Eur. Phys. J. D 6, 127-131 (1999)
https://doi.org/10.1007/s100530050292

Experimental study of Velocity Changing Collisions on Coherent Population Trapping in sodium

¹ Istituto di Fisica Atomica e Molecolare,Via del Giardino 7, 56127 Pisa - Italy
² INFM Unità di Siena - Dipartimento di Fisica dell'Università di Siena, Via Banchi di Sotto 53100 Siena - Italy
³ Scuola Normale Superiore and INFM, Piazza dei Cavalieri, 56100 Pisa - Italy
⁴ INFM Unità di Pisa - Dipartimento di Fisica dell'Università di Pisa, P.zza Torricelli 2, 56100 Pisa - Italy

Received: 5 October 1998
Revised: 3 December 1998
Published online: 15 April 1999

Abstract

In this paper a detailed experimental study of Coherent Population Trapping (CPT) effect on sodium induced by a dye-laser operating in a three-mode regime is presented and a detailed analysis of the role of velocity changing collisions is made. These collisions show a very small relaxation effect on the dark resonances which are visible even at high pressures. For the first time we demonstrate the persistence of the ground state coherence to pressures up to one atmosphere for a relatively “heavy” buffer gas like argon. The experimental results have been compared with theory and a very good agreement has been obtained. Preliminary results on the effect of Na-N₂ collisions on Coherent Population Trapping are presented.