Structure and formation dynamics of the photo-induced phase transition in Fe spincrossover complexes

光致相变（PIPT）是非平衡物理中一个非常引人注目的现象。在远离热平衡的体系中，人们期待着新的自组织结构。在本计画中，我们以光致自旋交叉跃迁为研究对象，利用拉曼散射、红外吸收、EXAFS及X光绕射等技术，探讨光致宏观相的结构。在菲皮克。配合物中，只有在拉曼散射实验中发现热诱导态和光诱导态的高自旋态有较大的差异，而EXAFS和X射线衍射表明光诱导态的键长和长程有序度与高温高自旋态的键长和长程有序度非常相似。讨论了对称性降低的可能性。此外，我们还测量了双核自旋交叉配合物[Fe（bt）（NCS）_2]_2（bpym）的光诱导PIPT现象，发现了一个自旋选择性PIPT，它通过一个中间态发生两步热相变。测量了样品的拉曼散射和红外吸收，并用唯象模型进行了讨论。利用太赫兹光谱仪结合ATR技术测量了自旋交叉复合物中的氢键。

Photo-induced phase transition(PIPT) is quite attractive phenomenon for non-equilibrium physics. Novel self-organized structure is expected in a system far from thermal equilibrium. In this project, we focued on the photo-induced spin-crossover transition and explored the structure of the photo-induced macroscopic phase using Raman scattering, infrared absorption, EXAFS, and X-ray diffraction techniques. In Fe-pic. complexes, large difference was found between thermally and light-induced high-spin states only in the Raman scattering experiments, whereas the EXAFS and X-ray diffraction revealed that the bond-lengths and long range order in the photo-induced phase are quite similar to those in the high temperature high spin phase. Possibility of the symmetry lowering was discussed. In addition, we measured photo-induced phenomena and found a spin-selective PIPT in binuclear spin-crossover complex, [Fe(bt)(NCS)_2]_2(bpym) that shows two step thermal phase transition via an intermediate state. The Raman scattering and infrared absorption are measured and discussed with a phenomenological model. A Terahertz spectrometer that is combined with ATR technique was developed to measure a hydrogen bonging in the spin-crossover complexes.