Transient structure of laser-generated disordered states investigated by ultrafast diffuse X-ray scattering

利用时间分辨X射线漫反射研究了短脉冲激光诱导无序化后材料类液态的结构和动力学。特别是，我们想回答无序态的结构如何依赖于激发强度、无序路径和材料的类型，以及结构如何随时间演变的问题。固体材料的薄箔将受到飞秒激光脉冲的照射。在激光诱导无序之后，LCLS自由电子激光的延迟硬X射线脉冲的散射将以正常入射传输几何形式观察到。作为泵浦-探测时间延迟函数的漫射散射图的测量产生了结构因子的瞬时变化，由此将推导出对关联函数。所提出的实验利用了激发样品在最初几皮秒内的惯性约束，并将提供关于材料在电子激发、温度和压力等极端条件下无序状态的结构性质的信息。

Time-resolved diffuse X-ray scattering will be used to investigate the structure and dynamics of liquid-like states of materials after short-pulse laser-induced disordering. In particular, we would like to answer the question how the structure of the disordered state depends on the excitation strength, the disordering pathway and the type of material, and how the structure evolves over time. Thin foils of solid materials will be irradiated by femtosecond optical laser pulses. Subsequent to the laser-induced disordering the scattering of a timedelayed hard X-ray pulse from the LCLS free electron laser will be observed in normalincidence transmission geometry. Measurements of the diffuse scattering pattern as a function of the pump-probe time delay yield the transient changes of the structure factor from which the pair-correlation function will be derived. The proposed experiments are taking advantage of the inertial confinement of the excited samples during the first few picoseconds and will provide information on the structural properties of disordered states of materials under extreme conditions of electronic excitation, temperature and pressure.