A pathway to ultracold bosonic 23Na39K ground state molecules

Abstract

We spectroscopically investigate a pathway for the conversion of ^23 Na ^39 K Feshbach molecules into rovibronic ground state molecules via stimulated Raman adiabatic passage. Using photoassociation spectroscopy from the diatomic scattering threshold in the a ^3 Σ ^+ potential, we locate the resonantly mixed electronically excited intermediate states $| {B}^{1}{\rm{\Pi }},v=8\rangle $ and $| {c}^{3}{{\rm{\Sigma }}}^{+},v=30\rangle $ which, due to their singlet–triplet admixture, serve as an ideal bridge between predominantly a ^3 Σ ^+ Feshbach molecules and pure X ^1 Σ ^+ ground state molecules. We investigate their hyperfine structure and present a simple model to determine the singlet–triplet coupling of these states. Using Autler–Townes spectroscopy, we locate the rovibronic ground state of the ^23 Na ^39 K molecule ( $| {X}^{1}{{\rm{\Sigma }}}^{+},v=0,N=0\rangle $ ) and the second rotationally excited state N = 2 to unambiguously identify the ground state. We also extract the effective transition dipole moment from the excited to the ground state. Our investigations result in a fully characterized scheme for the creation of ultracold bosonic ^23 Na ^39 K ground state molecules.

Keywords

• STIRAP
• molecular spectroscopy
• ultracold polar molecules
• bosonic quantum gases