Proposal for the formation of ultracold deeply bound RbSr dipolar molecules by all-optical methods

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
87Rb84Sr bosonic molecules. A first possibility is photoassociation followed by spontaneous emission. The
photoassociation rate coefficients toward electronic states converging to the 87Rb(5s 2S1/2 ) + 84Sr(5s5p 3P0,1,2)
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
= 0 level of the
ground state. On the other hand, the photoassociation rate coefficients toward electronic states correlated to
the Rb(5p 2P1/2,3/2 ) + Sr(5s2 1S0) 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.