Excited-State Annihilation of Positronium in Cryogenic Silica Aerogel for In-Material Laser Cooling

Résumé fourni par la source

Abstract We report recent progress toward achieving positronium (Ps) Bose–Einstein condensation (BEC) by combining thermalization in nanoporous materials with ultraviolet (UV) laser Doppler cooling. Experiments were performed using silica aerogels held at two distinct thermal conditions—approximately room temperature and cryogenic temperature down to 8 K (measured at the sample-holder)—to study the laser-induced annihilation of Ps atoms excited to the 2P state. Resonant excitation at 243 nm significantly enhanced gamma-ray emission, with the annihilation signal reduced by approximately 50 % at low temperature compared to room temperature. Increasing the delay between Ps formation and laser excitation further reduced the annihilation probability. These observations confirm that Ps thermalization affects 2P-Ps annihilation. The results support a model of surface-induced 2P-state decay and suggest that excited-state Ps serves as a sensitive probe of surface interactions in nanoporous media. This constitutes an important step toward implementing laser cooling of Ps confined in solids—an essential prerequisite for realizing Ps-BEC. Ongoing efforts focus on systematic evaluation of pore structure, surface chemistry, and temperature effects to optimize Ps dynamics toward condensation.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.