Studies of Atomic Hydrogen Contained in Solid Molecular Hydrogen Isotopes

玻色-爱因斯坦凝聚的量子力学现象导致了许多引人入胜的重要效应。在4He中，它导致了一种超流体，在这种超流体中，液体可以有粘度地流动，并且可以毫无损失地传递热量。在某些金属中，它会导致超导性，在这种情况下电流可以无损耗地传输，从而提供了一种潜在的配电方式，而不会像目前的输电线那样产生损耗。BEC也在超冷原子中被观察到，这可能导致更精确的原子钟，为全球定位系统提供动力。其他尚未被发现的系统，可能表现出同样迷人和重要的行为。在这个项目中，我们将尝试在嵌入固体氢分子的氢原子中产生玻色爱因斯坦凝聚体。这些研究将在超低温（绝对零度以上0.1度以下）下进行，并利用微波磁共振技术。这项工作将提供最先进的低温和微波技术的培训，这些技术与量子计算等许多物理领域相关。积极推行外展计划。与研究生的会面、大专学生的参观和科学展览的参与仍在继续。例如，首席研究员在德州农工大学物理与工程节上发表公开演讲并进行演示。这个节日通常会有来自德克萨斯州和其他州的5000多名学生参加。技术摘要：利用电子自旋共振技术，研究了嵌入固体分子氢膜中的氢原子在对应于2mm波的高磁场（4.6 Tesla，共振频率130 GHz）下的性质。用于这些测量的光谱仪是完全可操作的。现在有一台稀释制冷机，可以将样品冷却到100 mK以下。在较低的温度和较高的氢原子浓度下，为了达到完全的玻色-爱因斯坦凝聚，研究了先前观察到的核自旋极化与玻尔兹曼分布的巨大偏离。虽然在先前的实验中发现自旋-晶格弛豫持续了几个小时，但不可能完全饱和两个最低超精细态之间的跃迁。对这种异常行为进行了充分的调查。在磁场梯度下进行了空穴燃烧实验，以确定玻色-爱因斯坦凝聚发生时氢原子的迁移率。最后，研究了不同薄膜衬底对氢原子偏离玻尔兹曼统计量的影响。

Non-technical AbstractThe quantum mechanical phenomena of Bose Einstein Condensation leads to many fascinating and important effects. In 4He it leads to a superfluid where the liquid can flow with viscosity and transport heat without loss. In some metals it leads to superconductivity where electric currents are carried without loss - offering the potential for power distribution without the losses that occur in current power lines. BEC has also been observed in super-cooled atoms which could lead to more precise atomic clocks that power the global positioning system. Other, yet to be discovered systems, may show equally fascinating and important behavior. In this project we will attempt to produce a Bose Einstein Condensate in hydrogen atoms embedded in solid molecular hydrogen. The studies will take place at ultra-low temperature (below 0.1 degrees above absolute zero) and utilize microwave magnetic resonance techniques. This work will provide training in state-of-the-art low temperature and microwave techniques which are relevant in many areas of physics such as quantum computing. An active outreach program is pursued. Meetings with graduate students, visits by junior college students and participation in science fairs continues. For example, the principal investigator gives public lectures at the Texas A & M Physics and Engineering Festival with demonstrations. The festival is typically attended by more than 5000 students from all over the state of Texas and beyond. Technical AbstractThe properties of hydrogen atoms embedded in solid molecular hydrogen films are studied by electron spin resonance in a high magnetic field (4.6 Tesla, resonant frequency 130 GHz) corresponding to 2mm waves. The spectrometer for these measurements is fully operational. A dilution refrigerator is now in place to cool the samples to temperatures below 100 mK. The large departure of the polarization of the nuclear spins from the Boltzmann distribution observed previously are investigated down to lower temperatures and at higher hydrogen atom concentrations in an attempt to reach full Bose-Einstein condensation. Although in previous experiments the spin-lattice relaxation was found to be several hours, it was not possible to fully saturate the transition between the two lowest hyperfine states. This anomalous behavior is fully investigated. Hole burning experiments in a magnetic field gradient also are performed to determine the hydrogen atom mobility as Bose-Einstein condensation occurs. Finally, the effect of different film substrates on the departure from Boltzmann statistics of hydrogen atoms are studied.