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Spectroscopy of positronium: atom control and gravity measurements


"The metastable atomic system Positronium (Ps) can be useful for a wide variety of scientific investigations. These include QED tests via precision spectroscopy, the formation of antihydrogen, the creation of positron-atom bound states and Ps molecules, probes of nano-porous and mesoporous materials, the generation of electron-positron plasmas and even the creation of Bose-Einstein condensed Ps. Moreover, long lived Rydberg states of Ps could provide a way to study antimatter gravity. However, being composed of a particle-antiparticle pair Ps is a short lived entity, and conducting such experiments can be very challenging. Recently the use of positron trapping technology has made it possible to generate high instantaneous positron currents, and thereby perform laser excitation of Ps and observe multipositronic effects (such as Ps-Ps scattering, Ps molecule formation and the self-polarization of a Ps gas via spin exchange quenching). This exciting work is opening the door to many new research areas, and the underlying methodology has yet to be fully refined. This project aims to build upon previous advances in this field of positronium physics by expanding the areas of study via new technological approaches and also via collaboration with other groups that have overlapping interests. In particular efforts will be made to create and manipulate longer lived (Rydberg) states of Ps using techniques that have already been developed for other atoms (especially H and He). This offers the possibility of manipulating or even trapping Ps atoms that will not self-annihilate. This in turn would bring into being a unique source of atoms for spectroscopic investigations and facilitate attempts to perform a measurement of the Ps gravitational free-fall. The latter may offer clues to help explain the apparent lack of antimatter in the Universe, which is currently one of the biggest mysteries in Physics."

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UCL Elizabeth Garrett Anderson Institute for Women’s Health
Gower Street
WC1E 6BT London
United Kingdom
Activity type
Higher or Secondary Education Establishments
EU contribution
€ 100 000
Administrative Contact
Giles Machell (Mr.)