UV absorption study of the dissociation of SO2 and SO in shock waves

The thermal decomposition of SO₂ and of the primary dissociation product SO have been studied in shock waves by the uv absorption technique. The controversy about SO₂ dissociation data from uv absorption signals was resolved and attributed to the extensive overlap of SO₂ and SO uv absorption spectra. The derived rate coefficients are k₁/Ar] = 10^15.6 exp(-420 kJmol^?1/RT) cm³mol^?1 s^?1 (temperature range 3000–5000 K) for SO₂ dissociation, and k₃/Ar] = 10^14.6 exp(-448 kJmol^?1/RT) cm³ mol^?1 s^?1 (temperature range 4000–6000 K) for SO dissociation. Anomalously high values of the apparent collision efficiencies β_c in SO₂ dissociation are attributed to marked contributions from excited electronic states.