The photolysis of ozone by ultraviolet radiation. I. The photolysis of pure, dry ozone

Abstract

The photochemical decomposition of dry ozone has been studied at $\lambda$ = 2537 $\overset{\circ}{\mathrm A}$. The quantum yield for the photolysis of pure ozone was proportional to the pressure of ozone; the highest quantum yield recorded was 16.7 at a pressure of 5 cmHg ozone. Variation of light intensity did not markedly affect the quantum yield, and some evidence was found for a wall termination reaction. A reaction mechanism is proposed in which O($^1$D) atoms, formed in the primary photolysis, initiate a chain propagated by energy-rich oxygen molecules. A discussion of the nature of the energy-rich molecules is presented. Addition of inert gases to the pure ozone reduces the quantum yield to a limiting value of two. This is explained in terms of the deactivation of the energy-rich oxygen molecule. In the presence of oxygen, the quantum yield tends to zero, as a result of the reverse reaction $O + O_2 + M \rightarrow O_3 + M.$