锌细菌叶绿素聚合体中激子弛豫与相干振动动力学研究
文献类型：学位论文
| 作者 | 韩冬佳 |
| 文献子类 | 博士 |
| 导师 | 冷雨欣 |
| 关键词 | 光合作用 Photosynthesis 锌细菌叶绿素聚合体 Zinc chlorin aggregates 超快动力学 Ultra-fast dynamics 泵浦-探测技术 Pump-probe technique |
| 其他题名 | Excitonic Relaxation and Coherent Vibrational Dynamics in Zinc Chlorin Aggregates |
| 英文摘要 | 光合作用是在生物体中将太阳光能转化为稳定化学能的过程,开展光合作用的研究对未来清洁能源的发展具有重要意义。光合作用中一个重要的光能收集功能体即捕光天线系统，主要是以叶绿素分子（或细菌叶绿素分子）为基础的有机复合体，对其超快光弛豫机制的研究是认识光合作用的重要环节。由于天然的光合细菌叶绿素分子结构为层状分布并且没有蛋白质依附，因此可以利用人工合成细菌叶绿素聚合体，如锌细菌叶绿素聚合体，来更简便地研究光合作用中能量传递过程。光合作用原初反应过程一般为捕光天线系统吸收光能，经过能量传递最终到达反应中心，时间尺度范围为十几飞秒到几十皮秒。另一方面，随着近年来飞秒超快激光技术的发展，飞秒激光脉冲泵浦-探测技术被广泛应用于各种超快过程检测中去。因此，利用飞秒激光泵浦-探测技术开展锌细菌叶绿素聚合体中激子弛豫与相干振动动力学研究对于光合作用中超快光弛豫机制的研究具有重要的学术意义和应用价值。 本论文的主要工作是基于非共线光学参量放大（NOPA）技术与色散补偿技术等发展了小于10fs的超宽带飞秒激光，并进一步发展飞秒超短脉冲泵浦-探测技术，对人工合成锌细菌叶绿素聚合体中的超快激子弛豫与振动相干动力学过程进行了研究。本论文取得的主要创新成果和研究进展如下： 1.利用578 ~776nm波段的飞秒泵浦-探测技术研究了锌细菌叶绿素内部动力学过程。所得激子的弛豫动力学过程包含着光吸收过程(photo absorption，中心峰值720nm)和光漂白过程(photo bleaching，中心峰值725nm)。同时，通过对吸收过程分析获得：多激子态（multi- exciton state）到单激子态（single-exciton state）的弛豫时间为100±5fs；Q激子态（Q-exciton state）到无辐射电荷传递态（nonfluorescent charge-transfer state）的弛豫时间为850±70 fs。 2.利用快速傅里叶变换，从二维吸收光谱数据中得到聚合体纯的振动光谱，并发现：细菌叶绿素的振动模式分布趋势与吸收光谱一阶导数一致。这主要是由于基态势能的最低位置与激发态的最低势能在垂直方向存在微小位移差，导致被激发后的波包通过与斜率一致的方向以最快速度到达激发态势能的最低位置。因此，振幅调制最强位置与激子共振的斜率一致。 3.利用负时间飞秒泵浦-探测技术，开展对锌细菌叶绿素聚合体中的量子相干过程研究，发现在探测光超前泵浦光到达样品的情况下，锌细菌叶绿素聚合体中激子相干过程的退相位时间为23±1fs。这一时间对于光合作用中外周捕光天线的初始能量转移过程具有重要意义。同时，获得两个频率为150cm-1和1340cm-1由于激发态波包运动产生振动模式。; Photosynthesis is an important way of organisms in nature to absorb sunlight and convert it into a stable chemical energy. The research of photosynthesis is of great significance for the development of clean energy in the future. One of an important function of light energy collection in photosynthesis is called antenna system, which is mainly on the basis of chlorophyll (or bacteria chlorophyll) organic complex. Therefore, the study of the ultrafast optical relaxation mechanism in these antenna systems is an important part of the understanding of photosynthesis. It has been shown that green photosynthetic bacteria consist the pure pigment bacteriochlorophyll (BChl)-c, d, e with very little structural proteins. So this unique composition allows us syntheting the BChls more easily in vitro, which could be potentially utilized to research the process of energy transfer in photosynthesis. Fast photophysical processes within chlorosomes or chlorosome-like aggregates have been studied by several groups, and many different decay components have been identified from the 100fs to 100ps time scale depending on the species and experimental conditions. Therefore, it is significant to study the ultrafast dynamics in photosynthesis. At the same time, along with the development of laser technology, especially the development of ultrafast laser in recent years, research on ultrafast dynamics of time-resolved technique pump-probe technology has become an important method, which is widely used in various types of ultrafast process and detection. The development of ultrafast laser spectroscopy technology can be used to study the relaxation of exciton states and the dynamics of vibrational levels simultaneously at physiologically relevant temperatures. The main work of this paper is to use the noncollinear optical parametric amplification (NOPA) technology and the dispersion compensation technology, to obtain the sub-10fs broadband femtosecond laser. At the same time, applied this laser to develop pump-probe technique. Finally, the dynamics of coherent vibration coupled to the excitonic transition in zinc chlorin aggregates has been fully studied. The results obtained in the study is of great importance to understand photosynthesis reaction and ultrafast optical relaxation mechanism. This thesis mainly has the following innovative results and major progress: 1. Using 578 ~ 776 nm band of femtosecond pump-probe technology to study the the dynamics process in zinc chlorin aggregates.We obtain that the peaks of photo absorption and bleaching are at 720nm and 725nm, respectively. From the analysis of excitonc relaxation dynamics, two fast relaxation processes are obtained. One is from higher multiexciton state (MES) to the one-exciton state, which takes place in 100±5fs time scales, and the other relaxation is from the Q-exciton state to the dark nonfluorescent charge transfer state, which is determined to be 850±70fs. 2. Using Fast Fourier Transform, the two-dimensional vibrational amplitudes show that the spectral profile of the first derivation of the absorption spectrum have the similar stractrual with vibrational modes distribution. It can be ascribed to small displacement in the coordinate space from the potential minimum of the ground to that of the excited states. Furthermore, resonance energy shift resulted from the each vibrational mode coupled with the excitonic transition has been calculated. 3. Use negative time femtosecond pump-probe technology to study the quantum coherent process in zinc chlorin aggregates. The results for the first time show that the dephasing time of excitonic coherence was 23±1fs by measuring the real-time traces in the negative time scale. Meanwhile, due to the excited state wave-packet motion, the coherent molecular vibrations at 150cm-1 and 1340cm-1 are observed without the influence of the ground state. |
| 学科主题 | 光学工程 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/30931]  |
| 专题 | 中国科学院上海光学精密机械研究所 |
| 作者单位 | 中国科学院上海光学精密机械研究所 |
| 推荐引用方式 GB/T 7714 | 韩冬佳. 锌细菌叶绿素聚合体中激子弛豫与相干振动动力学研究[D]. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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