Feshbach Resonances in Rubidium 87: Precision Measurement and Analysis

More than 40 Feshbach resonances in rubidium 87 are observed in the magnetic-field range between 0.5 and 1260 G for various spin mixtures in the lower hyperfine ground state. The Feshbach resonances are observed by monitoring the atom loss, and their positions are determined with an accuracy of 30 mG. In a detailed analysis, the resonances are identified and an improved set of model parameters for the rubidium interatomic potential is deduced. The elastic width of the broadest resonance at 1007 G is predicted to be significantly larger than the magnetic-field resolution of the apparatus. This demonstrates the potential for applications based on tuning the scattering length.

Figure 1

$l=0$ Feshbach resonances in a coupled-channel calculation. Bound-state energies (solid lines) are shown as a function of magnetic field with quantum numbers $(f_1,f_2)v^{\prime }$ assigned at $B=0$. Additionally, dissociation threshold energies (dotted lines) are shown for four different entrance channels $(m_{f1}^{\mathrm{i}\mathrm{n}},m_{f2}^{\mathrm{i}\mathrm{n}})$. A Feshbach resonance ($•$) occurs, when a bound state with quantum number $m_F$ crosses a dissociation threshold with the same $m_F$.

Figure 2

Shape of the broadest Feshbach resonance. The number of atoms ($\circ$) remaining in the trap after a 50-ms hold time is displayed as a function of magnetic field. The three-body loss rate coefficient $K_3$ is also shown ($•$).