PHOTOINDUCED PHASE TRANSITION IN QUASI ONE-DIMENSIONAL ORGANIC CRYSTALS BY MEANS OF THE-RESOLVED RAMAN SCATTERING SPECTROSCOPY

这项研究的目的是基于超短时间域的动力学和结构性质的直接信息，建立对准一维有机晶体光致结构转变机制的一般理解。因此，飞秒时间分辨光学方法和时间分辨拉曼光谱方法被广泛应用。对于四硫富瓦烯-对氯苯醚(TTF-CA)的电荷转移有机晶体，我们可以完全分辨出转变过程中连续的三个主要步骤：前驱体形成步骤、局部扩散步骤和N相有序形成步骤。通过多波长反射测量的结果，得到了每一步的微观认识。对于在二乙炔晶体中形成准一维共轭It键序的过程，在5，7-十二碳二炔-1，12-二醇双[氨基甲酸苯酯](TCDU)晶体中，阐明了聚合反应中双自由基中间体的形成动力学：三重态-激子融合产生二聚自由基。通过应用拉曼光谱，我们可以获得聚合的每个步骤的精确结构知识，从双自由基到二卡宾，原基，最后是它的键链。所形成的聚二乙炔晶体既有A相又有B相，并用费秒时间分辨反射光谱研究了每一相的弛豫动力学。虽然这种聚TCDU没有诱导光诱导相变，但我们发现了形成本征亚稳态的重要过程。本项目的研究结果为我们在微观理解光诱导相变过程中每一步的结构知识的基础上构建光诱导相变的机理提供了重要的依据。

The purpose of this research project was to establish general understanding of the mechanism of photoinduced structural transformation in quasi one-dimensional organic crystals, based on the dynamics in ultra short temporal domain and on the direct information on structural properties. For this, femtosecond time-resolved optical methods and time-resolved Raman spectroscopic methods were extensively used.For a charge-transfer organic crystal of tetrathiafulvalen-p-chloranil (TTF-CA), we could resolve completely the three consecutive primary steps involved in the transition ; the precursor-forming step, local proliferation, and N-phase order formation. The microscopic understanding in each step has been obtained by the results of multi-wavelength reflection measurements. For a process of forming a quasi one-dimensional conjugated it-bond order in diacetylene crystals, dynamics in forming the key entity of di-radical intermediatd in the polymerization reactions has been elucidated in 5,7-dodecadiyne-1,12-diol bis[phenyl carbamate] (TCDU) crystals : triplet-exciton fusion generates dimer diradicals. By applying Raman spectroscopy, we could obtain precise structural knowledge on each step of polymerization from diradicals to dicarben, origornaers and finally it-bond chains. The polydiacetylene crystals thus formed show both A and B phases, and relaxation dynamics in each phase have been studied by ferntosecond time-resolved reflection spectroscopy. Although photoinduced phase transition has not been induced in this poly TCDU, important process of forming intrinsic meta-stable states has been discovered.The results obtained in the present project have provided the important basis on which we can construct the mechanism of photoinudced phase transition based on microscopic understanding of structural knowledge in each step involved in the process.