The relative uncertainty in repeated Q/M determinations is due mostly to scatter in the F z resonance fits due to the limited signal/noise in the raw F drive sweeps (Fig. inset) and therefore is anticorrelated with the emission brightness of the NPs, which increases with NP size and T NP , but also varies with the emissivity of the NP material. For typical NPs above ~1300 K, the scatter in repeated F z measurements is less than ~0.2 %. Longer resonance sweep times can be used to reduce the scatter in Q/M into the few parts-per-million range, but for kinetics work, the uncertainty resulting from 0.2 % scatter in F z is insignificant.