To further probe changes to pre-heated silica NPs, Fig. shows typical sublimation behavior for a pre-heated silica NP in ~2.0 mTorr of Ar. The NP was trapped with the CO2 laser on, as described above, then heated only by the 532 nm thereafter. Q-stepping was done prior to the start of the kinetics measurements to measure Q (purple shaded region). The initial mass, Minitial, was 12.4 MDa, which is at the upper end of the mass distribution expected for the NP were extracted using linear fits to the data in each constant TNP period, and normalized to the surface areas estimated from the mass at the time of each Rsublimation period. Rsublimation values are given in the text boxes for the time periods labeled with Roman numerals. In some cases, the sublimation rate evolved significantly during a single constant TNP period, and in those cases, two linear regressions were fit to extract the initial and final Rsublimation values for that TNP. For example, Rsublimation during the first part of the 2300 K period (VIII) was ~5.56 x 10 -1 Da/sec/nm 2 , but slowed by ~50% by the end of that period (IX). Further evidence of NP evolution during sublimation is given by the observation that the Rsublimation values at each TNP tended to be higher as TNP was first ramped up, compared to the rates at the same TNP as the NP was cooled. Given that Tboil for silica (~3220 K) is lower than for bulk Si (3538 K), the slowing of the sublimation rate over time suggests that the NP continued to evolve toward more Si-rich composition during prolonged heating at high TNP. That, in turn, implies that CO2 laser pre-heating must leave the silica NPs with significant residual oxygen concentration that continues to be lost slowly at high TNP.