A brief (~2 minute) period of significant etching occurred when N2O was first introduced, but the mass quickly stabilized after ~52 kDa had been etched (~2% of a monolayer). This brief burst of fast etching is attributed to the presence of surface defects created by sublimation (at "d") after the end of the preceding 1800 K N2O etching period, i.e., to the same effect that briefly caused fast etching when O2 was first introduced after the 1900 K period. After this initial etching, no further mass loss occurred either in N2O or during the subsequent O2 exposure period, i.e., the NP was passivated toward both N2O and O2.