Abstract: | Measurements of the NO-catalyzed dissociation of I2 in Ar in incident shock waves were carried out in the temperature range of 700°-1520°K and at total concentrations of 5 × 10?6-6 × 10?5 mol/cm3, using ultraviolet-visible absorption techniques to monitor the disappearance of I2. It was shown that the main reaction responsible for the disappearance under these conditions is I2 + NO → INO + I, for which a rate coefficient of (2.9 ± 0.5) × 1013 exp-(18.0 ± 0.6 kcal/mol)/RT] cm2/mol·sec was determined. The INO formed dissociates rapidly in a subsequent reaction. The reaction, therefore, constitutes a “chemical model” for a “thermal collisional release mechanism.” Preliminary measurements of the rate coefficient for I2 + NO2 → INO2 + I are also presented. Combined with information on the reverse reactions obtained in earlier room temperature experiments, these results lead to accurate values of ΔH°f for INO and INO2 equal to 29.7 ± 0.5 and 15.9 ± 1 kcal/mol, respectively. |