Predissociation of the Oxygen Molecule

Abstract

In the emission spectrum of the oxygen molecule no bands in the Runge system, ³Σ_u^—→³Σ_g^—, having ν′>2 have ever been observed. The absence of these emission bands as well as evidence of broadened rotation lines in the ν′>2 absorption bands suggests that in the ³Σ_u^— state vibration levels above the second undergo predissociation. Rassetti's observations of the fluorescence spectrum of oxygen as well as recent photochemical results support this conclusion. Although it cannot be said that any one of these lines of evidence provides rigorous proof that the oxygen molecule predissociates, collectively they present a convincing argument for the occurrence of predissociation. Radiationless transition from the ³Σ_u^— state is doubtless to the ³II_u state formed from normal atoms. On the basis of the present interpretation the initial process in the photochemical reactions of oxygen caused by light in the region of Schumann‐Runge band absorption is the formation of normal ³P atoms as a result of the predissociation, rather than the reaction of an optically excited molecule with a normal molecule as heretofore has been supposed.