Ozone Ultraviolet Photolysis. I. The Effect of Molecular Oxygen

Abstract

To clarify the role of molecular oxygen in the photolytic decomposition of ozone, measurements of mixtures of ozone with helium, nitrogen, or oxygen were analyzed by the intermediate quantum yield method which separates effects due to fast and slow reactions by measuring the fast components shortly after flash photolysis. Analysis of the results gives the following rate constants (in liters/mole·second): O2 + O(1D) → O2(1Σg+) + O(3P), k4b = 1.5 ± 0.8 × 1011; O2(1Σg+) + O3 → 2O2 + O(3P), k3b = 4.0 ± 0.5 × 109. The efficiency of (4d) for forming O2(1Σg+) is found to lie in the range 1.0 ≥ α > 0.6. As a consequence of the high value of (k4b), which was previously neglected, rate constants reported previously should be revised as follows: O(1D) + O3 → 2O2, k2a = 4 ± 2 × 1010; O(1D) + N2 → O(3P) + N2, k4a = 2 ± 1 × 1010; O(1D) + Xe → O(3P) + Xe, k4c = 5 ± 2 × 1010. The quoted error limits are those which represent the fit of the data to the assumed mechanism with appropriate allowances for uncertainties due to minority processes.