Nonlinear interaction of excitons and photoinduced phase transition in quasi-one dimensional organic charge-transfer crystals

准一维有机电荷转移晶体中激子的非线性相互作用和光致相变

基本信息

批准号：
11215204
负责人：
TANIMURA Katsumi
金额：
$ 35.52万
依托单位：
Osaka University (2001)Nagoya University (1999-2000)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research on Priority Areas (B)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

项目摘要

The purpose of this project is to clarify the dynamics of photoinduced ionic-to-neutral phase transition (NI transition) in one-dimensional organic charge-transfer crystal of tetrathiafulvalen-p-chloranil (TTF-CA) for understanding the mechanism of this photoinduced process from microscopic point of view. We have studied the temporal evolution of the process by means of time-resolved reflectance spectroscopy in temporal domains of sub-ps, and the state-sensitive efficiency of the phase transition by means of excitation spectroscopy, using a tunable ns laser from 266 to 2000 nm. Main results obtained are summarized below.1) The whole process of the photoinduced NI transition in TTF-CA consists of the three sequential primary steps ; the first is the precursor-forming process at a few ps after excitation, the second is the process of local proliferation around 50 ps after excitation, and the third is the process of forming N-phase orders, lasting over 300 ps.2) The process of precursor formation is nonlinear in the sense that one-absorbed photon converts the charge state of as many as a few hundreds of donor-acceptor molecules to form individual neutral-molecular clusters on stack chains. The proliferation in this process is strongly excitation-wavelength dependent, showing the initial-condition sensitivity in this photoinduced transformation.3) The second and third processes are associated with nonlinear proliferation of photoinduced changes ; the magnitudes of proliferation depend strongly on the amount of the precursor photoinduced. This proliferation of nonlinear relaxation also dependents on temperature, and the magnitude is governed by an activation energy of 0.01eV, which roughly corresponds to the free-energy difference between the two phases.These results have provided us crucial knowledge for establishing thorough understanding of the mechanism of this photoinduced phase transition.

该项目的目的是阐明在四维富瓦伦-P-氯酸酯（TTF-CA）的一维有机电荷转移晶体中光诱导的离子到中和相变的动力学，以理解从微观观点的观点观点的这种光诱导过程的机制。我们使用266至2000 nm的可调ns激光器使用可调的NS激光，研究了子PS时间域中的时间分解反射光谱的时间演变，以及通过激发光谱的状态转变的状态敏感效率。在下面总结了所获得的主要结果。1）TTF-CA中光诱导的Ni转变的整个过程由三个顺序主要步骤组成； the first is the precursor-forming process at a few ps after excitation, the second is the process of local proliferation around 50 ps after excitation, and the third is the process of forming N-phase orders, lasting over 300 ps.2) The process of precursor formation is nonlinear in the sense that one-absorbed photon converts the charge state of as many as a few hundreds of donor-acceptor molecules to form individual neutral-molecular堆栈链条上的簇。该过程中的增殖非常依赖于激发波长，显示了这种光诱导的转化中的初始条件灵敏度。3）第二和第三过程与光诱导的变化的非线性增殖有关；增殖的幅度在很大程度上取决于图片诱导的前体的量。非线性弛豫的这种增殖也取决于温度，大小由0.01EV的激活能约束，这大致与两个阶段之间的自由能差相对应。这些结果为我们提供了至关重要的知识，以建立对这种光诱导的相变机理的彻底理解。