The Institute of Mathematical Sciences, CIT Campus, Taramani, Chennai 600113, India.
J Chem Phys. 2011 Nov 28;135(20):204503. doi: 10.1063/1.3662095.
The linearized semiclassical initial value representation is employed to describe ultrafast electron transfer processes coupled to a phonon bath and weakly coupled to a proton mode. The goal of our theoretical investigation is to understand the influence of the proton on the electronic dynamics in various bath relaxation regimes. More specifically, we study the impact of the proton on coherences and analyze if the coupling to the proton is revealed in the form of an isotope effect. This will be important in distinguishing reactions in which the proton does not undergo significant rearrangement from those in which the electron transfer is accompanied by proton transfer. Unlike other methodologies widely employed to describe nonadiabatic electron transfer, this approach treats the electronic and nuclear degrees of freedom consistently. However, due to the linearized approximation, quantum interference effects are not captured accurately. Our study shows that at small phonon bath reorganization energies, coherent oscillations and isotope effect are observed in both slow and fast bath regimes. The coherences are more substantially damped by deuterium in comparison to the proton. Further, in contrast to the dynamics of the spin-boson model, the coherences are not long-lived. At large bath reorganization energies, the decay is incoherent in the slow and fast bath regimes. In this case, the extent of the isotope effect depends on the relative relaxation timescales of the proton mode and the phonon bath. The isotope effect is magnified for baths that relax on picosecond timescales in contrast to baths that relax in femtoseconds.
采用线性化半经典初值表示法来描述与声子浴耦合并与质子模式弱耦合的超快电子转移过程。我们的理论研究目的是了解质子对不同浴弛豫状态下电子动力学的影响。更具体地说，我们研究了质子对相干性的影响，并分析了质子耦合是否以同位素效应的形式表现出来。这对于区分质子没有经历显著重排的反应和电子转移伴随着质子转移的反应将非常重要。与广泛用于描述非绝热电子转移的其他方法不同，这种方法一致地处理电子和核自由度。然而，由于线性化近似，量子干涉效应不能被准确捕捉。我们的研究表明，在小的声子浴重排能量下，在慢浴和快浴两种情况下都观察到相干振荡和同位素效应。与质子相比，氘更能显著地阻尼相干性。此外，与自旋玻色子模型的动力学不同，相干性不会持久存在。在大的浴重排能量下，慢浴和快浴两种情况下的衰减都是非相干的。在这种情况下，同位素效应的程度取决于质子模式和声子浴的相对弛豫时间尺度。与弛豫在飞秒内的浴相比，在皮秒时间尺度上弛豫的浴中，同位素效应会被放大。
