ИСТИНА

There have been many spectroscopic and theoretical studies of the LiRb molecule investigating its electronic structure both using experimental as well as theoretical methods. Among these is a spectroscopic study [1] investigating the depletion spectra of the A1Σ+-b3Π complex of ultracold molecules, observing 41 vibrational levels (see Fig 1, left) with rotational quantum number J=1. Here we have used the coupled-channel deperturbation model to describe the singlet-triplet mixing of each level. We used a 2×2 model Hamiltonian, accounting for the spin-orbit (SO) interaction within the complex. Two different methods were used to represent fitting potentials of the mixed states and SO coupling function. In method 1 both interatomic potentials were approximated using the expanded Morse oscillator function, the coefficients of which were then fitted, in method 2 the initial trial point-wise potentials were constructed and fitted using cubic splines. In both methods, the fit was additionally constrained by minimizing not only the differences between the experimental and theoretical term values, but also the differences between the fitted potentials and SO coupling and their ab initio counterparts [2]. As a result, the most experimental terms were fitted with an accuracy of about 0.02 cm-1, which is comparable with experimental accuracy, or better. And only two levels were fit with an accuracy of worse that 0.05 cm-1. Among them is the vibrational level v=9 of the b3Π state, which lies energetically right at the point where the b3Π state intersects with the repulsive branch of a3Σ+ state. Additionally, we were able to determine the mixing coefficients for all experimental levels, with the vA=3,6 and vb=10,12 of the A1Σ+ and b3Π states respectively, exhibiting the greatest degree of mixing. References: 1. I. Stevenson, D. Blasing, A. Altaf, Y. P. Chen, D. S. Elliott, H. Ishikawa, N. Nakamura, M. Yoshida, M. Takigawa, P. Babkevich, N. Qureshi, H. M. Rønnow, T. Yajima and Z. Hiroi, Phys. Rev. A 95, 062503 (2016). 2. E. A. Bormotova, S. V. Kozlov, E. A. Pazyuk, A. V. Stolyarov, W. Skomorowski, I. Majewska and R. Moszynski, Phys. Rev. A 99, 012507 (2019).