Measurement of the Rate of Dissociation of Oxygen

The rate of dissociation of oxygen behind strong shock waves in pure oxygen, in mixtures of oxygen and argon, and in air was determined over a temperature range from 2800°K to 5000°K. A long duration spark interferometer and drum camera were used to measure the shock speed and the variation of density behind the shock. The dissociation rate determined from the data can be represented by a collision theory equation, assuming that all of the available energy of vibration of the particles is transferred to dissociation in an inelastic collision. Oxygen atoms were found to be very effective in causing dissociation of oxygen molecules; the measured transition probability for energetically possible collisions between an oxygen atom and an oxygen molecule was 1.7, that for collisions between two oxygen molecules was 0.24. Collisions between nitrogen and oxygen molecules in air were found to be relatively ineffective in causing dissociation of oxygen; the measured rate of dissociation of oxygen in air was less than a factor of 2 larger than that caused by collisions between oxygen atoms and molecules alone.