飞秒时间分辨二维电子光谱仪的研制

The real-time observation of electronic coherence is expected as the novel direction in physical chemistry after the realization of observing the vibrational coherence subjected to the wave packet motion of the nuclei in real time. Electronic coherent energy transfer in the photosynthetic and organic macromolecule systems at the ambient temperature have been observed recently, which has been proven as an efficient way of energy transfer. Two-dimensional electronic spectroscopy is a recently developed methodology, which is known as the only mean to observe the electronic coherent dynamics at present. We propose to set up a femtosecond time-resolved two-dimensional electronic spectrometer and utilize it to study the electronic coherence in the energy transfer process of the bacterial photosynthetic antenna light harvesting complexes and the artificial photosynthetic systems. The technique of two-dimensional electronic spectroscopy is based on the phase-stabilized three photon echo method, which record the electronic field and the phase of the photon echo signal by a so-call herodyne detection method with an advantage of background-free detection. Two-dimensional electronic spectrum can be constructed by Fourier transformation of the time domain signals and will be utilized in the investigation of coherent energy transfer process.

电子相干态的实时观测是继振动相干态导致波包核运动实时测量之后化学动力学发展的又一新方向。电子相干态传能途径已经在光合系统及有机高分子体系中被证实，被认为是一种高效传能的新途径。 二维电子相干光谱是近年来发展起来的、也是目前已知的用于研究电子相干态动力学的唯一手段。我们在迫切需要确认细菌光合天线蛋白色素复合体及光合模拟系统中电子相干态传能的情况下，提出建立国内首套飞秒时间分辨二维电子相干光谱实验测量系统。该系统采用飞秒时间分辨三光子回波技术，利用外差测量方法确定光子回波信号的电场和相位，通过两维傅里叶变换构建飞秒时间分辨二维电子光谱，并最终用于光合系统及人工模拟体系相干电子态传能过程的测量。

根据项目申请与计划书的研究内容，成功研制了一台飞秒时间分辨二维电子光谱仪，设备技术指标为：单元光谱数据采集时间段内（6分钟）相位稳定性为λ/120，并且该系统的相干时间延迟线具有最小时间分辨5.7阿秒，经傅里叶变换后获得的二维光谱分辨率可达20波数,实现了项目的预期验收指标。该装置相位稳定性指标接近国际同类设备的最好水平。 . 所研制的二维电子相干光谱仪包括10飞秒，20飞秒非共线光参量放大器个1台，基于衍射光学分光及分束镜分光的飞秒时间分辨二维电子态相干光谱仪各1台（光路部分不同），并编写了配套的labview语言仪器控制软件与matlab语言数据处理软件各1套。应用上述设备，我们研究了细菌叶绿素分支的低振动频模与电子态耦合的相干激发，发现了新的科学现象，即不同振动模在共振拉曼激发过程中的相干耦合，并在实验的基础上提出了新的理论机制，即二维光谱中的多振动模相干耦合的机制。在本项目支持下，编写超快光谱教科书1本，发表论文5篇，申请专利1个，培养博士生7名。.二维电子光谱学方法具有广泛的应用空间，如揭示光合系统中的量子现象、能量传递方式、路径，有机聚合物的单线态分裂，耦合量子阱体系的多体效应等。因此，二维电子光谱装置已由最初的光合体系的超快光谱研究扩展到有机物、半导体材料等领域，我们相信二维电子光谱在未来的超快光谱研究领域将发挥越来越重要的作用。