Photolysis of ozone and reactions of O(1D) atoms in solid nitrogen Original Research Article

The photochemistry of ozone in solid mixtures with nitrogen (mole fraction, x, of ozone from 1 to 10−4) has been studied over the temperature range 9–25 K using 266 nm laser irradiation and infrared absorption spectroscopy. At high ozone concentrations (x ⩾ 0.1), the quantum yield for ozone decomposition is 2.0 ± 0.3, because each electronically excited O(1D) atom formed in the primary photolysis step reacts with a second O3 molecule. At low concentrations, the quantum yield is 0.7 ± 0.2. No significant temperature dependence of the yield is observed. The results suggest that the equilibrium geometry of an ozone molecule isolated in nitrogen favors direct cage escape of the nascent O(1D) atom. The atom may react with N2 lattice molecules to form N2O or undergo quenching to O (3P) followed by trapping in an interstitial lattice site; the branching ratio is 1:4, respectively, at 10 K. This value leads to an estimate that O(1D) encounters an average of ten N2 molecules prior to product formation.