力学之间的关系，即反应物的指数衰减和生成物族的指数上升。结果表明，由于泵浦激光带宽内准束缚振动态之间的干涉效应不能被忽略，因此在过去通常使用的单分子衰变的标准方法中不能完全解释信号。当这些影响包括在内时，信号的所有特征都可以被解释。我们应用相干干涉的这种理论处理来研究准束缚跃迁构型的动力学和动力学，并将它们与单个准束缚共振态的衰减率联系起来。信号表现为多指数行为，反映了共振态的不同衰减速率，并具有可直接从信号中提取的平均速率常数（在泵浦激光器带宽内）。相干的持久性在观测到的信号中是明显的。以NaI的预解为原型进行数值说明。
We consider the relation between observed pump–probe signals in the femtosecond regime and the kinetics of unimolecular reactions, that is, the exponential decay of reactants and the exponential rise of the product population, respectively. It is shown that the signals cannot be fully accounted for within standard approaches of unimolecular decay, conventionally used in the past, since interference effects between the quasi-bound vibrational states within the bandwidth of the pump laser cannot be neglected. When these effects are included, all features of the signals can be accounted for. We apply this theoretical treatment of coherent interference to examine the dynamics and kinetics of the quasi-bound transition configurations, and relate them to the decay rates of individual quasi-bound resonance states. The signals show multi-exponential behavior, reflecting the different decay rates of the resonance states, with an average rate constant (within the bandwidth of the pump laser) which can be extracted directly from the signals. The persistence of coherence is evident in the observed signals. The predissociation of NaI is used as a prototype for numerical illustration.