100 Picosecond Diffraction Catches Structural Transients of Laser-Pulse Triggered Switching in a Spin-Crossover Crystal
100 Picosecond Diffraction Catches Structural Transients of Laser-Pulse Triggered Switching in a Spin-Crossover Crystal
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DOI：
10.1002/chem.201103048
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发表时间：
2012-02-01
影响因子：
4.3
通讯作者：
Buron-Le Cointe, Marylise
中科院分区：
文献类型：
--
作者：
Collet, Eric;Lorenc, Maciej;Buron-Le Cointe, Marylise
用100皮秒X射线衍射研究了自旋交叉配合物[（TPA）Fe（TCC）] PF_6的正交多晶型单晶的光开关动力学。在动态结构科学的新兴领域的框架中，这是通过使用光泵/X射线探针技术，这允许以下真实的时间结构重组在分子内和分子间水平与晶体中的自旋状态的变化。我们在这里使用的时间结构的同步辐射产生100皮秒的X射线脉冲，耦合到100 fs的激光激发。这项研究揭示了丰富多样的结构重组，与动力学过程的不同步骤。三个连续的制度证明在时域：1）局部分子光开关与结构重组在恒定的体积，2）体积弛豫与局部温度的不均匀分布，3）均匀化的晶体在瞬态100 μ s激光激发后。这些发现是从根本上不同于那些长寿命的光致高自旋态的传统衍射研究。这里使用的时间分辨率与皮秒X射线衍射探针不同的物理量在其固有的时间尺度上，在连续的过程中驱动功能化材料的宏观切换脱落新的光。这些结果为远离平衡态的结构研究铺平了道路，并代表了迈向飞秒晶体学的第一步。
We study by 100 picosecond X-ray diffraction the photo-switching dynamics of single crystal of the orthorhombic polymorph of the spin-crossover complex [(TPA)Fe(TCC)]PF6, in which TPA=tris(2-pyridyl methyl)amine, TCC2-=3,4,5,6-Cl4-Catecholate2-. In the frame of the emerging field of dynamical structural science, this is made possible by using optical pump/X-ray probe techniques, which allow following in real time structural reorganization at intra- and intermolecular levels associated with the change of spin state in the crystal. We use here the time structure of the synchrotron radiation generating 100 picosecond X-ray pulses, coupled to 100 fs laser excitation. This study has revealed a rich variety of structural reorganizations, associated with the different steps of the dynamical process. Three consecutive regimes are evidenced in the time domain: 1) local molecular photo-switching with structural reorganization at constant volume, 2) volume relaxation with inhomogeneous distribution of local temperatures, 3) homogenization of the crystal in the transient state 100 mu s after laser excitation. These findings are fundamentally different from those of conventional diffraction studies of long-lived photoinduced high spin states. The time-resolution used here with picosecond X-ray diffraction probes different physical quantities on their intrinsic time-scale, shedding new light on the successive processes driving macroscopic switching in a functionalized material. These results pave the way for structural studies away from equilibrium and represent a first step toward femtosecond crystallography.