Analysis of Data on the $B^{1}\Pi$ and $c^{3}\Sigma^{+}$ States of NaK

Current efforts to produce cold NaK molecules from cold atoms start with production of Feshbach resonances [1] followed by excitation to high-lying singlet or triplet states, and then one- or two-step possibly stimulated decay to $v$=0 of the $X$ ground state. Efficient use of these processes requires an accurate and detailed knowledge of NaK energy level structure. There have been numerous reports of excellent spectroscopic data on the NaK $B$ and $c$ states of Nak, as summarized in [2]. To meet requirements of current applications for a detailed, accurate compilation, we have constructed a model based on direct fits of experimental term values to potentials and spin-orbit coupling functions. Identification of regions of singlet-triplet $B-c$ state mixing is especially useful for current work. \\[4pt] [1] C.-H. Wu, M. Zwierlein, et al., PRL {\bf 109}, 085301 (2012). \\[0pt] [2] R. Ferber et al., JCP {\bf 112}, 5740 (2000).