High Resolution Crystallographic Studies Using Synchrotron Radiation

9317770 Coppens在化学部物理化学计划的这一项目中，布法罗的纽约州立大学的P. Coppens教授将在布鲁克海文国家实验室利用国家同步加速器光源进行晶体学研究，并利用先进的常规设备进行实验。 这项研究由几个部分组成：应用X射线的异常散射有选择地确定现场ocuplants，以确定固体中原子的氧化态和确定光谱转换;研究晶体对外部扰动的反应，如激光诱导的分子激发;以及分析调制和复合固体，这是在至少一个方向上的非周期性。 极低温单晶技术将用于分析晶体中的电荷密度，以及研究低维导电固体结构的温度依赖性。 在新的软件开发之后，面积探测器将被应用于电荷密度研究和其他领域，旨在最大限度地提高面积探测器强度数据的准确性。 单晶X射线衍射已被用于研究有机和无机材料的结构多年。 常规技术基于X射线管的使用，X射线管发射相对低强度的单色辐射，从而限制了它们对大尺寸晶体和强散射体的使用。 由同步加速器发射的X射线具有连续的波长范围、低空间发散度、被偏振，并且比从常规X射线管发射的辐射亮得多。 这些性质允许在更短的时间内和更高的精度下确定非常小的晶体的结构，这是迄今为止用常规技术不可能的。 然而，新方法部分仍处于开发阶段。 本项目的研究方向是改进新技术，解决物理学和材料科学中新的晶体学问题。 ***

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. ***