Kinetic study of the absolute rate constant for the reaction between K + N 2O by time-resolved atomic resonance absorption spectroscopy

Abstract

We present a kinetic study of the reaction K+N 2O→KO+N 2 (k R) across the temperature range 701–903K by direct monitoring of atomic potassium in the time-resolved mode. K(4 2S 1 2 ) was generated by the pulsed irradiation of KI vapor at elevated temperatures and studied by time-resolved atomic resonance absorption spectroscopy in the “single-shot mode” using the Rydberg doublet at λ = 404 nm ( K(5 2P J) ← K(4 2S 1 2 ) ). Measurements of the rate constant, k R, at different temperatures yielded the following Arrhenius form: k r=(1.4±0.10)×10 −10exp −8.6±1.2kJ mol −1 RT cm 3 molecule −1S −1 , a result similar to that for the analogous reaction between Na + N 2O, and permitting reaction (1) to be employed as a titration technique for the quantitative preparation of KO and the subsequent kinetic study of this diatomic species. Reaction (1) also provides a kinetic standard for atomic potassium at elevated temperatures.