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Atomic resonance absorption spectroscopy has been used to investigate the thermal decomposition of N 2 O by monitoring the formation of O atoms behind reflected shock waves in the temperature range 1490-2490 K and at total pressures from 58 to 347 kPa, by using the mixtures of N 2 O highly diluted in Ar. For the chosen experimental conditions, the rate coefficient k 1,0 for the reaction N 2 O + Ar → N 2 + O + Ar had the greatest effect on the O atom concentration increase, so this reaction rate constant could be deduced by comparison between experiment and computed simulation. In the actual temperature range, we found k 1,0 (cm 3 mol −1 s −1 ) = 7.2 × 10 14 exp(−28878/T (K )), with an overall uncertainty evaluated to be less than 20%, by considering all the parameters, which contributed to uncertainties in the rate constant determination. The possible absorption at the O triplet emission line of N 2 O has been investigated. The absorption cross section of N 2 O at the O line has been estimated and taken into account for the determination of k 1,0 at high concentrations of N 2 O and at temperatures lower than 1850 K. The effect of the presence of impurities like H 2 O on rate constant determination has been examined and was found to be negligible. The choice of the rate coefficient for the consumption of O atoms by reaction with N 2 O and that of the high-pressure limiting rate coefficients k 1,∞ were also discussed. The rate constant reported in the present study was compared with the literature values and was found to be overall higher than those determined experimentally by other teams in the last decade. Finally, the effect of the modified constant value on reaction rate of diluted Ar-N 2 O mixtures and H 2 -N 2 O-Ar systems was investigated. In the temperature range 1500-2500 K, the use of the rate constant deduced from this study has led to a better prediction of N 2 O decomposition and N 2 O reduction by H 2 than with lower rate constants proposed in the literature.

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