Magnetic Resonance of Metal Hydrides and Transfer of Laser-Generated Polarization

三氢化物（和三氘化物）YH3、LuH3和LaH3中H和D原子的位置和原子运动对于理解这些“可切换镜像”材料的电子绝缘性质很重要。氘核磁共振将用于确定所占据的位置，这在LaDx中尤其重要，因为氘/金属比可以从x=2（金属）连续变化到x=3（绝缘）。核磁共振也将用于寻找镧的细胞间不平等，并研究ZrBe2D1.5在240K时的相变。基于高功率二极管激光的光泵浦技术将用于生产129Xe的升量，核自旋极化高达40%。在典型的电场和温度下，这种极化是热平衡状态下Xe气体的10万倍。目标是设计将自旋极化从129Xe转移到分析感兴趣的自旋，如氢，13C， 15N等的方法。这种转移方法可以彻底改变分析核磁共振的灵敏度，允许检测1微克或更少的样品。许多金属很容易吸收氢，这使得它们在氢燃料储存装置和电池等应用中很有用。在这个项目中，这种金属氢系统的行为的各个方面，“金属氢化物”，将通过核磁共振（NMR）技术的手段进行研究。一个例子是涉及金属钇、镥或镧的金属三氢化物的“可切换镜像”行为。为了在实际设备中利用这种行为，需要更好地理解这种现象的基本原理。金属氢化物的其他性质也将被研究。近年来，使用激光定向氙和氦气的某些同位素的核自旋已经成为可能，从而成为“核自旋极化”。由此产生的核磁共振信号强度提高了10万倍，已经在医学诊断中得到了应用。进一步的应用是通过将自旋极化转移到生物和/或化学分子中原子的核自旋，如碳、氢或氮。本研究旨在探索这种极化转移的可能性。研究生和本科生将参与本研究。他们将因此获得知识和技能，为他们在凝聚态物理和材料科学的前沿领域就业做好准备

The position and atomic motions of H and D atoms in the trihydrides (and trideuterides) YH3, LuH3, and LaH3 are important to understanding the electronically insulating nature of these 'switchable mirror' materials. Deuterium NMR will be used to identify the sites occupied and will be particularly important in LaDx, where the deuterium/metal ratio can be varied continuously from x=2 (metallic) to x=3 (insulating). NMR will also be used to look for cell-to-cell inequivalences in the lanthanum species and to study the phase transition at 240K in ZrBe2D1.5. High power diode laser-based optical pumping techniques will be used to produce 129Xe in liter quantities with nuclear spin polarization up to 40%. This polarization is up to 100,000 times that of Xe gas in thermal equilibrium at typical fields and temperatures. The goal is to devise methods for transferring the spin polarization from 129Xe to spins of analytical interest, such as hydrogen, 13C, 15N, etc. Such transfer methods could revolutionize the sensitivity of analytical NMR, allowing samples of 1 microgram or less to be examined.%%%Many metals absorb hydrogen readily, making them useful for applications such as hydrogen fuel storage devices and batteries. In this project the various aspects of the behavior of such metal hydrogen systems, 'metal hydrides,' will be investigated by means of the nuclear magnetic resonance (NMR) technique. An example is the 'switchable mirror' behavior of the metal trihydrides involving the metal yttrium, lutetium, or lanthanum. The fundamentals of this phenomenon need to be better understood in order to utilize this behavior in practical devices. Other properties of the metal hydrides will also be investigated. In recent years it has become possible to use laser light to orient the nuclear spins of certain isotopes of xenon and helium gases, which thereby have become 'nuclear spin polarized.' The resulting enhancement of NMR signal strength by factors up to 100,000 has already found applications in medical diagnostics. Further applications are envisioned by transferring the spin polarization to the nuclear spins of atoms in molecules of biological and/or chemical interest, such as carbon, hydrogen, or nitrogen. This research is directed to explore the possibilities of such polarization transfer. Graduate and undergraduate students will participate in this research. They will thereby acquire knowledge and skills that will prepare them for employment in forefront areas of condensed matter physics and materials science.***