Beyond-Born-Oppenheimer effects in sub-kHz-precision photoassociation spectroscopy of ytterbium atoms

Abstract

We present high-resolution two-color photoassociation spectroscopy of Bose-Einstein condensates of ytterbium atoms. The use of narrow Raman resonances and careful examination of systematic shifts enabled us to measure 13 bound state energies for three isotopologues of the ground state ytterbium molecule with standard uncertainties on the order of 500 Hz. The atomic interactions are modeled using an ab initio based mass scaled Born-Oppenheimer potential whose long range van der Waals parameters and total WKB phase are fitted to experimental data. We find that the quality of the fit of this model, of about 112.9 kHz (RMS) can be significantly improved by adding the recently calculated beyond-Born-Oppenheimer (BBO) adiabatic corrections [

Absolute numbering of asymptotic vibrational levels of diatomic molecules from cold-physics experiments

“…The difference between our analysis and that of Ref. [2] is that the first one is much simpler, whereas the second one provides a potential energy curve with correct near asymptotic behaviour and the vibrational numbering comes as a consequence.…”

“…We shall discuss the case of Yb 2 molecule in more details than the other ones to make our presentation more instructive. In Table I we Therefore we just changed the sign of the relative vibrational quantum numbers from [2]. We shall use label n hereafter for the proper relative vibrational quantum numbers.…”

“…However, this is not the case for the other isotopologues, because the numbering used in Ref. [2] was introduced independently for each of them. The same potential curve may support a different number of levels for isotopologues of different masses, for instance the least bound levels with p = 1 in 170 Yb 2 and p = 1 in 174 Yb 2 do not necessarily correspond to the same absolute quantum number v (and to the same relative number n).…”

“…In a series of recently published papers, measurements of binding energies for the few last rovibrational levels in the ground electronic state were reported in RbYb [1], Yb 2 [2], CsYb [3] and RbSr [4] molecules. These studies were focused on the scattering properties of the corresponding ultra-cold atomic species, including the interatomic interaction potentials and scattering lengths.…”

Quantum chaos in Feshbach resonances of the ErYb system

“…The dissociation energy for ErYb obtained with broken-symmetry CCSD(T) is 639cm -1 . This value can be compared with experimental estimates of the dissociation energy for Yb 2 of 738cm −1 [55] and RbYb of 785cm −1 [56]. In the latter case, ab initio calculations based on the ECP60MDF core potential as reported in [56] predicted a well depth of 704 cm −1 , hence we expect our result could be underestimated by at most 10% and conclude that the ECP60MDF core potential as used for the Yb atom is sufficient to satisfactorily describe the ErYb interaction.…”