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 experiments^1–4. 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 suggested^5–7, 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)