Advanced Science Institute, RIKEN, Wako, Saitama, Japan.
J Chem Phys. 2011 Jun 28;134(24):244103. doi: 10.1063/1.3600341.
We investigate the quantum dynamics of energy and charge transfer in a wheel-shaped artificial photosynthetic antenna-reaction center complex. This complex consists of six light-harvesting chromophores and an electron-acceptor fullerene. To describe quantum effects on a femtosecond time scale, we derive the set of exact non-Markovian equations for the Heisenberg operators of this photosynthetic complex in contact with a Gaussian heat bath. With these equations we can analyze the regime of strong system-bath interactions, where reorganization energies are of the order of the intersite exciton couplings. We show that the energy of the initially excited antenna chromophores is efficiently funneled to the porphyrin-fullerene reaction center, where a charge-separated state is set up in a few picoseconds, with a quantum yield of the order of 95%. In the single-exciton regime, with one antenna chromophore being initially excited, we observe quantum beatings of energy between two resonant antenna chromophores with a decoherence time of ∼100 fs. We also analyze the double-exciton regime, when two porphyrin molecules involved in the reaction center are initially excited. In this regime we obtain pronounced quantum oscillations of the charge on the fullerene molecule with a decoherence time of about 20 fs (at liquid nitrogen temperatures). These results show a way to directly detect quantum effects in artificial photosynthetic systems.
我们研究了轮状人工光合作用天线-反应中心复合物中能量和电荷转移的量子动力学。该复合物由六个光捕获色素和一个电子受体富勒烯组成。为了在飞秒时间尺度上描述量子效应，我们推导出了与高斯热浴接触的这种光合作用复合物的海森堡算符的一组精确非马尔可夫方程。有了这些方程，我们可以分析强系统-浴相互作用的 regime，其中重组能与相间激子耦合的 order 相当。我们表明，最初激发的天线色素的能量被有效地引导到卟啉-富勒烯反应中心，在几皮秒内建立电荷分离状态，量子产率约为 95%。在单激子 regime 中，最初激发一个天线色素，我们观察到两个共振天线色素之间的能量量子拍频，相干时间为∼100 fs。我们还分析了双激子 regime，当反应中心中最初激发两个卟啉分子时。在这个 regime 中，我们得到了富勒烯分子上电荷的明显量子振荡，相干时间约为 20 fs（在液氮温度下）。这些结果表明了一种在人工光合作用系统中直接检测量子效应的方法。
