Eur. Phys. J. D 65, 125-131 (2011)
https://doi.org/10.1140/epjd/e2011-10716-1

Regular Article

A high phase-space density mixture of ⁸⁷Rb and ¹³³Cs: towards ultracold heteronuclear molecules

Department of Physics, Durham University, Rochester Building, Science Laboratories, South Road, Durham, DH1 3LE, UK

^b e-mail: s.l.cornish@durham.ac.uk

Received: 21 December 2010
Received in final form: 16 February 2011
Published online: 27 April 2011

Abstract

We report the production of a high phase-space density mixture of ⁸⁷Rb and ¹³³Cs atoms in a levitated crossed optical dipole trap as the first step towards the creation of ultracold RbCs molecules via magneto-association. We present a simple and robust experimental setup designed for the sympathetic cooling of ¹³³Cs via interspecies elastic collisions with ⁸⁷Rb. Working with the  |F = 1,m_F =  +1〉 and the  |3, +3〉 states of ⁸⁷Rb and ¹³³Cs respectively, we measure a high interspecies three-body inelastic collision rate ~10^-25−10^-26 cm⁶   s^-1 which hinders the sympathetic cooling. Nevertheless by careful tailoring of the evaporation we can produce phase-space densities near quantum degeneracy for both species simultaneously. In addition we report the observation of an interspecies Feshbach resonance at 181.7(5) G and demonstrate the creation of Cs₂ molecules via magneto-association on the 4(g)4 resonance at 19.8 G. These results represent important steps towards the creation of ultracold RbCs molecules in our apparatus.