Ultracold paramagnetic and polar diatomic molecules are among the promising systems for quantum simulation of lattice-spin models. Unfortunately, their experimental observation is still challenging. Based on our recent ab initio calculations, we analyze the feasibility of all-optical schemes for the formation of ultracold ${}^{87}\mathrm{Rb}{}^{84}\mathrm{Sr}$ bosonic molecules. A first possibility is photoassociation followed by spontaneous emission. The photoassociation rate coefficients toward electronic states converging to the ${}^{87}\mathrm{Rb}\left(5s{}^{2}S_{1/2}\right)+{}^{84}\mathrm{Sr}(5s5p{}^{3}P_{0,1,2}$) asymptotes are particularly small for vibrational levels close to the asymptote. The creation of molecules would be more interesting by using deeply bound levels which preferentially relax to the $v^{\prime \prime }=0$ level of the ground state. On the other hand, the photoassociation rate coefficients toward electronic states correlated to the $\mathrm{Rb}\left(5p{}^{2}P_{1/2,3/2}\right)+\mathrm{Sr}(5s^2{}^{1}S_0$) are significant for levels close to the asymptote. The spontaneous emission thus creates weakly bound molecules in a single vibrational level. A second option relies on stimulated Raman adiabatic passage implemented in a tight optical trap. It efficiently creates weakly bound ground-state molecules in a well-defined level, thus providing a promising alternative to magnetic Feshbach resonances for further population transfer toward the absolute ground state of the RbSr molecule.

• Received 27 June 2018

DOI:https://doi.org/10.1103/PhysRevA.98.053411