Efficient conversion of closed-channel-dominated Feshbach molecules of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mmultiscripts><mml:mi>Na</mml:mi><mml:mprescripts/><mml:none/><mml:mn>23</mml:mn></mml:mmultiscripts><mml:mmultiscripts><mml:mi mathvariant="normal">K</mml:mi><mml:mprescripts/><mml:none/><mml:mn>40</mml:mn></mml:mmultiscripts></mml:mrow></mml:math> to their absolute ground state
Roman Bause, Akira Kamijo, Xing-Yan Chen, Marcel Duda, Andreas Schindewolf, Immanuel Bloch, Xinyu Luo
Abstract
We demonstrate the transfer of $^{23}\mathrm{Na}^{40}\mathrm{K}$ 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 78.3 G. 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 $|{c}^{3}{\mathrm{\ensuremath{\Sigma}}}^{+},\phantom{\rule{0.16em}{0ex}}v=35,\phantom{\rule{0.16em}{0ex}}J=1\ensuremath{\rangle}\ensuremath{\sim}|{B}^{1}\mathrm{\ensuremath{\Pi}},\phantom{\rule{0.16em}{0ex}}v=12,\phantom{\rule{0.16em}{0ex}}J=1\ensuremath{\rangle}$. 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.