Measurements of charge-exchange reaction rate constants between $\textrm{Ca}^+$ and Na in a hybrid atom-ion trap*

We present measurements of charge-exchage reaction rate constants between $\textrm{Ca}^+[^2\textrm{S}, {}^2\textrm{P}, {}^2\textrm{D}]$ and $\textrm{Na}[^2\textrm{S},{}^2\textrm{P}]$ using a hybrid trap. Our hybrid trap consists of a concentic magneto-optical trap MOT and linear Paul trap (LPT). The hybrid apparatus allows us to spatially overlap a trapped $\textrm{Ca}^+$ ion cloud or crystal with a cold Na MOT. $\textrm{Ca}^+$ ions that undergo charge-exchange or molecular photoassociation reactions with the Na atoms are lost from the LPT. An analysis of the trapped $\textrm{Ca}^+$ population's time-dependence yields the reaction rate constant between the trapped ions and co-trapped atoms. We can isolate the rate-constant for individual reaction pathways by independently controlling the internal electronic states of the Na atoms and/or the $\textrm{Ca}^+$ ions. Additionally, we explore the energy dependence of the rate constant by controlling the temperature of the laser-cooled $\textrm{Ca}^+$ ions. The reaction channel between $\textrm{Ca}^+[^2\textrm{S}]$ and $\textrm{Na}[^2\textrm{P}]$ is of particular interest, since an analysis of the Born-Oppenheimer potential energy curves reveal a barrier to the reaction for low temperature.