Empirical LiK excited state potentials: connecting short range and near dissociation expansions.

We report on a high-resolution spectroscopic survey of 6 Li 40 K molecules near the 2S + 4P dissociation threshold and produce a fully empirical representation for the B 1 Π potential by connecting available short- and long-range data. The purpose is to identify a suitable intermediate state for a coherent Raman transfer to the absolute ground state, and the creation of a molecular gas with dipolar interactions. Starting from weakly bound ultracold Feshbach molecules, the transition frequencies to twenty-six vibrational states are determined. Our data are combined with long-range measurements [Ridinger et al. , EPL , 2011, 96 , 33001], and near-dissociation expansions for the spin-orbit coupled potentials are fitted to extract the van der Waals C 6 dispersion coefficients. A suitable vibrational level is identified by resolving its Zeeman structure and by comparing the experimentally attained g-factor to our theoretical prediction. Using mass-scaling of the short-range data for the B 1 Π [Pashov et al. , Chem. Phys. Lett. , 1998, 292 , 615620] and an updated value for its depth, we model the short- and the long-range data simultaneously and produce a Rydberg-Klein-Rees curve covering the entire range.