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arXiv:2603.02361 · Physical Review A

Characterization of Feshbach resonances in a Li 6 − Li 7 mixture using improved interaction potentials

Jing-Chen Zhang, Paul S. Julienne, Yu Liu

Published May 12, 2026• 1 citation
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Abstract

We characterize Feshbach resonances in all isotopologues of the $\mathrm{Li}{-}\mathrm{Li}$ system with improved interaction potentials. Starting from spectroscopically accurate Morse/long-range (MLR) potential-energy curves for the singlet ($X^{1}Σ^{+}$) and triplet ($a^{3}Σ^{+}$) electronic states of $\mathrm{Li}_2$, we apply small phenomenological inner-wall adjustments (following Julienne and Hutson, Phys. Rev. A 89, 052715 (2014), arXiv:1404.2623v3) and fit the resulting potentials to threshold measurements for the $^{6}\mathrm{Li}{-}^{6}\mathrm{Li}$ and $^{7}\mathrm{Li}{-}^{7}\mathrm{Li}$ isotopologues, including binding energies, scattering lengths, and Feshbach resonance positions. Using the optimized potentials in coupled-channels scattering calculations, we predict and characterize s-wave Feshbach resonances in the $^{6}\mathrm{Li}{-}^{7}\mathrm{Li}$ isotopologue. In its lowest-energy hyperfine channel, all resonances are narrow ($\sim 0.01{-}0.1$ G), strongly closed-channel dominated, and predominantly triplet in electronic spin character, in marked contrast to the homonuclear systems. These results provide a foundation for designing Raman optical-transfer pathways to produce ultracold $\mathrm{Li}_2$ molecules in deeply bound rovibrational levels of both the $X^1Σ^{+}$ and $a^3Σ^{+}$ potentials across all three isotopologues.

DOI
10.1103/p3bm-rpcb

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We report a theoretical study of Feshbach resonances in 6Li+23Na^{6}\mathrm{Li}+^{23}\mathrm{Na}6Li+23Na and 7Li+23Na^{7}\mathrm{Li}+^{23}\mathrm{Na}7Li+23Na mixtures at ultracold temperatures using accurate interaction potentials in a full quantum coupled-channel calculation. Feshbach resonances for l=0l=0l=0 in the initial collisional open channel 6Li(f=1∕2,mf=1∕2)+23Na(f=1,mf=1)^{6}\mathrm{Li}(f=1∕2,{m}_{f}=1∕2)+^{23}\mathrm{Na}(f=1,{m}_{f}=1)6Li(f=1∕2,mf​=1∕2)+23Na(f=1,mf​=1) are found to agree with previous measurements, leading to precise values of the singlet and triplet scattering lengths for the 6,7Li+23Na^{6,7}\mathrm{Li}+^{23}\mathrm{Na}6,7Li+23Na pairs. We also predict additional Feshbach resonances within experimentally attainable magnetic fields for other collision channels.
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