UV absorption study of the dissociation of SO 2 and SO in shock waves

The thermal decomposition of SO 2 and of the primary dissociation product SO have been studied in shock waves by the uv absorption technique. The controversy about SO 2 dissociation data from uv absorption signals was resolved and attributed to the extensive overlap of SO 2 and SO uv absorption spectra. The derived rate coefficients are k 1 /[Ar] = 10 15.6 exp(‐420 kJmol −1 / RT ) cm 3 mol −1 s −1 (temperature range 3000–5000 K) for SO 2 dissociation, and k 3 /[Ar] = 10 14.6 exp(‐448 kJmol −1 / RT ) cm 3 mol −1 s −1 (temperature range 4000–6000 K) for SO dissociation. Anomalously high values of the apparent collision efficiencies β c in SO 2 dissociation are attributed to marked contributions from excited electronic states.