Slow Positron Facility

KEK

The World's First Success in Photodetachment of Positronium Negative Ions

Professor Yasuyuki Nagashima of the Department of Physics, Graduate School of Science, Tokyo University of Science and composed of members from the Tokyo University of Science, the High Energy Accelerator Research Organization, the University of Miyazaki and the University of Tokyo, have succeeded for the first time in the world in irradiating a positronium negative ion composed of one positron and two electrons bound together with a laser beam and dividing the ion into an electron and a positronium particle, the latter composed of one electron and one positron still bound together. This technique enables the generation, in an ultra-high vacuum state, of energy-tunable positronium beams at a desired energy level. Positronium beams, having no electric charge, can be used for analyzing insulator surfaces and open the way to a more thorough understanding of the characteristics of positronium itself.

Michishio, et al., Physical Review Letters, 106, 153401 (2011).