Ultracold 88Sr2 molecules in the absolute ground state

We report efficient all-optical creation of an ultracold gas of alkaline-earthmetal dimers, Sr-88(2), in their absolute ground state. Starting with weakly bound singlet molecules formed by narrow-line photoassociation in an optical lattice, followed by stimulated Raman adiabatic passage (STIRAP) via a singlet-dominant channel in the (1)0(u)(+) excited potential, we prepare pure samples of more than 5500 molecules in (XSg+)-S-1 (v = 0, J = 0). We observe two-body collisional loss rates close to the universal limit for both the least bound and most bound vibrational states in (XSg+)-S-1. We demonstrate the enhancement of STIRAP efficiency in a magic-wavelength optical lattice where thermal decoherence is eliminated. Our results pave the way for the use of alkaline-earth-metal dimers for high-precision spectroscopy, and indicate favorable prospects for robust quantum state preparation of ultracold molecules involving closed-shell atoms, as well as molecule assembly in deep optical traps tuned to a magic wavelength.

Automated summary

Efficient all-optical creation of an ultracold gas of alkaline-earth metal dimers, Sr-88(2), in their absolute ground state is achieved. Pure samples of more than 5500 molecules in their absolute ground state are prepared using a combination of narrow-line photoassociation and stimulated Raman adiabatic passage. The results demonstrate enhanced STIRAP efficiency in a magic-wavelength optical lattice, paving the way for high-precision spectroscopy and robust quantum state preparation of ultracold molecules involving closed-shell atoms.