The temperature dependence of the exchange reaction between oxygen atoms and dioxygen molecules studied by means of isotopes and spectroscopy

The temperature dependence of the rate constant for the exchange reaction between oxygen atoms and dioxygen molecules has been studied using the oxygen isotopes 16O and 18O. The reaction was studied by VIS-photolysis of ozone in the presence of isotopic dioxygen and with nitrogen as a bath gas at five different temperatures, 143 K, 173 K, 203 K, 253 K, and 295 K. High-resolution microwave spectroscopy was used to measure the composition of the ozone isotopomer mixtures and mass-spectrometry was used to determine the abundances of the isotopomeric dioxygen species formed during the reaction. The rate constant was determined to be kexchange=(2.66±0.78)×10−12 (T/300 K)−(0.88±0.26) cm3s−1 (±2σ ) or as the ratio between rate constants for exchange and for ozone formation, (4.67±1.3)×1021 (T/300 K)(1.74±0.19) cm−3 (±2σ).