Shock-Tube Measurement of the Rate of Dissociation of Nitrogen

The rate of dissociation of nitrogen behind strong shock waves in nitrogen—argon mixtures was determined using time-resolved interferometric measurements of gas density. Dissociation rates for impact by N2, N, and Ar were found by varying the mixture composition from 5% N2 to 100% N2. Temperatures from 6000° to 9000°K were covered in the experiments. The effectiveness of the N atom in causing N2 dissociation was found to be more than that of the N2 molecule by a factor of 10 to 15, whereas that of the argon atom was found to be less than that of N2 by a factor of 2.5. A large discrepancy between these results and those reported recently by Cary is partially resolved by an alternative interpretation of his data. A difficulty in fitting all of the data by using a single set of rate constants is described and several possible explanations are suggested.