Hua Nelson, Zaluzhnyy Ivan A, Hrkac Stjepan B, Shabalin Anatoly G, Shpyrko Oleg G
Department of Physics, University of California, San Diego, La Jolla, CA 92093, USA.
J Synchrotron Radiat. 2020 Nov 1;27(Pt 6):1626-1632. doi: 10.1107/S1600577520012345. Epub 2020 Oct 19.
Pump-probe experiments at synchrotrons and free-electron lasers to study ultrafast dynamics in materials far from equilibrium have been well established, but techniques to investigate equilibrium dynamics on the nano- and pico-second timescales remain underdeveloped and experimentally challenging. A promising approach relies on a double-probe X-ray speckle visibility spectroscopy setup at split-and-delay beamlines of X-ray free-electron lasers. However, the logistics in consistently producing two collinear, perfectly overlapping pulses necessary to conduct a faithful experiment is difficult to achieve. In this paper, a method is introduced to extract contrast in the case where an angular misalignment and imperfect overlap exists between the two pulses. Numerical simulations of a dynamical system show that contrast can still be extracted for significant angular misalignments accompanied by partial overlap between the two pulses.
利用同步加速器和自由电子激光进行泵浦-探测实验来研究远离平衡态的材料中的超快动力学已经相当成熟，但在纳秒和皮秒时间尺度上研究平衡态动力学的技术仍不发达且在实验上具有挑战性。一种有前景的方法依赖于在X射线自由电子激光的分离和延迟光束线上设置的双探针X射线散斑可见度光谱装置。然而，要持续产生进行可靠实验所需的两个共线、完美重叠的脉冲，其后勤保障很难实现。本文介绍了一种在两个脉冲之间存在角度失准和不完全重叠的情况下提取对比度的方法。一个动力学系统的数值模拟表明，对于两个脉冲之间存在显著角度失准且伴有部分重叠的情况，仍然可以提取对比度。
