High Resolution Crystallographic Studies Using Synchrotron Radiation

9317770在化学系物理化学项目中，纽约州立大学布法罗分校的P.Coppens教授将利用布鲁克海文国家实验室的国家同步辐射光源从事结晶学研究，并使用先进的传统设施进行实验。这项研究包括几个部分：应用X射线的反常散射来选择性地识别位置空位，确定固体中原子的氧化态和识别光谱转变；研究晶体对外部扰动的响应，如激光诱导的分子激发；以及对调制和复合固体的分析，这些固体至少在一个方向上是非周期性的。超低温单晶技术将被用来分析晶体中的电荷密度，并研究低维导电固体结构的温度依赖性。在开发了旨在最大限度地提高面积探测器强度数据准确性的新软件之后，面积探测器将被应用于电荷密度研究和其他领域。单晶X射线衍射多年来一直被用来研究有机和无机材料的结构。传统的技术是基于使用X射线管，它发射相对低强度的单色辐射，从而将它们的使用限制在大尺寸晶体和强散射体上。同步加速器发射的X辐射具有连续的波长范围，空间发散小，是偏振的，比传统X射线管发射的辐射要亮得多。这些性质使得可以在更短的时间内和更高的精度确定非常小的晶体的结构，这是到目前为止用传统技术无法做到的。然而，新方法在一定程度上仍处于开发阶段。S在本项目中的研究方向是改进新技术，解决物理和材料科学中的新结晶学问题。***

9317770 Coppens In this project in the Physical Chemistry Program of the Chemistry Division, Prof. P. Coppens of the State University of New York at Buffalo will engage in crystallographic research using the National Synchrotron Light Source at the Brookhaven National Laboratory and also perform experiments using advanced conventional facilities. The research consists of several parts: application of anomalous scattering of X-rays to selectively identify site ocupancy, to determine the oxidation states of atoms in solids and to identify spectroscopic transitions; to study the response of crystals to external perturbations, such as laser-induced molecular excitation; and the analysis of modulated and composite solids, which are aperiodic in at least one direction. Very low temperature single crystal techniques are to be used in the analysis of charge densities in crystals, and in the investigation of the temperature-dependence of the structure of low-dimensional conducting solids. Area detectors are to be applied to charge density studies and other fields after new software development aimed at maximizing accuracy of the area-detector intensity data. X-ray diffraction by single crystals has been used for many years to study the structure of organic and inorganic materials. The conventional techniques are based on the use of x-ray tubes, which emit monochromatic radiation of relatively low intensity, thereby limiting their use to large size crystals and strong scatterers. X-radiation emitted by synchrotrons has a continuous range of wavelengths, a low spatial divergence, is polarized, and is much brighter than the radiation emitted from conventional x-ray tubes. These properties allow the determination of the structures of very small crystals, not heretofore possible with conventional techniques, in a much shorter time and with greater accuracy. The new methods are, however, partly still in the development stage. The research to be done in this project i s directed toward improvement of the new technique and the solution of new crystallographic problems in physics and materials science. ***