L T Glöggler, N Gusakova, B Rienäcker, A Camper, R Caravita, S Huck, M Volponi, T Wolz, L Penasa, V Krumins, F P Gustafsson, D Comparat, M Auzins, B Bergmann, P Burian, R S Brusa, F Castelli, G Cerchiari, R Ciuryło, G Consolati, M Doser, Ł Graczykowski, M Grosbart, F Guatieri, S Haider, M A Janik, G Kasprowicz, G Khatri, Ł Kłosowski, G Kornakov, L Lappo, A Linek, J Malamant, S Mariazzi, V Petracek, M Piwiński, S Pospíšil, L Povolo, F Prelz, S A Rangwala, T Rauschendorfer, B S Rawat, V Rodin, O M Røhne, H Sandaker, P Smolyanskiy, T Sowiński, D Tefelski, T Vafeiadis, C P Welsch, M Zawada, J Zielinski, N Zurlo
We report on laser cooling of a large fraction of positronium (Ps) in free flight by strongly saturating the 1^{3}S-2^{3}P transition with a broadband, long-pulsed 243 nm alexandrite laser. The ground state Ps cloud is produced in a magnetic and electric field-free environment. We observe two different laser-induced effects. The first effect is an increase in the number of atoms in the ground state after the time Ps has spent in the long-lived 2^{3}P states. The second effect is one-dimensional Doppler cooling of Ps, reducing the cloud's temperature from 380(20) to 170(20) K...
February 23, 2024: Physical Review Letters