State-of-the-art ab initio techniques have been applied to compute the potential energy curves of the (BaRb) + molecular ion in the Born-Oppenheimer approximation for the singlet and triplet states dissociating into the ground state 1 S Rb + ion and the Ba atom in the ground 1 S state, the lowest singlet or triplet D excited states, and for the singlet and triplet states dissociating into the ground state 2 S Rb atom and the ground state 2 S Ba + ion. The ground state potential energy was obtained with the coupled cluster method restricted to single, double, and nonperturbative triple excitations. The first triplet states in the Σ, Π, and ∆ symmetries were computed with the restricted open-shell coupled cluster method restricted to single, double, and nonperturbative triple excitations. All other excited state potential energy curves were computed using the equation of motion approach within the coupled-cluster singles, doubles, and linear triples framework.The long-range coefficients describing the electrostatic, induction, and dispersion interactions at large interatomic distances are also reported. The electric transition dipole moments governing the X 1 Σ → 1 Σ, 1 Π have been obtained as the first residue of the polarization propagator computed with the linear response coupled-cluster method restricted to single and double excitations. Nonadiabatic radial and angular coupling matrix elements, as well as the spin-orbit coupling matrix elements have been evaluated using the multireference configuration interaction method restricted to single and double excitations with a large active space. With these couplings, the spin-orbit coupled (relativistic) potential energy curves for the 0 + and 1 states relevant for the running experiments have been obtained. Finally, relativistic transition moments and nonadiabatic coupling matrix elements were obtained from the nonrelativistic results and spin-orbit eigenvectors. The electronic structure input has been employed in the single channel scattering calculations of the collisional cross sections between the Ba + ion and Rb atom. Both nonrelativistic and relativistic potentials were used in these calculations. Our results show that the inelastic cross section corresponding to the charge transfer from the Rb atom to the Ba + ion is much smaller than the elastic one over a wide range of energies up to 1 mK. This suggests that sympathetic cooling of the Ba + ion by collisions with ultracold Rb atoms should be possible.2

We investigate the problem of a single ion in a radio-frequency trap and immersed in an ultracold Bose gas either in a condensed or a non-condensed phase. We develop master equation formalism describing the sympathetic cooling and we determine the cooling rates of ions. We show that cold atomic reservoir modifies the stability diagram of the ion in the Paul trap creating the regions where the ion is either cooled or heated due to the energy quanta exchanged with the time-dependent potential.Comment: 11 pages, 4 figures, extended and substantially revised version of the articl

We consider a general problem of inelastic collision of particles interacting with power-law potentials. Using quantum defect theory we derive an analytical formula for the energy-dependent complex scattering length, valid for arbitrary collision energy, and use it to analyze the elastic and reactive collision rates. Our theory is applicable for both universal and non-universal collisions. The former corresponds to the unit reaction probability at short range, while in the latter case the reaction probability is smaller than one. In the high-energy limit we present a method that allows to incorporate quantum corrections to the classical reaction rate due to the shape resonances and the quantum tunneling.

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We investigate the static and dynamic properties of a Tonks-Girardeau gas in a harmonic trap with an eccentric δ-perturbation of variable strength. For this we first find the analytic eigensolution of the single particle problem and use this solution to calculate the spatial density and energy profiles of the many particle gas as a function of the strength and position of the perturbation. We find that the crystal nature of the Tonks state is reflected in both the lowest occupation number and momentum distribution of the gas. As a novel application of our model, we study the time evolution of the the spatial density after a sudden removal of the perturbation. The dynamics exhibits collapses and revivals of the original density distribution which occur in units of the trap frequency. This is reminiscent of the Talbot effect from classical optics.