Magnetic merging of ultracold atomic gases of 85Rb and 87Rb

Abstract. We report on the magnetic merging of ultracold atomic gases of 85Rb and 87Rb by the controlled overlap of two initially spatially-separated magnetic traps. We present a detailed analysis of the combined magnetic field potential as the two traps are brought together which predicts a clear optimum trajectory for the merging. We verify this prediction experimentally using 85Rb and find that the final atom number in the merged trap is maximised with minimal heating by following the predicted optimum trajectory. Using the magnetic merging approach allows us to create variable ratio isotopic Rb mixtures with a single laser cooling setup by simply storing one isotope in a magnetic trap before jumping the laser frequencies to the transitions necessary to laser cool the second isotope. This offers a simple and cost effective way to achieve suitable starting conditions for sympathetic cooling of 85Rb by 87Rb towards quantum degeneracy. † These authors have contributed equally to this work. a