Department of Chemistry, University of Illinois, Urbana, Illinois 61801, United States.
Department of Physics, University of Illinois, Urbana, Illinois 61801, United States.
J Phys Chem B. 2020 Jun 18;124(24):5028-5038. doi: 10.1021/acs.jpcb.0c03032. Epub 2020 Jun 4.
We use the quantum-classical path integral (QCPI) methodology to report numerically exact, fully quantum mechanical results for the exciton-vibration dynamics in the bacteriochlorophyll dimer, including all 50 coupled vibrational normal modes of each bacteriochlorophyll explicitly with parameters obtained from spectroscopic Huang-Rhys factors. We present a coordinate transformation that maps the dimer on a spin-Boson Hamiltonian with a single collective bath. We consider two vibrational initial conditions which correspond to a Franck-Condon excitation or to modes initially equilibrated with the excited monomer. Our calculations reveal persistent, underdamped oscillations of the electronic energy between the two pigments at room temperature. Static disorder leads to additional damping, but the population dynamics remains oscillatory. The population curves exhibit atypical, nonsmooth features that arise from the complexity of the bacteriochlorophyll vibrational spectrum and which cannot be captured by simple analytical spectral density functions.
我们使用量子经典路径积分 (QCPI) 方法，对细菌叶绿素二聚体中的激子-振动动力学进行数值精确的全量子力学研究，包括每个细菌叶绿素的 50 个耦合振动正则模式，所有参数均来自光谱 Huang-Rhys 因子。我们提出了一种坐标变换，将二聚体映射到具有单个集体浴的自旋玻色子哈密顿量上。我们考虑两种振动初始条件，分别对应于 Franck-Condon 激发或与激发单体初始平衡的模式。我们的计算揭示了室温下两个颜料之间电子能量的持续、欠阻尼振荡。静态无序会导致额外的阻尼，但种群动力学仍然是振荡的。种群曲线表现出非典型的非平滑特征，这是由于细菌叶绿素振动光谱的复杂性，而简单的分析光谱密度函数无法捕捉到这些特征。
