Spectroscopy of Positronium Molecules and Bose-Einstein Condensates

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。正电子，化学符号为Ps，是氢原子的一种非常轻的形式，仅由一个电子与一个反电子或正电子结合而成。Ps原子由等量的物质和反物质组成，在湮灭成伽马射线之前，它只能存活不到一微秒。然而，它短暂的存在足以让我们了解有关计量学、化学和物质集体性质的重要知识。加州大学河滨分校（UCR）的科学家们最近发现，含有数百万个Ps原子的密集集合可以形成双正电子分子Ps2，类似于众所周知的氢分子H2。在这个奖项期间，UCR的科学家团队和他们的学生将测量新发现分子的性质，并将组装和研究由Ps原子密集气体形成的第一个玻色-爱因斯坦凝聚体。这些话题之所以引人注目，是因为它们代表了新的反物质物种，它们应该表现出迷人的量子特性，这些特性将通过激光光谱学来测量。正电子的轻质量意味着玻色-爱因斯坦凝聚可以在接近室温的温度下发生，而不是普通物质原子阱通常的极低温度。由于正电子原子是用纯量子电动力学理论完全描述的，因此对玻色-爱因斯坦凝聚态正电子能级的精确测量可以直接与基本常数相关。从长远来看，与这项工作相关的正电子源的发展将对工业材料表征、医学正电子发射断层扫描（PET）的发展以及可能的国防有直接的好处。实现正电子的玻色-爱因斯坦凝聚是制造湮灭伽马射线激光器的先决条件之一，它可能具有重要的技术和军事应用，将促进美国的安全，特别是如果能量大于1兆焦耳最终成为可能。这些实验开辟了跨学科的研究方向，导致与各种机构的合作，并加强了UCR的教育项目。制造包含Ps原子的精细微结构需要应用硅技术，如电子束光刻。精密测量需要与国家标准与技术研究所的时间和频率部门合作。正电子技术的进一步发展是与一家名为First Point Scientific Inc.的小型企业的科学家合作完成的，这为学生提供了一个了解科学研究的小型企业方面的机会。该项目将利用有趣的反物质概念来解决吸引代表性不足的少数民族和妇女参与科学研究的问题，以帮助吸引背景广泛的学生参与科学探索。这项研究将通过网络发表在高影响力的期刊上，以确保研究结果的广泛传播，并为广大读者提供研究成果。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Positronium, with the chemical symbol Ps, is a very light form of hydrogen atom consisting only of an electron bound to an anti-electron or positron. Being composed of equal amounts of matter and antimatter, the Ps atom lives for only a fraction of a microsecond before annihilating into gamma rays. Nevertheless, its ephemeral existence is long enough for us to learn important things about metrology, chemistry, and the collective properties of matter. Scientists at the University of California, Riverside (UCR) have recently found that dense collections containing millions of Ps atoms can make di-positronium molecules Ps2 in analogy with the well known hydrogen molecules H2. In the period of this award, the team of UCR scientists and their students will measure the properties of the newly discovered molecules and will assemble and study the first Bose-Einstein condensates formed from a dense gas of Ps atoms. These topics are of compelling interest because they represent new species of antimatter that should exhibit fascinating quantum properties that will be measured via laser spectroscopy. The light mass of positronium means that Bose-Einstein condensation can occur at near room temperature compared to the usual extremely low temperatures of ordinary matter atom traps. Because the positronium atom is fully described in terms of pure quantum electrodynamics theory, precision measurements on the positronium energy levels in the Bose-Einstein condensed state can be directly related to the fundamental constants.In the long term, positron source developments associated with this work will have direct benefits to industry for materials characterization, to medicine for developments in positron emission tomography (PET), and possibly to defense. Achieving a Bose-Einstein condensate of positronium is one of the prerequisites for making an annihilation gamma ray laser which could have significant technological and military applications that would promote the security of the United States, particularly if energies greater than 1 MJ eventually become feasible. The experiments are opening up interdisciplinary aspects of the research, leading to partnering with a variety of institutions and enhancing the educational program at UCR. The fabrication of elaborate microstructures for containing Ps atoms requires applications of silicon technologies such as electron beam lithography. Precision measurements require collaborations with The Time and Frequency Division at the National Institute of Standards and Technology. Further developments of positron technologies are being done in collaboration with scientists from a small business, First Point Scientific Inc., providing a chance for students to learn about the small business side of scientific research. The project will address the problem of attracting underrepresented minorities and women to science using the intriguing concept of antimatter to help attract students from a wide background to the pipeline of scientific inquiry. The research will be published in high impact journals via the web to insure the wide dissemination of the results and its availability to a large audience.