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Study on the local structural change associated with the photo-induced phase transition in single crystals of quasi-one dimensional charge-transfer complex TTF-CA.

准一维电荷转移复合物TTF-CA单晶中与光致相变相关的局部结构变化的研究。

基本信息

批准号：
13440096
负责人：
ITOH Chihiro
金额：
$ 8.51万
依托单位：
Wakayama University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

项目摘要

Crystals of quasi one-dimensional charge-transfer complex TTF-CA show structural phase transition between quasi-neutral phase, in which the donors (TTFs) and the acceptors (CAs) are almost neutral, and quasi-ionic phases, in which the partially ionized TTFs and CAs form heterodimers. Since the discovery of the photo-induced phase transition (PIPT) of the ionic phase of the TTF-CA crystal, many efforts have been made for revealing the PIPT's dynamics. However, identification and characterization of the photo-induced phase (PIP) has not been made yet. In the present study, we carried out electron-spin echo detection of electron spin resonance (ESE-ESR) and Fourier-transformation infrared (FT-IR) measurement for characterizing the PIP of TTF-CA crystal. For proving the local structure of the ionic phase and the PIP, we utilized spin solitons formed between two degenerated structures of the ionic phase as a spin probe. The symmetry and the local structural information of the spin soliton a … More t 4 K was obtained by measuring angular dependence of the ESE-ESR spectra at 4 K, and by using electron-spin echo envelope modulation (ESEEM) technique. The results suggest that the spin soliton has the configuration of unpaired ionized molecule. When the crystal was excited continuously by the 523-nm laser beam having the E vector perpendicular to the stacking axis, the ESE-ESR signal arising from the spin solitons was reduced largely. On the other hand, the excitation with E vector parallel to the stacking axis gave small change. By time-resolved ESE-ESR measurements, the ESR signal due to the spin solitons was largely affected in the μs region even by the excitation with the E vector parallel to the stacking axis. The result suggests that the laser excitation leads to temporal change in the configuration of the spin solitons even when the excitation is insufficient for inducing the phase transition. By FT-IR measurements under weak excitation, we have revealed that the charge-transfer absorption of the crystal was largely affected. The result suggests that the donor-acceptor pairs are partially dissociated. Less

准一维电荷转移络合物TTF-CA的晶体在准中性相和准离子相之间发生结构相变，准中性相中施主和受主几乎为中性，准离子相中部分电离的TTF和CaS形成杂二聚体。自从TTF-CA晶体的离子相光致相变(PIPT)被发现以来，人们为揭示PIPT的动力学做了大量的工作。然而，对光诱导相(PIP)的鉴定和表征还没有得到证实。在本研究中，我们进行了电子自旋回波(ESE-ESR)检测和傅里叶变换红外(FT-IR)测量，以表征TTF-CA晶体的PIP。为了证明离子相和PIP的局域结构，我们使用在离子相的两个简并结构之间形成的自旋孤子作为自旋探针。自旋孤子a…的对称性和局域结构信息通过测量4K下ESE-ESR谱的角度相关性，并利用电子自旋回波包络调制(ESEEM)技术，获得了更高的t4K。结果表明，自旋孤子具有未成对的电离分子构型。当用E矢量垂直于堆积轴的523 nm激光连续激发晶体时，由自旋孤子产生的ESE-ESR信号大大减少。而E矢量平行于堆积轴的激发则变化不大。通过时间分辨的电子自旋共振测量，在μS区，即使在E矢量平行于堆积轴的激发下，自旋孤子产生的电子自旋共振信号也受到很大的影响。结果表明，即使在激光激发不足以引起相变的情况下，激光激发也会导致自旋孤子位形的时间变化。在弱激发下的FT-IR测试表明，该晶体的电荷转移吸收受到很大影响。结果表明，供体-受体对部分解离。较少