Collisional stability of double bose condensates

This paper presents quantitative calculations of collisional loss rates for pure Na-23 or Rb-87 atoms in a binary mixture of hyperfine states \F, M]. We find that the recent observation of a dual Bose condensate consisting of Rb-87 \1, -1] and \2, 2] atoms is unique and will not occur in Na. We attribute this to the unexpectedly small inelastic spin-exchange rate associated with Rb-87 s-wave hyperfine collisions. This fortuitous result arises from nearly equal (5.45 +/- 0.26 nm) scattering lengths for two colliding Rb-87 atoms in their \1, -1] or \2, 2] states.