TRAP LOSS COLLISIONS OF LI-7 - THE ROLE OF TRAP DEPTH

We present experimental measurements of the rate of loss of ultracold Li-7 from a magnetooptical trap (MOT) produced by collisions between t he trapped atoms. The loss rate was measured for a range of trap laser intensities and detunings. Since fine-structure changing collisions m ay be suppressed as a loss mechanism in Li, it is possible to isolate the loss due to that mechanism from the radiative escape mechanism. Th e measured rates are compared with recent theoretical calculations. Re latively good agreement is found for the magnitude of the loss rate, b ut there is disagreement as to the qualitative dependence on trap lase r detuning and intensity. In many respects, Li is ideal for comparison s of trap loss measurements with theory, since the interatomic potenti als for Li are relatively well known. We also present a realistic calc ulation of trap depth, or equivalently, escape velocity. This fully th ree-dimensional calculation incorporates all relevant atomic levels. W e demonstrate that accurate knowledge of the trap depth is essential f or quantitative comparisons of experimental loss rate measurements wit h theory.