Caycedo-Soler Felipe, Lim James, Oviedo-Casado Santiago, van Hulst Niek F, Huelga Susana F, Plenio Martin B
Institute of Theoretical Physics and Integrated Quantum Science and Technology IQST , University of Ulm , Albert-Einstein-Allee 11 , D-89069 Ulm , Germany.
Departmento de Física Aplicada , Universidad Politécnica de Cartagena , 30202 Cartagena , Spain.
J Phys Chem Lett. 2018 Jun 21;9(12):3446-3453. doi: 10.1021/acs.jpclett.8b00933. Epub 2018 Jun 11.
Nonlinear spectroscopy has revealed long-lasting oscillations in the optical response of a variety of photosynthetic complexes. Different theoretical models that involve the coherent coupling of electronic (excitonic) or electronic-vibrational (vibronic) degrees of freedom have been put forward to explain these observations. The ensuing debate concerning the relevance of either mechanism may have obscured their complementarity. To illustrate this balance, we quantify how the excitonic delocalization in the LH2 unit of Rhodopseudomonas acidophila purple bacterium leads to correlations of excitonic energy fluctuations, relevant coherent vibronic coupling, and importantly, a decrease in the excitonic dephasing rates. Combining these effects, we identify a feasible origin for the long-lasting oscillations observed in fluorescent traces from time-delayed two-pulse single-molecule experiments performed on this photosynthetic complex and use this approach to discuss the role of this complementarity in other photosynthetic systems.
非线性光谱揭示了多种光合复合物光学响应中的持久振荡。人们提出了不同的理论模型，这些模型涉及电子（激子）或电子 - 振动（振子）自由度的相干耦合，以解释这些观测结果。随之而来的关于这两种机制相关性的争论可能掩盖了它们的互补性。为了说明这种平衡，我们量化了嗜酸红假单胞菌紫色细菌的LH2单元中的激子离域如何导致激子能量涨落的相关性、相关的相干振子耦合，并且重要的是，导致激子退相速率的降低。综合这些效应，我们为在此光合复合物上进行的延时双脉冲单分子实验的荧光迹线中观察到的持久振荡确定了一个可行的起源，并使用这种方法来讨论这种互补性在其他光合系统中的作用。
