We report on the creation of ultracold 84Sr2 molecules in the electronic ground state. The molecules are formed from atom pairs on sites of an optical lattice using stimulated Raman adiabatic passage (STIRAP). We achieve a transfer efficiency of 30% and obtain 4×104 molecules with full control over the external and internal quantum state. Our work overcomes the previous limitation of STIRAP schemes to systems with magnetic Feshbach resonances, thereby establishing a route that is applicable to many systems beyond alkali-metal dimers.
We plan to create RbSr ground-state molecules, which are open-shell polar molecules with an electric dipole moment of 1.5 Debye. As a first step towards this goal, we have produced a Rb/Sr double BEC. A striking aspect of our production method is the efficient cooling of Rb by Sr atoms, which are laser cooled on a narrow intercombination line. This powerful technique allows us to cool the mixture to 1 μK, reaching a phase-space density of 0.07 for Sr and 0.015 for Rb in an optical trap. Evaporative cooling from such favorable starting conditions leads to simultaneous Bose-Einstein condensation of both species with 1.5x105 atoms in each cloud. Association of RbSr molecules will either be performed using magnetic Feshbach resonances, or, in case those resonances are too narrow, using the method we developed for the creation of Sr2 molecules.
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