标题： 衍射图样在二维密集单分散系统中的交叉相关分析中的相干性作用 显示英文标题

标题： The role of the coherence in the cross-correlation analysis of diffraction patterns from two-dimensional dense mono-disperse systems

摘要： 对胶体系统的静态和动态结构特性的研究依赖于能够在实空间中实现原子分辨率并在时间上实现飞秒分辨率的技术。 最近，对稀释和致密聚集体的X射线和电子衍射图样的交叉相关函数（CCF）分析已经证明了其在获取样品局部有序性和对称性信息方面的能力。 关于束流相干性在衍射图样形成以及CCF特性中的作用，尤其是在致密系统中，仍然存在未解的问题。 在这里，我们模拟了不同对称性的致密二维单分散系统的衍射图样，改变探测波的横向相干性，并分析它们的CCF。 我们在不同的尺寸尺度下研究具有不同对称性的样品，例如排列成四重晶格的五聚体，其中每个五聚体被三角晶格包围，包括有序和无序的情况。 在这样的系统中，特定的散射矢量处会在CCF中出现不同的对称性调制。 我们证明了CCF的幅度是样品有序程度的特征，并且在部分横向相干的情况下，致密样品的CCF对应于单个散射物体的CCF。 显示英文摘要

摘要： The investigation of the static and dynamic structural properties of colloidal systems relies on techniques capable of atomic resolution in real space and femtosecond resolution in time. Recently, the cross-correlation function (CCF) analysis of both X-rays and electron diffraction patterns from dilute and dense aggregates has demonstrated the ability to retrieve information on the sample's local order and symmetry. Open questions remain regarding the role of the beam coherence in the formation of the diffraction pattern and the properties of the CCF, especially in dense systems. Here, we simulate the diffraction patterns of dense two-dimensional monodisperse systems of different symmetries, varying the transverse coherence of the probing wave, and analyze their CCF. We study samples with different symmetries at different size scale, as for example, pentamers arranged into a four-fold lattice where each pentamer is surrounded by triangular lattices, both ordered and disordered. In such systems, different symmetry modulations are arising in the CCF at specific scattering vectors. We demonstrate that the amplitude of the CCF is a fingerprint of the degree of the ordering in the sample and that at partial transverse coherence, the CCF of a dense sample corresponds to that of an individual scattering object.