Observation of Heteronuclear Feshbach Molecules from a $^{85}$Rb - $^{87}$Rb gas

TL;DR

This paper reports the creation and observation of heteronuclear Feshbach molecules from a mixture of ultracold $^{85}$Rb and $^{87}$Rb gases, highlighting efficient molecule formation via interspecies resonances and direct binding energy measurements.

Contribution

It demonstrates the first observation of heteronuclear Feshbach molecules from $^{85}$Rb and $^{87}$Rb, utilizing previously unobserved interspecies resonances and comparing different magnetic-field widths.

Findings

Up to 25,000 molecules created.

High conversion efficiency despite non-degenerate $^{85}$Rb.

Measured small binding energies of molecules.

Abstract

We report on the observation of ultracold heteronuclear Feshbach molecules. Starting with a $^{87}$Rb BEC and a cold atomic gas of $^{85}$Rb, we utilize previously unobserved interspecies Feshbach resonances to create up to 25,000 molecules. Even though the $^{85}$Rb gas is non-degenerate we observe a large molecular conversion efficiency due to the presence of a quantum degenerate $^{87}$Rb gas; this represents a key feature of our system. We compare the molecule creation at two different Feshbach resonances with different magnetic-field widths. The two Feshbach resonances are located at $265.44\pm0.15$ G and $372.4\pm1.3$ G. We also directly measure the small binding energy of the molecules through resonant magnetic-field association.