Kinetic study of the absolute rate constant for the reaction of Rb + O 2 + N 2 over the range 709–897 K by time-resolved atomic resonance absorption spectroscopy

Abstract

We present a kinetic study of the reaction Rb + O 2 + N 2 → RbO 2 N 2 by time-resolved atomic resonance absorption spectroscopy. Rb(5 2S 1 2 ) was generated by the pulsed irradiation of RbI and RbCl vapors in equilibrium with their solids at elevated temperatures in the presence of O 2 and N 2. The atom was then monitored photoelectrically in the “single-shot mode” using the Rydberg transition at λ = 420.2 nm ( Rb(6p( 2P 3 2 )) ← Rb(5s( 2S 1 2 )) ) and atomic decay profiles were recorded and analyzed by computer. Absolute third-order rate constants ( k 3) were measured across the limited temperature range 709–897 K by two different kinetic procedures to yield an average experimental value for a single temperature of 800 K, namely, k 3(800 K) = 2.24 × 10 −30 cm 6 molecule −2 s −1. The temperature dependence of the rate constant was calculated using a Troe extrapolation based on unimolecular rate theory for the reverse process of dissociation to yield a form that can be fitted to the expression ln( k 3 cm 6 molecule −2 s −1) = −0.217 [ ln( T K )] 2 + 1.16 ln( T K ) −66.3 for the range 200–2000 K. This result is compared with analogous rate data for the reactions among Li, Na, K + O 2 + N 2.