Beck Christian, Roosen-Runge Felix, Grimaldo Marco, Zeller Dominik, Peters Judith, Schreiber Frank, Seydel Tilo
Institut für Angewandte Physik Universität Tübingen Auf der Morgenstelle 10 72076Tübingen Germany.
Institut Max von Laue-Paul Langevin, 71 Avenue des Martyrs, 38042Grenoble, France.
J Appl Crystallogr. 2024 Jun 7;57(Pt 4):912-924. doi: 10.1107/S1600576724003820. eCollection 2024 Aug 1.
Neutron spectroscopy uniquely and non-destructively accesses diffusive dynamics in soft and biological matter, including for instance proteins in hydrated powders or in solution, and more generally dynamic properties of condensed matter on the molecular level. Given the limited neutron flux resulting in long counting times, it is important to optimize data acquisition for the specific question, in particular for time-resolved (kinetic) studies. The required acquisition time was recently significantly reduced by measurements of discrete energy transfers rather than quasi-continuous neutron scattering spectra on neutron backscattering spectrometers. Besides this reduction in acquisition times, smaller amounts of samples can be measured with better statistics, and most importantly, kinetically changing samples, such as aggregating or crystallizing samples, can be followed. However, given the small number of discrete energy transfers probed in this mode, established analysis frameworks for full spectra can break down. Presented here are new approaches to analyze measurements of diffusive dynamics recorded within fixed windows in energy transfer, and these are compared with the analysis of full spectra. The new approaches are tested by both modeled scattering functions and a comparative analysis of fixed energy window data and full spectra on well understood reference samples. This new approach can be employed successfully for kinetic studies of the dynamics focusing on the short-time apparent center-of-mass diffusion.
中子光谱学能够以独特且非破坏性的方式研究软物质和生物物质中的扩散动力学，例如水合粉末或溶液中的蛋白质，更广泛地说，还能研究凝聚态物质在分子水平上的动力学性质。由于中子通量有限，导致计数时间较长，因此针对特定问题优化数据采集非常重要，特别是对于时间分辨（动力学）研究而言。最近，通过在中子背散射光谱仪上测量离散能量转移而非准连续中子散射光谱，所需的采集时间大幅减少。除了采集时间的减少外，还可以用更好的统计数据测量少量样品，最重要的是，可以跟踪动力学变化的样品，例如聚集或结晶的样品。然而，鉴于这种模式下探测的离散能量转移数量较少，用于全光谱的既定分析框架可能会失效。本文介绍了分析在能量转移固定窗口内记录的扩散动力学测量的新方法，并将这些方法与全光谱分析进行了比较。通过模拟散射函数以及对已充分了解的参考样品的固定能量窗口数据和全光谱进行比较分析，对新方法进行了测试。这种新方法可以成功地用于聚焦于短时间表观质心扩散的动力学研究。
