Abstract：
Ultrafast spectroscopic techniques have been vital in studying excitation energy transfer (EET) in photosynthetic light harvesting complexes. In this paper, we simulate the pump-probe spectra of the B850 band of the light harvesting complex 2 (LH2) of purple bacteria, by using the hierarchical equation of motion method and the optical response function approach. The ground state bleach, stimulated emission, and excited state absorption components of the pump-probe spectra are analyzed in detail. The laser pulse-induced population dynamics are also simulated to help understand the main features of the pump-probe spectra and the EET process. It is shown that the excitation energy relaxation is an ultrafast process with multiple time scales. The first 40 fs of the pump-probe spectra is dominated by the relaxation of the k = ±1 states to both the k = 0 and higher energy states. Dynamics on a longer time scale around 200 fs reflects the relaxation of higher energy states to the k = 0 state.
摘要：
超快光谱技术对于研究光合集光复合物中的激发能量转移（EET）至关重要。在本文中,我们模拟了紫色细菌的光捕获复合物2（LH2）的B850波段的泵浦-探针光谱，运动方程法和光学响应函数法。基态漂白剂,受激发射,详细分析了泵浦-探针光谱的激发态吸收成分。还模拟了激光脉冲诱导的种群动力学，以帮助了解泵浦探针光谱和EET过程的主要特征。表明，激发能量弛豫是具有多个时间尺度的超快过程。泵浦探测光谱的前40fs由k=±1状态到k=0和更高能量状态的弛豫所主导。在200fs左右的较长时间尺度上的动力学反映了较高能量状态到k=0状态的弛豫。
