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

B M Mclaughlin,H D L Lamb,I C Lane,J F Mccann

doi:10.1088/0953-4075/47/14/145201

Abstract

Ultracold hybrid ion–atom traps offer the possibility of microscopic manipulation of quantum coherences in the gas using the ion as a probe. However, inelastic processes, particularly charge transfer can be a significant process of ion loss and has been measured experimentally for the ion immersed in a Rb vapour. We use first-principles quantum chemistry codes to obtain the potential energy curves and dipole moments for the lowest-lying energy states of this complex. Calculations for the radiative decay processes cross sections and rate coefficients are presented for the total decay processes; and . Comparing the semi-classical Langevin approximation with the quantum approach, we find it provides a very good estimate of the background at higher energies. The results demonstrate that radiative decay mechanisms are important over the energy and temperature region considered. In fact, the Langevin process of ion–atom collisions dominates cold ion–atom collisions. For spin-dependent processes [] the anisotropic magnetic dipole–dipole interaction and the second-order spin–orbit coupling can play important roles, inducing coupling between the spin and the orbital motion. They measured the spin-relaxing collision rate to be approximately five orders of magnitude higher than the charge-exchange collision rate []. Regarding the measured radiative charge transfer collision rate, we find that our calculation is in very good agreement with experiment and with previous calculations. Nonetheless, we find no broad resonances features that might underly a strong isotope effect. In conclusion, we find, in agreement with previous theory that the isotope anomaly observed in experiment remains an open question.

Highlights

Charge transfer processes in ion−atom collisions are traditionally measured experimentally by their cross-sections and rate coefficient as a function of energy and temperature
Calculations for the radiative decay processes cross sections and rate coefficients are presented for the total decay processes; Yb+(6s 2S) + Rb(5s 2S) → Yb(6s2 1S) + Rb+(4p6 1S) + hν and Yb+(6s 2S) + Rb(5s 2S) → YbRb+(X1Σ+) + hν
The results demonstrate that radiative decay mechanisms are important over the energy and temperature region considered

Summary

Introduction

Charge transfer processes in ion−atom collisions are traditionally measured experimentally by their cross-sections and rate coefficient as a function of energy and temperature. Hybrid ion–atom systems are of great interest [12, 13] since these are inherently strongly-interacting systems with a longer-range potential, and inelastic processes can be studied These systems have been explored considering two-body collisions, in which both collision partners are translationally cold [14], and on the many-body level [15], where the sympathetic cooling of the ion with ultracold atoms was observed. The study of these systems in the quantum regime can be applied to hybrid ion–atom devices [16] and, in addressing fundamental many-body effects of ionic impurities such as mesoscopic molecule formation [17] and density fluctuations [18].

Electronic structure calculation

Theoretical method

Electronic states

Cross sections and collision rates

Conclusions