Holdaway David I H, Collini Elisabetta, Olaya-Castro Alexandra
Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom.
Department of Chemical Sciences, University of Padova, I-35131 Padova, Italy.
J Chem Phys. 2016 May 21;144(19):194112. doi: 10.1063/1.4948943.
We examine transient circular dichroism (TRCD) spectroscopy as a technique to investigate signatures of exciton coherence dynamics under the influence of structured vibrational environments. We consider a pump-probe configuration with a linearly polarized pump and a circularly polarized probe, with a variable angle θ between the two directions of propagation. In our theoretical formalism the signal is decomposed in chiral and achiral doorway and window functions. Using this formalism, we show that the chiral doorway component, which beats during the population time, can be isolated by comparing signals with different values of θ. As in the majority of time-resolved pump-probe spectroscopy, the overall TRCD response shows signatures of both excited and ground state dynamics. However, we demonstrate that the chiral doorway function has only a weak ground state contribution, which can generally be neglected if an impulsive pump pulse is used. These findings suggest that the pump-probe configuration of optical TRCD in the impulsive limit has the potential to unambiguously probe quantum coherence beating in the excited state. We present numerical results for theoretical signals in an example dimer system.
我们研究瞬态圆二色性（TRCD）光谱技术，以探究在结构化振动环境影响下激子相干动力学的特征。我们考虑一种泵浦 - 探测配置，其中泵浦光为线偏振光，探测光为圆偏振光，两者传播方向之间的夹角为可变角度θ。在我们的理论形式中，信号被分解为手性和非手性的门道函数与窗口函数。使用这种形式，我们表明，在布居时间内产生拍频的手性门道分量，可以通过比较不同θ值下的信号来分离。与大多数时间分辨泵浦 - 探测光谱一样，整体TRCD响应显示出激发态和基态动力学的特征。然而，我们证明手性门道函数对基态的贡献很小，如果使用脉冲泵浦脉冲，通常可以忽略不计。这些发现表明，在脉冲极限下光学TRCD的泵浦 - 探测配置有潜力明确探测激发态中的量子相干拍频。我们给出了一个示例二聚体系统中理论信号的数值结果。
