The extent of ozone formation in the 1470hyphen;Aring; photolysis of oxygen and 1:1 heliummdash;oxygen mixture has been studied in a flow system as a function of pressure and temperature. A determination of the ozone quantum yield at atmospheric pressure gave phgr; = 2.0plusmn;0.2 in good agreement with previous values. At lower pressures, the production of ozone was found to decrease with pressure, and this effect has been interpreted as arising from the reaction of O(1D) with ozone. The quantitative evaluation of the ozone quantum yields in terms of O(1D) reactions provides ratios of rate constants for the reactions of O(1D) with ozone, oxygen, and helium. From the temperature dependence, the reaction with ozone is found to have an activation energy of 2.4plusmn;1.0 kcal/mole. Absolute rate constant estimates are obtained by the application of independent data.
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