X-ray Diffraction Physics and Solid State

这一建议由对应于不同研究领域的不同部分组成，在这些部分中，X射线衍射被用于研究固体物理的基本问题。他们建议对硅进行激光退火研究，并使用掠入射技术结合时间分辨计数来观察熔化过程中布拉格反射的消失。这项工作实际上正在进行中。他们还希望确定液体的径向分布函数，并观察激光照射时的光致伸缩效应，这是由于高密度的电子-空穴对造成的晶格收缩。用穆斯堡尔衍射技术研究了蓝色青铜晶体中滑动电荷密度波(CDW)的产生机制。对晶态氦的性质也进行了实验研究。将进行固态氦电子密度的衍射研究，并将利用同步辐射束的白束形貌术来研究结构缺陷。一个利用多重布拉格散射解决衍射中的位相问题的项目已经完成，该项目得到了美国国家科学基金会先前拨款的支持。由于它代表了衍射物理的一项重大突破，因此在本提案的一节中给出了完整的报告。

This proposal consists of different sections corresponding to different research areas in which x-ray diffraction is used to investigate basic problems of solid state physics. They propose perform a laser annealing study of silicon, and observe the disappearance of Bragg reflection during melting using a grazing incidence technique in conjunction with time resolved counting. This work is actually in progress. They also hope to determine the radial distribution function of the liquid phase, and to observe the photostriction effect, a lattice contraction during laser illumination due to high density of electron-hole pairs. The mechanisms of sliding Charge Density Waves (CDW's) in a blue bronze crystal will be investigated using a Mossbauer diffraction technique. An experimental investigation on the properties of crystalline Helium is also proposed. Diffraction studies of the electron density of He in the solid state will be carried out, and structural defects will be investigated by means of white beam topography using a synchrotron radiation beam. A project on use of multiple Bragg scattering for solving the phase problem in diffraction, supported by a previous NSF grant, has been brought to completion. Since it represents a major breakthrough in diffraction physics, a full report is given in one section of this proposal.