Decomposition of Ozone by O(1D)

Abstract

Photometric measurements of ozone decomposition following flash photolysis of O₃—inert‐gas mixtures are interpreted in terms of the time‐dependent quantum yield. Decomposition occurs in time segments which contribute increments to the quantum yield that depend on temperature, pressure, and sample composition. A major portion of the reaction $$\mathrm{O}{(}^1\mathrm{D)+}{\mathrm{O}}_3\text{→2}{\mathrm{O}}_2{\text{,\hspace{0.17em}\hspace{0.17em}k≥2.3×10}}^9\mathrm{liter}/\mathrm{mole}·\sec$$ is complete during the photolysis flash and has no temperature dependence in the range 205°—298°K. Processes which further enhance the quantum yield are much slower and depend on temperature, inert‐gas pressure, and composition in a way that has some correlation with the effectiveness of the gas in deactivating vibrationally excited O₂†. In N₂ a factor of 2 less O₃ is decomposed by the end of a flash than in He or Ar, indicating deactivation of the O(¹D) by N₂. The quantum yield is smaller in N₂ than in He or Ar but qualitatively similar in its pressure dependence. Some limitations in accounting for the results by an energy chain mechanism are discussed.