Positronium Laser Cooling via the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mn>1</mml:mn></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msup><mml:mi>S</mml:mi><mml:mtext>−</mml:mtext><mml:msup><mml:mrow><mml:mn>2</mml:mn></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msup><mml:mi>P</mml:mi></mml:mrow></mml:math> Transition with a Broadband Laser Pulse
L. T. Glöggler, Natali Gusakova, B. Rienäcker, A. Camper, R. Caravita, S. Ḣuck, Marco Volponi, T. Wolz, L. Penasa, V. Krumins, F. P. Gustafsson, D. Comparat, M. Auzins, B. Bergmann, Petr Burian, R.S. Brusa, F. Castelli, G. Cerchiari, R. Ciuryło, Giovanni Consolati, M. Doser, L. K. Graczykowski, Małgorzata Grosbart, F. Guatieri, S. Haider, M. A. Janik, G. Kasprowicz, G. Khatri, Łukasz Kłosowski, G. Kornakov, Lidia Lappo, A. Linek, J. Malamant, S. Mariazzi, V. Petráček, Mariusz Piwiński, S. Pospı́šil, L. Povolo, F. Prelz, S. A. Rangwala, T. Rauschendorfer, Bharat Singh Rawat, Volodymyr Rodin, O. Røhne, H. Sandaker, Petr Smolyanskiy, Tomasz Sowiński, D. Tefelski, T. Vafeiadis, Carsten Welsch, M. Zawada, J. Zieliński, N. Zurlo
Abstract
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. We demonstrate a 58(9)% increase in the fraction of Ps atoms with v_{1D}<3.7×10^{4} ms^{-1}.