Badali Daniel S, Dwayne Miller R J
Hamburg Centre for Ultrafast Imaging, Department of Physics, Max Planck Institute for the Structure and Dynamics of Matter, University of Hamburg, Hamburg 22761, Germany.
Struct Dyn. 2017 Jun 2;4(5):054302. doi: 10.1063/1.4985059. eCollection 2017 Sep.
In conjunction with ultrafast diffraction, streak cameras offer an unprecedented opportunity for recording an entire molecular movie with a single probe pulse. This is an attractive alternative to conventional pump-probe experiments and opens the door to studying irreversible dynamics. However, due to the "smearing" of the diffraction pattern across the detector, the streaking technique has thus far been limited to simple mono-crystalline samples and extreme care has been taken to avoid overlapping diffraction spots. In this article, this limitation is addressed by developing a general theory of streaking of time-dependent diffraction patterns. Understanding the underlying physics of this process leads to the development of an algorithm based on Bayesian analysis to reconstruct the time evolution of the two-dimensional diffraction pattern from a single streaked image. It is demonstrated that this approach works on diffraction peaks that overlap when streaked, which not only removes the necessity of carefully choosing the streaking direction but also extends the streaking technique to be able to study polycrystalline samples and materials with complex crystalline structures. Furthermore, it is shown that the conventional analysis of streaked diffraction can lead to erroneous interpretations of the data.
与超快衍射相结合，条纹相机为用单个探测脉冲记录整个分子电影提供了前所未有的机会。这是传统泵浦 - 探测实验的一个有吸引力的替代方案，并为研究不可逆动力学打开了大门。然而，由于衍射图案在探测器上的“拖尾”现象，条纹技术迄今为止仅限于简单的单晶样品，并且一直非常小心地避免衍射斑点重叠。在本文中，通过发展时间相关衍射图案条纹化的一般理论来解决这一限制。理解这一过程的基本物理原理促使开发一种基于贝叶斯分析的算法，用于从单个条纹图像重建二维衍射图案的时间演化。结果表明，这种方法适用于条纹化时重叠的衍射峰，这不仅消除了仔细选择条纹化方向的必要性，还将条纹技术扩展到能够研究多晶样品和具有复杂晶体结构的材料。此外，结果表明，对条纹化衍射的传统分析可能导致对数据的错误解释。
