Two-dimensional spectroscopy of a molecular dimer unveils the effects of vibronic coupling on exciton coherences
Two-dimensional spectroscopy of a molecular dimer unveils the effects of vibronic coupling on exciton coherences
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DOI：
10.1038/nchem.1834
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发表时间：
2014-03-01
期刊：
影响因子：
21.8
通讯作者：
Miller, R. J. Dwayne
中科院分区：
文献类型：
--
作者：
Halpin, Alexei;Johnson, Philip J. M.;Miller, R. J. Dwayne
蛋白质-色素复合物多维光谱中持续振荡信号的观测引起了关于相干辅助电子能量转移作为光合作用关键操作原理的作用的争论。振动耦合最近被提出作为所观察到的光谱拍频的长寿命的解释。然而，光合作用系统本质上是复杂的，需要对简单分子化合物进行易于处理的研究，以充分理解其基础物理学。在这项工作中，我们提出了测量和计算的溶剂化分子的同二聚体在相应的二维光谱中具有清晰的可分辨的振荡。通过分析各种因素对非线性响应的影响，我们成功地分离出了激子间相干的信号。我们发现，虽然计算预测这种相干性的延长，由于振动耦合，动态无序和振动弛豫的组合导致的相干性衰减的时间尺度上的电子退相时间。
The observation of persistent oscillatory signals in multidimensional spectra of protein-pigment complexes has spurred a debate on the role of coherence-assisted electronic energy transfer as a key operating principle in photosynthesis. Vibronic coupling has recently been proposed as an explanation for the long lifetime of the observed spectral beatings. However, photosynthetic systems are inherently complicated, and tractable studies on simple molecular compounds are needed to fully understand the underlying physics. In this work, we present measurements and calculations on a solvated molecular homodimer with clearly resolvable oscillations in the corresponding two-dimensional spectra. Through analysis of the various contributions to the nonlinear response, we succeed in isolating the signal due to inter-exciton coherence. We find that although calculations predict a prolongation of this coherence due to vibronic coupling, the combination of dynamic disorder and vibrational relaxation leads to a coherence decay on a timescale comparable to the electronic dephasing time.