Temperature-dependent kinetics study of the reactions of O(1D2) with N2 and O2

Abstract

A laser flash photolysis–resonance fluorescence technique has been employed to investigate the kinetics of the reactions of electronically excited oxygen atoms, O(¹D₂), with N₂ (k₁) and O₂ (k₂) as a function of temperature (197–427 K) in helium buffer gas at pressures of 11–40 Torr. The results are well-described by the following Arrhenius expressions (units are 10⁻¹¹ cm³ molecule⁻¹ s⁻¹): k₁(T) = (1.99 ± 0.06) exp{(145 ± 9)/T} and k₂(T) = (3.39 ± 0.03) exp{(63 ± 3)/T}. Uncertainties in the Arrhenius parameters are 2σ and represent precision only; estimated accuracies of reported k₁(T) and k₂(T) values at the 95% confidence level are ±10% around room temperature and ±15% at the temperature extremes of the study. The O(¹D₂) + O₂ kinetic data reported in this study are in very good agreement with available literature values. However, the kinetic data reported in this study (and two other new studies reported in this issue) suggest that the O(¹D₂) + N₂ reaction is significantly faster than previously thought, a finding that has important implications regarding production rates of tropospheric HO_x radicals as well as stratospheric HO_x and NO_x radicals calculated in atmospheric models.