LiK B¹Π potential: combining short and long range data

We present spectroscopic measurements of the long range states of the ⁶Li⁴⁰K molecule near its Li(4²S_1/2) + K(4²P_3/2) asymptote which in combination with existing data in the short range lead to the full characterization of the B¹Π potential with high spectroscopic resolution. Starting from weakly bound ultracold Feshbach molecules, we performed one-photon loss spectroscopy of the high-lying levels of the B¹Π potential. A total of twenty-five vibrational lines were observed close to the asymptote which were combined with existing data from photo association spectroscopy [1]. Extrapolation of the latter led to the assignment of our observed lines to vibrational levels in the spin-orbit coupled potentials near the dissociation threshold. For our Hund’s case (c) molecules, a complete set of data is presented for the Ω=1^up state, by combining the long range measurements with data from the short range states of the B¹Π from heat-pipe spectroscopy of the ⁷Li³⁹K molecule [2]. Using mass scaling, we modelled the short range and the long range part of the potential simultaneously and produced the Rydberg-Klein-Rees (RKR) curve for the complete potential. The vibrational energies and the rotational constants were defined in terms of Dunham representation and compared with a mixed near-dissociation / Dunham expansion. We present the improved empirical curve for the long range part of the Ω=1^up state. [1] A. Ridinger, et. al., EPL, 96, 33001, (2011); [2] A. Pashov, et. al., Chem. Phys. Lett. 292, 615-620 (1998)