Resonant Magnetic Field Control of Elastic Scattering in ColdR85b

Abstract

A magnetic field-dependent Feshbach resonance has been observed in the elastic scattering collision rate between atoms in the $F=2,M=-2\mathrm{}$ state of ${}^{85}\mathrm{Rb}$. Changing the magnetic field by several Gauss caused the collision rate to vary by a factor of 1$0^4$, and the sign of the scattering length could be reversed. The resonance peak is at 155.2(4) G and its width is 11.6(5) G. From these results we extract much improved values for the three quantities that characterize the interaction potential: The van der Waals coefficient $C_6$, the singlet scattering length $a_S$, and the triplet scattering length $a_T$.