The role of oxygen dimer in oxygen photolysis in the Herzberg continuum: a temperature dependence study

The effect of temperature on ozone formation in the 214-nm photolysis of oxygen was investigated as a means of assessing the role of oxygen dimer in the photodissociation of oxygen excited in the Herzberg continuum. Throughout the entire temperature range of 297-387 K, evidence was found for the importance of (O{sub 2}){sub 2} in oxygen photolysis. For the reaction 2O{sub 2}{leftrightarrow} (O{sub 2}){sub 2} a {Delta}H value of -0.2 {plus minus} 0.5 kcal mol{sup {minus}1} is estimated. This result indicates that (O{sub 2}){sub 2} is a very weakly bound metastable dimer, the formation of which nevertheless has a pronounced effect on oxygen absorption cross sections in the Herzberg continuum.