Giant spin relaxation of an ultracold cesium gas.

We have measured the rate of inelastic collisions in a cloud of doubly polarized ground-state cesium atoms ( F=mF=4) confined in a magnetic trap for temperatures T between 8 and 70μK. We find a two-body rate coefficient varying as T−0.63. At 8 μK it reaches 4×10−12cm3s−1 which is 3 orders of magnitude larger than predicted, ruling out a Bose-Einstein condensation of Cs in this internal state