Towards sympathetic rotational cooling of CaH$^+$ in a hybrid atom-ion trap

A hybrid ion and magneto-optical trap is proposed to be a good environment for achieving the sympathetic cooling of molecular ions. We have previously shown that simultaneous trapping and spatial overlap of laser cooled Ca$^+$ with CaH$^+$ allows for sympathetic cooling of CaH$^+$. Coulomb interactions with calcium ions cool the translational motion of the molecular ion, and we expect the addition of interactions with potassium cool the internal states. We have observed charge exchange interactions between the coolants (Ca$^+$ and K) which can be minimized through state manipulation of the calcium ions. We present results of charge exchange reactions between trapped Ca$^+$ and K and our plans for the sympathetic rotational cooling of CaH$^+$.