Distribution and Relaxation of Vibrationally Excited Oxygen in Flash Photolysis of Ozone

Abstract

Absolute absorption by a sequence of bands in the Schumann—Runge series arising from oxygen molecules in vibrationally excited levels of the ground state formed by secondary processes of the flash photolysis of ozone was measured as a function of time. Measurements of bands arising from states v″ = 13 through v″ = 19 are analyzed in terms of a continuously generated initial distribution which relaxes to room temperature in single quantum steps. The vibrational relaxation rate constants are large and are interpreted as an efficient transfer of vibrational energy between ozone and excited oxygen. The relaxation process is consistent with a single quantum step model, and if deviations from this model are real, they are secondary. Vibrationally excited oxygen is formed initially in all of the observed states. The analysis does not give the shape of the initial distribution, but in magnitude it is consistent with a normal distribution of the energy of the reaction in all of the available modes of motion. The absolute concentration of excited oxygen in vibrational states 17 and higher is relatively too small for these molecules to have a major role in the chemistry of ozone photolysis.