Collisional Properties of Ultracold K-Rb Mixtures

Abstract

We determine the interspecies s-wave triplet scattering length a(3) for all K-Rb isotopic mixtures by measuring the elastic cross section for collisions between 41K and 87Rb in different temperature regimes. The positive value a(3)=+163(+57)(-12)a(0) ensures the stability against collapse of binary (41)K- (87)Rb Bose-Einstein condensates. For the fermion-boson mixture (40)K- (87)Rb, we obtain a large and negative scattering length which implies an efficient sympathetic cooling of the fermionic species down to the degenerate regime.