Characterization of Feshbach resonances in ${}^6\mathrm{L}\mathrm{i}{-}^7\mathrm{L}\mathrm{i}$ using improved interaction potentials

We characterize Feshbach resonances in all isotopologues of the $\mathrm{L}\mathrm{i}-\mathrm{L}\mathrm{i}$ system with improved interaction potentials. Starting from spectroscopically accurate Morse/long-range (MLR) potential-energy curves for the singlet ($X^1{\mathrm{\Sigma }}^{+}$) and triplet ($a^3{\mathrm{\Sigma }}^{+}$) electronic states of ${\mathrm{L}\mathrm{i}}_2$, 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 ${}^6\mathrm{L}\mathrm{i}{-}^6\mathrm{L}\mathrm{i}$ and ${}^7\mathrm{L}\mathrm{i}{-}^7\mathrm{L}\mathrm{i}$ 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 ${}^6\mathrm{L}\mathrm{i}{-}^7\mathrm{L}\mathrm{i}$ 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 ${\mathrm{L}\mathrm{i}}_2$ molecules in deeply bound rovibrational levels of both the $X^1{\mathrm{\Sigma }}^{+}$ and $a^3{\mathrm{\Sigma }}^{+}$ potentials across all three isotopologues.