Strong evaporative cooling of a trapped cesium gas

Using forced radio-frequency evaporation, we have cooled cesium atoms prepared in the sublevel F = -m(F) = 3 and confined in a magnetic trap. At the end of the evaporation ramp, the sample contains ,similar to 7000 atoms at 80 nK, corresponding to a phase space density 3x10(-2). A molecular dynamics approach, including the effect of gravity, gives a good account for the experimental data, assuming a scattering length larger than 300 Angstrom. (C)1998 Optical Society of America