Both Roxid and EEO2 are calculated assuming spherical NP shape, and therefore are upper limits on the true values. For small NPs, which are roughly spherical primary particles, these should be close to the true values, but for large NPs that are probably aggregates of smaller particles, the actual surface areas would be significantly higher than those of equivalent mass spheres, thus Roxid and EEO2 are likely to significantly overestimate the true kinetics. Just before time = 0 in Fig. , NP injection was stopped and the CO2 laser was turned on for a few seconds at 1% duty factor, irradiating any NPs in the trap with ~0.1 W average power, focused to a ~1 mm beam waist (intensity ≈ 10 W/cm 2 ). As shown in Fig. , this brief CO2 laser heating resulted in detection of significant emission by the APD. During each of the 30 second intervals indicated by solid vertical lines, resonance scans were used to measure Fz resonances (sharp dips indicated by blue or green dots) and emission spectra were measured to extract TNP. Fig. shows selected emission spectra measured during intervals with no CO2 laser excitation (red-shaded background in Fig. ).