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 Lett. 2020 Oct 15;11(20):8783-8789. doi: 10.1021/acs.jpclett.0c02760. Epub 2020 Oct 1.
The mechanism of excitation energy transfer in photoexcited bacteriochlorophyll (BChl) aggregates poses intriguing questions, which have important implications for the observed efficiency of photosynthesis. We investigate this process through fully quantum mechanical calculations of exciton-vibration dynamics in chains and rings of BChl molecules, with parameters characterizing the B850 ring of the LH2 complex of photosynthetic bacteria. The calculations are performed using the modular path integral methodology, which allows the exact treatment of 50 intramolecular vibrations on each pigment using parameters obtained from spectroscopic Huang-Rhys factors with computational effort that scales linearly with aggregate length. Our results indicate that the interplay between electronic and vibrational time scales leads to the rapid suppression but not the overdamping of electronic coherence, which facilitates the spreading of excitation energy throughout the aggregate.
在光激发细菌叶绿素（BChl）聚集体中，激发能量转移的机制提出了有趣的问题，这对观察到的光合作用效率有重要影响。我们通过对细菌叶绿素分子链和环中激子-振动动力学的全量子力学计算来研究这个过程，所使用的参数描述了光合细菌 LH2 复合物的 B850 环。计算是使用模块化路径积分方法进行的，该方法允许使用从光谱 Huang-Rhys 因子获得的参数精确处理每个色素上的 50 个分子内振动，计算工作量与聚集体长度呈线性比例。我们的结果表明，电子和振动时间尺度之间的相互作用导致电子相干的快速抑制而不是过阻尼，这有利于激发能量在整个聚集体中的传播。
