Measurement of a Large Chemical Reaction Rate between Ultracold Closed-Shell 40Ca Atoms and Open-Shell 174Yb+ Ions Held in a Hybrid Atom-Ion Trap

Ultracold Yb-174(+) ions and Ca-40 atoms are confined in a hybrid trap. The charge exchange chemical reaction rate constant between these two species is measured and found to be 4 orders of magnitude larger than recent measurements in other heteronuclear systems. The structure of the CaYb+ molecule is determined and used in a calculation that explains the fast chemical reaction as a consequence of strong radiative charge transfer. A possible explanation is offered for the apparent contradiction between typical theoretical predictions and measurements of the radiative association process in this and other recent experiments.