Excited ozone is a possible source of atmospheric N2O

Abstract

In the formation of ozone from O and O2 in the ground state, the products of the reaction may include electronically excited forms of ozone (O*3) which are spectroscopically recognizable in pulsed radiolysis and flash photolysis experiments1–4. Indeed, it has been suggested that in the three-body recombination reaction O+O2+M→O*3+M(1) there is a 62% chance that the ozone product will be in an excited form. Although the identity of these excited precursors of ozone is not known, excited 3B2, 3A2 and 1A2 states of bent ozone and the cyclic ozone have been suggested5–7, and the existence of electronically excited states of bent ozone below its dissociation limit has been corroborated by large-angle electron scattering experiments8. Thus, more than one form of internally excited ozone precursor may be involved. It has been estimated9 that ∑n(O*3) ≈ (100–1,000) · n (O1D) in the stratosphere. Consequently, even with moderate reactivity, O*3 may be chemically significant in the stratosphere. We now hypothesize that some of the internally excited ozone, probably that which is electronically excited, may be a potential source of N2O through the gas-phase reacton (2a), O*3 + N2→N2O + O2 (2a) →O3 + N2 (2b)