This simply reflects the short measurement times used for each PN2O step, giving uncertainty in the raw slopes of ~30 to 40 Da/sec. For the higher PN2O values ("e" -"h"), there were obvious increases in the rate of mass loss when N2O was added, such that the baseline-subtracted etching rate was -1055 ± 85 Da/sec at "h". The corresponding EEN2O values are shown in the second text inset, with values given only for the higher pressures ("e"-"h"), where the baseline-subtracted rates had reasonable uncertainties. Over this N2O pressure range, EEN2O increased slightly from 4.0 x 10 -5 Da/collision at "e" to 5.0 x 10 -5 Da/collision at "h". This increase in EEN2O could be taken as evidence of a pressure effect on reactivity, however, it is important to bear in mind that At 1900 K, sublimation is fast, thus Rbaseline ≈ Rsublimation. In the first experiment (Fig. ), the NP was held at 1900 K for ~1.5 hours, trapped in Ar and in Ar with varying pressures of N2O.