Coherent Formation of Ground-State Lithium Dimers via Magnetoassociation and STIRAP

We present a coherent assembly scheme for producing ground-state lithium dimers across all stable isotopologues: $^{6}$Li$_2$, $^{7}$Li$_2$, and $^{6}$Li$^{7}$Li. First, we construct optimized adiabatic potentials by refitting threshold data based on spectroscopically accurate Morse/Long-Range (MLR) potentials with correction terms. Using these refined potentials, we characterize the properties of Feshbach resonances in $^{6}$Li$^{7}$Li and identify resonances suitable for molecule formation. Second, we design feasible optical transfer routes to the rovibrational ground state via magnetoassociation followed by a two-step STIRAP sequence, with magnetoassociation pathways tailored to the Feshbach molecule properties of each species. To identify candidate pump and Stokes transitions, we compute transition dipole matrix elements, and the spin character of the Feshbach molecules in each isotopologue. Our results demonstrate that efficient two-leg transfer to both the singlet $X^1\Sigma_g^+$ and triplet $a^3\Sigma_u^+$ ground states is achievable for all lithium isotopologues, offering a practical roadmap for preparing Li$_2$ in absolute ground rovibrational states for controlled ultracold chemistry.