Molecular dynamics of the reaction O(21 D)+ N2O ? NO + NO

Abstract

Photodissociation of N₂O at wavelengths ∼200 nm, produces O(2¹D) atoms, which react with undecomposed N₂O. The vibrational energy distribution among the products of the reaction O(2¹D)+ N₂O → NO + NO, ΔH=–334 kJ mol^–1(4) has been measured, by investigation of the flash photolysis of normal and isotopically labelled N₂O (¹⁵NNO). The total energy is divided equally between the two products, with the major part appearing in translation. The vibrational energy yield is ∼20%(corrected for vibrational relaxation). Although the O(2¹D) atoms carry translational, as well as electronic excitation, their moderation by added Ar does not alter the observed vibrational energy distribution. The yields of NO are reduced by gases which deactivate or react with O(2¹D) and NO provides a convenient spectroscopic marker for measuring relative rate constants of removal of O(2¹D) atoms. Possible reaction pathways are considered in the light of these and other experimental observations, and the results of approximate SCF molecular orbital calculations for the ONNO dimer. It is suggested that reaction (4) occurs through the intermediacy of an ONNO complex.