Ab initio Yb2 ground state potential revisited

Precision of the photoassociation spectroscopy of Yb dimer in degenerate gases is enough to improve the constraints on the new short-range gravity-like forces if the theoretical knowledge of interatomic potentials and non-Born-Oppenheimer interactions is refined [M. Borkowski et al. Sci. Rep. A 9, 14807 (2019)]. The ground-state interaction potential of ytterbium dimer is investigated at eXact 2-component core-correlated CCSD(T) level of ab initio theory in the complete basis set limit with extensive augmentation by diffuse functions. For the basis set of double-ζ quality, the comparison is made with the four-component relativistic finite-nuclei CCSD(T) calculations to identify the contraction of the dimer bond length as the main unrecoverable deficiency of the scalar-relativistic approximation. Empirical constraint on the number of bound vibrational energy levels of the Yb2 dimer is accounted for by employing the model semianalytical potential function containing the scale and shift parameters. The results support the previous evaluation of the Yb dimer potentials from the photoassociation spectroscopy data and provide an accurate and flexible reference for future refinement of the constraints on the short-range gravity-like forces by ultracold atomic spectroscopy. ∗ giorgio.visentin@skoltech.ru † a.buchachenko@skoltech.ru ‡ ptecmer@fizyka.umk.pl 1 ar X iv :2 10 7. 10 35 3v 2 [ ph ys ic s. at om -p h] 2 A ug 2 02 1