Spectroscopy of Positronium Molecules and Bose-Einstein Condensates

University Of California-Riverside, Riverside CA

Investigators

Abstract

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.