Stable isotope fractionation during ultraviolet photolysis of N₂O

The biogeochemical cycling of nitrous oxide plays an important role in greenhouse forcing and ozone regulation. Laboratory studies of N₂O:N₂ mixtures irradiated between 193–207 nm reveal a significant enrichment of the residual heavy nitrous oxide isotopomers. The isotopic signatures resulting from photolysis are well modeled by an irreversible Rayleigh distillation process, with large enrichment factors of ε_15,18(193 nm) = −18.4,-14.5 per mil and ε_15,18(207 nm) = −48.7,-46.0 per mil. These results, when combined with diffusive mixing processes, have the potential to explain the stratospheric enrichments previously observed.