Efficient conversion of closed-channel dominated Feshbach molecules of ${}^{23}$Na${}^{40}$K to their absolute ground state

Abstract

We demonstrate the transfer of ${}^{23}$Na${}^{40}$K molecules from a closed-channel dominated Feshbach-molecule state to the absolute ground state. The Feshbach molecules are initially created from a gas of sodium and potassium atoms via adiabatic ramping over a Feshbach resonance at 78.3G. The molecules are then transferred to the absolute ground state using stimulated Raman adiabatic passage with an intermediate state in the spin-orbit-coupled complex $|c^3{\Sigma }^{+},v=35,J=1⟩\sim |B^1\Pi ,v=12,J=1⟩$. Our measurements show that the pump transition dipole moment linearly increases with the closed-channel fraction. Thus, the pump-beam intensity can be two orders of magnitude lower than is necessary with open-channel dominated Feshbach molecules. We also demonstrate that the phase noise of the Raman lasers can be reduced by filter cavities, significantly improving the transfer efficiency.

8 pages, 7 figures

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