Comment on "Measurement of a large Chemical Reaction Rate between Ultracold Closed-Shell ^{40}Ca Atoms and Open-Shell ^{174}Yb^{+} Ions Held in a Hybrid Atom-Ion Trap"

We estimate the radiative quenching rate of the ${}^{40}$Ca - ${}^{174}$Yb${}^{+}$ molecular ion and find that it under-estimates the value reported in recent experiments by about 5 orders of magnitude. We comment on possible explanations for this large discrepancy.