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Feshbach resonances with large background scattering length: interplay with open-channel resonances

B. Marcelis·E. G. M. van Kempen·B. J. Verhaar·S. J. J. M. F. Kokkelmans
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Abstract

Feshbach resonances are commonly described by a single-resonance Feshbach model, and open-channel resonances are not taken into account explicitly. However, an open-channel resonance near threshold limits the range of validity of this model. Such a situation exists when the background scattering length is much larger than the range of the interatomic potential. The open-channel resonance introduces strong threshold effects not included in the single-resonance description. We derive an easy-to-use analytical model that takes into account both the Feshbach resonance and the open-channel resonance. We apply our model to $^{85}$Rb, which has a large background scattering length, and show that the agreement with coupled-channels calculations is excellent. The model can be readily applied to other atomic systems with a large background scattering length, such as $^6$Li and $^{133}$Cs. Our approach provides full insight into the underlying physics of the interplay between open-channel (or potential) resonances and Feshbach resonances.

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B. Marcelis, E. G. M. van Kempen, B. J. Verhaar, S. J. J. M. F. Kokkelmans. 2004-04-29. Feshbach resonances with large background scattering length: interplay with open-channel resonances. https://doi.org/10.1103/physreva.70.012701

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