  We present measurements of the charge-exchange reaction rate between neutral
sodium (Na) and ionized calcium (\ce{Ca+}) in a hybrid atom-ion trap, which is
comprised of a Na magneto-optical trap concentric with a linear Paul trap. Once
the Na and \ce{Ca+} are co-trapped, the reaction rate is measured by
continuously quenching the reaction product \ce{Na+} from the ion trap, and
then destructively measuring the decay of the remaining ion population. The
reactants' electronic state and temperature are experimentally controlled,
allowing us to determine the four individual reaction-rates between
$\text{Na}[\text{S~or~P}]$ and $\text{Ca}^+[\text{S~or~D}]$ at different
collision energies. With the exception of the largest reaction-rate channel
($\text{Na}[\text{S}]+\text{Ca}^+[\text{D}]$), our rates agree with classical
Langevin rate limit. We have also found evidence of reactant collision-energy
thresholds associated with two of the four entrance-channels.
