Structure of the Interfacial Properties of Helium-3, Helium-4, and Helium-3/Helium-4 Mixtures: X-ray Scattering Studies

Helium-3、Helium-4 和 Helium-3/Helium-4 混合物的界面性质结构：X 射线散射研究

• 批准号: 9523281
• 负责人: Peter Pershan
• 金额: $ 19.5万
• 依托单位: Harvard University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-07-01 至 1999-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9523281&HistoricalAwards=false
• 关键词: Structure; Interfacial; Properties; Helium; Mixtures

9523281 Pershan This project employs x-ray scattering methods to measure the interfacial structures of 3He, 4He and 3He - 4He mixtures over a range of temperatures and composition, and under a variety of externally controlled geometries. The helium interfaces are interesting from a theoretical view because they represent the relatively rare realization of a well-defined, macroscopically oriented, inhomogeneous quantum fluid. The superfluid properties of bulk helium are fundamentally dependent on the liquid density. However, it is extremely difficult to vary the bulk density by significant fraction. In contrast, the density across the liquid/vapor interface varies from the uniform bulk value to essentially zero. The x-ray experiments are currently the only test of extant theories of the structural changes anticipated for mixture of the quantum fluids. In addition, it may be possible to measure the in-plane correlations for the two-dimensional electron fluid that can be stabilized on the surface of the helium. If successful, this would provide a tool to characterize the structure and positional correlations of the two-dimensional Wigner lattice formed by the layer of electrons trapped in the image potential at the helium surface. The experiments are of fundamental interest and will be of wider interest in the field of surface physics and fluid dynamics. %%% This project employs x-ray scattering methods to measure the interfacial structures of 3He, 4He and 3He - 4He fluid mixtures over a range of temperatures and composition, and under a variety of externally controlled geometries. These cryogenic fluids have many novel properties related to their "superfluidity". The arrangements of atoms forming the surface layers will be determined by x-ray methods using a beam of x-rays from a synchrotron light source. In another sub-project, it is possible to trap a film of e lectrons on the surface of the helium. The arrangement of electrons in this layer will also be sought. The experiments are of fundamental interest and will be of wider interest in the field of surface physics and fluid dynamics. ***

小行星9523281 该项目采用X射线散射方法来测量3 He，4 He和3 He-4 He混合物在一系列温度和组成下的界面结构，并在各种外部控制的几何形状。 从理论上看，氦的界面很有趣，因为它们代表了相对罕见的定义明确的、宏观取向的、非均匀的量子流体。大量氦的超流性质从根本上取决于液体密度。 然而，通过显著的分数改变堆积密度是极其困难的。 相反， 液体/蒸汽界面从均匀的体积值变化到基本为零。X射线实验是目前对量子流体混合物预期结构变化的现存理论的唯一测试。此外，还可以测量 的 平面内的相关性的二维电子流体，可以稳定的表面上的氦。 如果成功的话，这将提供一种工具来表征二维维格纳晶格的结构和位置相关性，所述二维维格纳晶格由被捕获在氦表面的像势中的电子层形成。这些实验具有根本意义，并将在表面物理和流体动力学领域引起更广泛的兴趣。 该项目采用X射线散射方法测量3 He，4 He和3 He-4 He流体混合物在一定温度和成分范围内的界面结构，并在各种外部控制的几何形状下。这些低温流体具有许多与其“超流性”相关的新特性。 形成表面层的原子的排列将 通过使用来自同步加速器光源的X射线束的X射线方法来确定。在另一个子项目中，有可能在氦表面捕获一层电子膜。 也将寻求该层中电子的排列。 这些实验具有根本意义，并将在表面物理和流体动力学领域引起更广泛的兴趣。 ***