Evidence for O-atom exchange in the O(1D) + N2O reaction as the source of mass-independent isotopic fractionation in atmospheric N2O

Abstract

Recent experiments have shown that in the oxygen isotopic exchange reaction for O(1D) + CO2 the elastic channel is approximately 50% that of the inelastic channel [Perri et al., 2003]. We propose an analogous oxygen atom exchange reaction for the isoelectronic O(1D) + N20 system to explain the mass-independent isotopic fractionation (MIF) in atmospheric N20. We apply quantum chemical methods to compute the energetics of the potential energy surfaces on which the O(1D) ± N2O reaction occurs. Preliminary modeling results indicate that oxygen isotopic exchange via O(1D) ± N2O can account for the MIF oxygen anomaly if the oxygen atom isotopic exchange rate is 30 50% that of the total rate for the reactive channels. Copyright 2004 by the American Geophysical Union.