| Abstract
| - The ozone decomposition quantum yield (Φ) in millimolarand higher-concentration aqueous tertiary butanol solutionis 0.64 ± 0.05 (observed over a wavelength range from250 to 280 nm) and rises toward lower tertiary butanolconcentrations (Φ ≈ 1.5 at 10-5 M at pH 2) on accountof the onset of the well-known •OH-radical-induced chainreaction. The destruction of the organic is initiated byhydrogen-atom abstraction through OH radicals which areproduced via the reaction of the photolytically generatedO(1D) with the solvent water at a quantum yield of Φ(•ΟΗ)of about 0.1. There is no decomposition of ozone in thedark on the time scale of the photolysis experiment. Theefficiency of tertiary butanol destruction with respect to ozoneconsumption ([O3]o = 3 × 10-4 M), defined by the ratio Δ[t-BuOH]/Δ[O3], termed η(t-BuOH), is 0.26 at millimolartertiary butanol concentrations, determined at the stageof essentially complete ozone consumption. It diminishestoward lower tertiary butanol concentrations(Δ[t-BuOH]/Δ[O3] ≈ 0.17 at [t-BuOH]o = 1 × 10-4 M). Partof the effect of the ozone, apart from being a source of •OH radicals, rests on the intervention of HO2•/O2•- which isproduced in the course of the peroxyl-radical chemistryof the tertiary butanol in this dioxygen-saturated environmentand converted into further •OH radical by reaction withozone. Moreover in this system, organic free radicals andperoxyl radicals react with the ozone. On the basis ofthe experimental and mechanistic-simulation data, thequantum yield of direct (by hv) ozone cleavage in aqueoussolution is estimated at about 0.5.
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