Cailleau Hervé, Lorenc Maciej, Guérin Laurent, Servol Marina, Collet Eric, Buron-Le Cointe Marylise
Institut de Physique de Rennes, Université de Rennes1-CNRS, UMR 6251, F-35042 Rennes, France.
Acta Crystallogr A. 2010 Mar;66(Pt 2):189-97. doi: 10.1107/S0108767309051046. Epub 2010 Feb 18.
Fast and ultra-fast time-resolved diffraction is a fantastic tool for directly observing the structural dynamics of a material rearrangement during the transformation induced by an ultra-short laser pulse. The paper illustrates this ability using the dynamics of photoinduced molecular switching in the solid state probed by 100 ps X-ray diffraction. This structural information is crucial for establishing the physical foundations of how to direct macroscopic photoswitching in materials. A key feature is that dynamics follow a complex pathway from molecular to material scales through a sequence of processes. Not only is the pathway indirect, the nature of the dynamical processes along the pathway depends on the timescale. This dictates which types of degrees of freedom are involved in the subsequent dynamics or kinetics and which are frozen or statistically averaged. We present a recent investigation of the structural dynamics in multifunctional spin-crossover materials, which are prototypes of molecular bistability in the solid state. The time-resolved X-ray diffraction results show that the dynamics span from subpicosecond molecular photoswitching followed by volume expansion (on a nanosecond timescale) and additional thermoswitching (on a microsecond timescale).
快速和超快时间分辨衍射是一种非常出色的工具，可用于直接观察在超短激光脉冲诱导的转变过程中材料重排的结构动力学。本文利用100皮秒X射线衍射探测的固态光致分子开关动力学来说明这种能力。这种结构信息对于建立如何在材料中引导宏观光开关的物理基础至关重要。一个关键特征是，动力学通过一系列过程遵循从分子尺度到材料尺度的复杂路径。不仅路径是间接的，沿路径的动力学过程的性质还取决于时间尺度。这决定了在随后的动力学或动力学中涉及哪些类型的自由度，以及哪些被冻结或统计平均。我们展示了对多功能自旋交叉材料中结构动力学的最新研究，这些材料是固态分子双稳态的原型。时间分辨X射线衍射结果表明，动力学范围从亚皮秒分子光开关，随后是体积膨胀（在纳秒时间尺度上）和额外的热开关（在微秒时间尺度上）。
