Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun,Beijing 100190, China.
China University of Chinese Academy of Sciences, Beijing 100049, China.
J Phys Chem B. 2024 Aug 8;128(31):7467-7475. doi: 10.1021/acs.jpcb.4c02059. Epub 2024 Jul 26.
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 = ±1 states to both the = 0 and higher energy states. Dynamics on a longer time scale around 200 fs reflects the relaxation of higher energy states to the = 0 state.
超快光谱技术在研究光合作用光捕获复合物中的激发能量转移（EET）方面发挥了重要作用。在本文中，我们使用层次运动方程方法和光响应函数方法模拟了细菌的光捕获复合物 2（LH2）的 B850 带的泵浦探测光谱。详细分析了泵浦探测光谱的基态漂白、受激辐射和激发态吸收分量。还模拟了激光脉冲诱导的种群动力学，以帮助理解泵浦探测光谱和 EET 过程的主要特征。结果表明，激发能弛豫是一个具有多个时间尺度的超快过程。泵浦探测光谱的前 40 fs 主要由 = ±1 态弛豫到 = 0 和更高能量态主导。在 200 fs 左右的较长时间尺度上的动力学反映了更高能量态向 = 0 态的弛豫。
