Development of High Energy Resolution Anomalous X-ray Scattering Instrumentation for High-Brilliance Synchrotron Beamlines

这份来自化学研究仪器和设施（CRIF）项目和综合活动办公室主要研究仪器（MRI）项目的合同将支持开发精确可靠的异常x射线衍射（AXD）光谱仪，该光谱仪由高能量分辨率窄带通晶体光学单色仪和晶体分析仪组成。这是北伊利诺伊大学物理系的苏珊·米尼和芝加哥大学高级辐射源联盟（CARS）的两位科学家蒂莫西·格雷伯和p·詹姆斯·维卡罗的团队合作成果。该光谱仪将允许利用原子在吸收边缘附近的散射截面上的全部能量色散。该仪器将安装在先进光子源（APS）的光束线15上，主要用于价特异性静态和时间分辨化学晶体学实验。应用包括研究大磁阻氧化物，软材料的表面和界面特性以及聚合物的时间依赖性研究。AXD技术将有助于解决含有混合价原子的未知晶体结构，与中子衍射和局部探针（如x射线吸收光谱）互补。AXD还将提供一种有用的方法来研究具有不同类型配位几何的单一氧化态元素的行为。目前，AXD研究以几个eV的能量分辨率进行，这防止了一个特定价原子的结构因子对另一个原子的选择性修饰。该仪器具有更高的分辨率，结合APS的高光谱亮度，将对固态和材料科学产生重大影响。

This award from the Chemistry Research Instrumentation and Facilities (CRIF) Program and the Major Research Instrumentation (MRI) Program of the Office of Integrative Activities will support the development of an accurate and reliable anomalous x-ray diffraction (AXD) spectrometer consisting of a high-energy-resolution narrow-band-pass crystal-optics monochromator and crystal analyzer. This is a team effort involving Susan Mini of the Physics Department at Northern Illinois University and Timothy Graber and P. James Viccaro, both scientists at The Consortium for Advanced Radiation Sources (CARS) of The University of Chicago. The spectrometer will allow utilization of full energy dispersion in scattering cross-section of atoms near the absorption edge. The instrumentation, which will be installed on beamline 15 at the Advanced Photon Source (APS), will be used primarily for valence-specific static and time-resolved chemical crystallography experiments. Applications include studies on large magnetoresistive oxides, surfaces and interfacial properties of soft materials and time-dependent studies of polymers. The AXD technique will help solve unknown crystal structures containing mixed-valent atoms in a way complementary to neutron diffraction and local probes such as x-ray absorption spectroscopy. AXD will also provide a useful method to study the behavior of an element in a single oxidation state with different types of coordination geometry. Currently, AXD studies are carried out with energy resolution of a few eV, which prevents selective modification of the structure factor of atoms of one particular valence over another. This instrument, with its significantly higher resolution, combined with the high spectral brilliance of the APS, will have significant impact in solid-state and materials science.