The photolysis of ozone by ultraviolet radiation III. The photolysis of dry ozone/oxygen mixtures at low pressures in a flow system

Abstract

The photolysis at λ = 254 nm of dry ozone + oxygen mixtures (90, 50 and 10% O 3 ) has been studied for partial pressures of ozone between 5 x 10 -2 and 2 Torr. A flow technique was employed, and the extent of ozone decomposition was followed absorptiometrically. Over the pressure range investigated, the quantum yield was virtually independent of ozone pressure for any ozone + oxygen mixture, and increasing dilution of the mixture from 90 to 10% ozone only slightly reduced the observed quantum yield. All quantum yields were near 4. The results are interpreted in terms of the formation of singlet molecular and atomic oxygen in the primary photochemical step; kinetic analysis of a hypothetical reaction scheme predicts quantum yields consistent with those observed.