The capture process in spherical magneto-optical traps: experiment and 1D magnetic field models

The influence of the magnetic field gradient on the number of Cs atoms captured in a three-dimensional magneto-optical trap is investigated both theoretically and experimentally. Two one-dimensional models of the capture process are proposed, which differ only by the nature of the assumptions on the effect of Zeeman optical pumping. Transverse cooling beams are accounted for by a mere modification of the scattering rate. Comparison with experiment shows that the number of trapped atoms versus laser detuning, laser intensity, laser beam diameter and magnetic field gradient is best predicted by a model including all Zeeman substates of the Cs atoms. Quantitative agreement is within a factor of three in most cases of interest.