Structure and interactions of ultracold Yb ions and Rb atoms

Abstract

In order to study ultracold charge-transfer processes in hybrid atom-ion traps, we have mapped out the potential-energy curves and molecular parameters for several low-lying states of the Rb, Yb+ system. We employ both a multireference configuration interaction and a full configuration interaction (FCI) approach. Turning points, crossing points, potential minima, and spectroscopic molecular constants are obtained for the lowest five molecular states. Long-range parameters, including the dispersion coefficients, are estimated from our ab initio data. The separated-atom ionization potentials and atomic polarizability of the ytterbium atom (alpha(d) = 128.4 atomic units) are in good agreement with experiment and previous calculations. We present some dynamical calculations for (adiabatic) scattering lengths for the two lowest (Yb, Rb+) channels that were carried out in our work. However, we find that the pseudopotential approximation is rather limited in validity and only applies to nK temperatures. The adiabatic scattering lengths for both the triplet and singlet channels indicate that both are large and negative in the FCI approximation

Ultracold, radiative charge transfer in hybrid Yb ion–Rb atom traps

“…The dissociation energy of Sayfutyarova et al [32] is 3496 cm −1 (0.4334 eV), almost twice the value of Lamb and co-workers [22], who obtained a value of 0.2202 eV. We note also that the equilibrium distance R e also occurs at a shorter bond length of 8.088a 0 [32], compared to our finding which gave R e = 9.031a 0 [22]. Fig.…”

“…Low lying potential energy curves (PEC's) as a function of internuclear distance out to R = 50a.u. are computed and in the present investigation we extend our earlier work [22] to calculate the transition dipole moments between the 1,3 Σ + states. As in our previous work we use an active two-electron model within a multi-reference configuration interaction (MRCI) and a full-configuration interaction (FCI) framework to calculate all the potentials.…”

“…Thus the experimental study of the quantum coherence of charge transfer [15] was based on schematics of the energy curves. This prompted our in depth investigations [22] to map the lowest adiabatic states and the static properties of the molecular ion, in particular the turning points, potential minima, and crossing points of the lowest molecular energies. In addition to this, the dissociation energies and molecular constants provide useful spectroscopic data for dynamical investigations [32].…”

Formation of molecular ions by radiative association of cold trapped atoms and ions

“…This discrepancy of 113 cm −1 also holds for the spacing between the Yb + ( s 6 )+(Alk)(ns) and the Yb( s S 6 2 1 )+(Alk) + asymptotes (equal to 16864.8 cm −1 in our method, in good agreement with the experimental value of 16752.2 cm −1 [64]). It favorably compares to the discrepancy of 322 cm −1 reported in [66], and to [67] which reported an energy difference of 16279 cm −1 between these two asymptotes. Finally, in their work on LiYb + [13] the authors report an ionization energy for the Yb ground state of 50267 cm −1 .…”

“…As already quoted above, the cases of RbYb + and LiYb + are peculiar, as the Yb + ion and Yb atom have not been treated with a large ECP before. Tables 1 and 2 reveal a contrasted situation for RbYb + in comparison with the results of [66,67,74] that are all obtained with similar approaches based on small core ECPs. Our values for R e and D e of the X PEC are in good agreement with those of [67], while the potential well depth from [66,74] is twice smaller than ours, with a minimum located at a significantly larger distance.…”