Studies of Atomic Hydrogen Contained in Solid Molecular Hydrogen Isotopes

非技术摘要玻色爱因斯坦凝聚的量子力学现象导致了许多引人入胜和重要的效应。在4He中，它导致了一种超流体，在那里液体可以以粘性流动并无损失地传递热量。在一些金属中，它导致超导，电流在没有损耗的情况下传输--为电力分配提供了潜力，而不会像目前的输电线那样产生损耗。在过冷的原子中也观察到了BEC，这可能导致为全球定位系统提供动力的更精确的原子钟。其他尚未被发现的系统可能会表现出同样令人着迷和重要的行为。在这个项目中，我们将尝试在嵌入固体分子氢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摄氏度以下)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方面的培训，这些技术与许多物理领域有关，如量子计算。正在推行积极的外展计划。继续与研究生见面、大专学生参观和参加科学博览会。例如，首席研究员在德克萨斯农工物理与工程节上进行了公开演讲，并进行了演示。这个节日通常有5000多名来自德克萨斯州和其他州的学生参加。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2 mm波强磁场(4.6特斯拉，共振频率130 GHz)中的性质。用于这些测量的分光计已完全运行。一台稀释冰箱现已就位，可将样品冷却至100MK以下。为了达到完全的玻色-爱因斯坦凝聚，我们研究了原子核自旋的偏振偏离玻尔兹曼分布的情况，并将其降低到较低的温度和较高的氢原子浓度。尽管在以前的实验中发现自旋-晶格弛豫只有几个小时，但不可能完全饱和两个最低超精细态之间的跃迁。这一异常行为得到了充分的调查。还进行了磁场梯度下的烧孔实验，以确定发生玻色-爱因斯坦凝聚时氢原子的迁移率。最后，研究了不同衬底对氢原子偏离玻尔兹曼统计的影响。

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.