Cold collisions in a high-gradient magneto-optical trap

We present a detailed analysis of the cold collision measurements performed in a high-gradient magneto-optical trap with a few trapped Cs atoms first presented in Ueberholz et al (J. Phys. B: At. Mol. Opt. Phys. 33 (2000) L135). The ability to observe individual loss events allows us to identify two-body collisions that lead to the escape of only one of the colliding atoms (up to 10% of all collisional losses). Possible origins of these events are discussed here. We also observed strong modifications of the total loss rate with variations in the repumping laser intensity. This is explained by a simple semiclassical model based on optical suppression of hyperfine-changing collisions between ground-state atoms.