Sympathetic cooling of Rb-85 and Rb-87 - art. no. 021402

We demonstrate sympathetic cooling between magnetically trapped Rb-85 and R b-87 atoms. Up to 6 x 10(6) Rb-85 atoms are cooled via elastic collisions w ith a reservoir of 8 x 10(8) Rb-87 atoms. The temperature of the binary ato mic ensemble is adjusted by using radio-frequency evaporation of Rb-87. Tem peratures as low as T = 100 nK have been realized in the binary ensemble. T hrough a cross-dimensional mixing approach we have been able to measure the interspecies Rb-87-Rb-85 scattering cross section sigma = 1.52(34) x 10(-1 5) m(2).