Interaction of Low-energy Positrons with Atoms and Molecules

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This project focuses on experimental studies of the interaction of low-energy positrons with atoms and molecules using a high-resolution, trap-based positron beam and specially designed techniques to study scattering and annihilation processes. Recent theoretical and experimental results provide new topics for study, including understanding the nature of the orders-of-magnitude enhancements of positron annihilation on molecules that is mediated by vibrational Feshbach resonances. Key objectives of the research include understanding the nature of these resonances and the associated phenomena of positron binding to molecules and intramolecular vibrational energy redistribution. Other research topics include studies of resonance and threshold effects in positron scattering and studies of new targets including carbon-60 and metal atoms. In the broader view, the work seeks to establish aspects of a quantitative chemistry of matter and antimatter.The work can be expected to aid in enabling technological applications of low energy positrons, such as developing new methods to ionize large molecules and a new generation of positron beam sources for the characterization of materials. While focusing on research in atomic physics involving antimatter, this project also has impacts in other areas. It involves graduate student and post-doctoral researchers at all levels from the planning of experiments to the dissemination of research results. The project involves small-scale experiments that are an excellent training ground for scientific and technical personnel. The work is communicated broadly, not only to physics audiences but also to those involved in plasma, chemical, and materials science, and gaseous electronics research.