Song Ki-Hee, Gu Munui, Kim Min-Seok, Kwon Hyeok-Jun, Rhee Hanju, Han Hogyu, Cho Minhaeng
Space-Time Resolved Molecular Imaging Research Team, Korea Basic Science Institute (KBSI) , Seoul 136-713, Korea.
Department of Chemistry, Korea University , Seoul 136-701, Korea.
J Phys Chem Lett. 2015 Nov 5;6(21):4314-8. doi: 10.1021/acs.jpclett.5b02030. Epub 2015 Oct 16.
The origin of quantum coherence in two-dimensional (2D) electronic spectra of molecular aggregates and light-harvesting complexes still remains an open question. In particular, it could be challenging to distinguish between electronic and vibrational coherences for a coupled system, where both degrees of freedom can be simultaneously excited. In this Letter, we examine quantum beats in the 2D spectra of zinc naphthalocyanine (ZnNc) aggregate and monomer, and compare their characteristic features in terms of the frequency and relative phase of diagonal and off-diagonal amplitude oscillations. The long-lasting oscillating components (>1 ps) at 600-700 cm(-1) observed in both the aggregate and monomer are found to be attributed to the vibrational coherence. The wide phase variations of the 2D spectral amplitude oscillations are observed not just in the aggregate but also in the monomer state. This suggests that the unusual 90° phase shift may be attributed to neither quantum population-to-coherence transfer nor vibronic exciton coupling.
分子聚集体和光捕获复合物二维（2D）电子光谱中量子相干的起源仍然是一个悬而未决的问题。特别是，对于一个耦合系统，区分电子相干和振动相干可能具有挑战性，因为这两个自由度可以同时被激发。在本信函中，我们研究了锌萘酞菁（ZnNc）聚集体和单体的二维光谱中的量子拍，并根据对角和非对角振幅振荡的频率和相对相位比较了它们的特征。在聚集体和单体中均观察到的600 - 700 cm⁻¹处持续时间较长（>1 ps）的振荡成分被发现归因于振动相干。二维光谱振幅振荡的宽相位变化不仅在聚集体中观察到，在单体状态下也观察到。这表明这种不寻常的90°相移可能既不归因于量子布居到相干的转移，也不归因于振动电子激子耦合。
