Neutron Scattering Studies of Quantum Systems

9624762 Sokol本课题将开展量子系统的中子散射研究。量子液体和固体（如氦和氢）的凝聚相的行为受量子和统计效应的支配，这些效应导致了许多独特的性质，如超流动性。最近，这些系统在受限几何中的约束表明，其性质可能与体有很大不同。弹性和非弹性中子散射将用于探测这些相的微观结构和动力学。这项工作将集中在氦同位素（3He和4He），同位素混合物（3He-4He）和氢（H2），其中凝聚态的性质由量子效应主导。弹性和总中子散射测量将提供空间相关的信息。非弹性中子散射测量将用于研究扩散运动、集体激发和单体密度矩阵。(动量分布)。测量将在散装系统和受限几何形状的液体和固体中进行，如多孔Vycor玻璃、气凝胶和溶胶以及沸石。本研究项目将进行量子系统的中子散射研究。待研究的量子固体和液体，如氦和氢，为研究金属、超导体和磁性材料中的许多量子效应提供了一个有用的模型系统。然而，它们没有同样的材料制备问题，因此更容易提取中心物理原理。弹性和非弹性中子散射将用于探测这些固、液相的微观结构和动力学。这些测量将提供氦原子和氢分子在凝聚态中的静态和动态相互作用的信息。这项工作将集中在氦同位素（3He和4He）、同位素混合物（3He- 4He）和氢（H2）的体相和受限几何。＊＊＊

9624762 Sokol Neutron scattering studies of quantum systems will be carried out in this research project. The behavior of the condensed phases of quantum liquids and solids, such as helium and hydrogen, are dominated by quantum and statistical effects which are responsible for many unique properties such as superfluidity. More recently, confinement of these systems in restricted geometries has shown that the properties can be substantially different from the bulk. Elastic and inelastic neutron scattering will be used to probe the microscopic structure and dynamics of these phases. This work will focus on the helium isotopes (3He and 4He), isotopic mixtures (3He-4He), and hydrogen (H2) where the properties of the condensed phase are dominated by quantum effects. Elastic and total neutron scattering measurements will provide information on the spatial correlation's. Inelastic neutron scattering measurements will be used to study diffusive motion, collective excitations, and the one-body density matrix. (momentum distribution). Measurements will be carried out in both bulk systems and for liquids and solids in confined geometries such as porous Vycor glass, aerogels and solgels, and zeolites. %%% Neutron scattering studies of quantum systems will be carried out in this research project. Quantum solids and liquids, such as helium and hydrogen to be studied, provide a useful model system for studying many of the quantum effects that are found in metals, superconductors, and magnetic materials. However, they do not suffer the same materials preparation problems so that the central physical principles are more easily extracted. Elastic and inelastic neutron scattering will be used to probe the microscopic structure and dynamics of these solid and liquid phases. These measurements will provide information on the static and dy namic interaction of helium atoms and hydrogen molecules in the condensed phases. This work will focus on the helium isotopes (3He and 4He), isotopic mixtures (3He- 4He), and hydrogen (H2) in both the bulk phases and in confined geometries. ***