NMR Studies of Extreme Quantum Solids

* 技术摘要 * 核磁共振（NMR）技术将用于探索系统中量子固体和流体的动力学，在这些系统中，在低温下观察到了引人注目的新现象。这些系统包括固体4He在0.1至0.5 K的范围内，其中一个大的意想不到的量子塑性已被报道，和原子簇（3He，HD，H2）局限于内部的纳米结构，增强的量子效应发生在受限的几何形状。由于束缚维数小于布罗意波长，后者将表现出新的热力学特征，能态将完全量子化。在这两种情况下，新的高灵敏度的固态核磁共振技术将开发研究这些系统的微观动力学的非侵入性。这些研究将确定量子塑性对固体4He中3He杂质隧穿的影响，以及被困在纳米多孔材料中的原子纳米团簇的量子化性质，这些纳米多孔材料有望提高储氢能力。该项目将支持对一名博士生进行核磁共振技术设计和应用方面的培训，以便在极端条件下观察来自极低密度原子和分子的信号。这些技术将是重要的一些应用在工业中，如地质勘探和调查结构材料中的缺陷。 * 非技术摘要 * 原子和分子的基本微观运动受量子力学定律支配，虽然量子力学的一般原理已在许多实验室实验中得到验证，但对于最简单的材料，在密度和温度的极端条件下简单原子的行为尚未得到充分探索，例如由轻原子和分子（例如氦和氢）组成的弱相互作用量子流体和固体。组成原子的动力学是由描述原子的波函数决定的，用最简单的术语来说，原子的波函数重叠，因此原子可以交换位置。由于这种独特的量子力学方面，原子可以独立于温度通过晶格结构隧穿。这种隧穿运动将被用来探测固体氦的微观动力学，在低温下非常纯的晶体的弹性特性中已经观察到了大的异常。该项目将使用磁共振技术对这些量子固体中的原子运动进行非侵入性测量，使用的方法类似于但不完全相同于医学应用中的磁共振成像。 参与该项目的学生和合作者将设计实验所需的新磁共振技术，新技术的应用将对地质勘探和结构材料调查等工业应用感兴趣。

****Technical Abstract**** Nuclear magnetic resonance (NMR) techniques will be used to explore the dynamics of quantum solids and fluids in systems where striking new phenomena have been observed at low temperatures. These systems include solid 4He in the range of 0.1 to 0.5 K for which a large unexpected quantum plasticity has been reported, and clusters of atoms (3He, HD, H2) confined to the interior of nanostructures for which enhanced quantum effects occur in the restricted geometries. The latter are predicted to exhibit new thermodynamic features because the confining dimension is less that the De Broglie wavelengths and the energy states will be fully quantized. In both cases new high sensitivity solid state NMR techniques will developed to study the microscopic dynamics of these systems non-invasively. The studies will determine the effect of quantum plasticity on the tunneling of 3He impurities in solid 4He, and the nature of the quantization of nanoclusters of atoms trapped in nanoporous materials that hold promise for improved capabilities of hydrogen storage. The project will support the training of a PhD student in the design and application of NMR techniques for observing signals from very low densities of atoms and molecules in extreme conditions. These techniques will be important for a number of applications in industry such as geological exploration and for investigating defects in structural materials. ****Non-Technical Abstract**** The fundamental microscopic motion of atoms and molecules is governed by the laws of quantum mechanics, and while the general principles of quantum mechanics has been verified in many laboratory experiments, the behavior of simple atoms in extreme conditions of density and temperature has not been fully explored for the simplest materials, such as the weakly interacting quantum fluids and solids comprised of light atoms and molecules such as helium and hydrogen. The dynamics of the constituent atoms is determined by the wave functions describing the atoms and in its most simple terms the wave functions of the atoms overlap and as a result the atoms can exchange places. As a result of this unique quantum mechanical aspect atoms can tunnel through a lattice structure independent of temperature. This tunneling motion will be exploited to probe the microscopic dynamics of solid helium for which large anomalies have been observed in the elastic properties of very pure crystals at low temperatures. The project will use magnetic resonance techniques to carry out non-invasive measurements of the atomic motions in these quantum solids using approaches similar to but not identical to those used in magnetic resonance imaging in medical applications. Students and collaborators working on the project will design new magnetic resonance techniques needed for the experiments and the applications of the new technologies will be of interest to applications in industry such as geological exploration and investigation of structural materials.