Another interesting question is how our N2O-NP etching kinetics compare to kinetics measured for various other forms of solid carbon. Fig. replots the etching efficiencies (Da/N2O collision) summarized in Fig. in Arrhenius format, i.e., ln(EEN2O) vs. 1000/T (solid lines/open circles), The slopes of our data give activation energies, Ea, of 160 kJ/mol for ramp 1 and 212 kJ/mol for ramp 2, but as discussed previously, Ea values extracted from experiments on single NPs are strongly affected by evolution of the NP surface under reaction conditions. This affects the Ea from ramp 1 most strongly, because that is when the fastest evolution occurred (Fig. ), and accounts for the artificially low value. Similar surface evolution also occurs in experiments with bulk powders or polycrystalline solids, but because different particles/crystal grains evolve differently, the effects tend to average out, allowing a steady-state to be reached. For a single NP under reaction conditions, a true steady-state is not possible, although the kinetics and Eas tend to converge toward stable values, indicating that the surface site distribution tends to reach a quasisteady state.