PHOTOLYSIS OF OZONE AND REACTIONS OF O(1(D)) ATOMS IN SOLID NITROGEN

The photochemistry of ozone in solid mixtures with nitrogen (mole frac tion, x, of ozone from 1 to 10(-4)) has been studied over the temperat ure range 9-25 K using 266 nm laser irradiation and infrared absorptio n spectroscopy. At high ozone concentrations (x greater than or equal to 0.1), the quantum yield for ozone decomposition is 2.0 +/- 0.3, bec ause each electronically excited O(D-1) atom formed in the primary pho tolysis step reacts with a second O-3 molecule. At low concentrations, the quantum yield is 0.7 +/- 0.2. No significant temperature dependen ce 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(D-1) atom. The atom may react with N-2 lattice molecules to form N2O or undergo quenching to O(P-3) followed by trap ping in an interstitial lattice site; the branching ratio is 1:4, resp ectively, at 10 K. This value leads to an estimate that O(D-1) encount ers an average of ten N-2 molecules prior to product formation.