Kinetic Study by EPR of the Production and Decay of SO(1Δ) in the Reaction of O2(1Δg) with SO(3Σ−)

Abstract

The existence of the reaction of O₂(¹Δ_g) with ground‐state SO(³Σ⁻) to produce SO(¹Δ) and ground‐state ${\mathrm{O}}_2{(}^3{\Sigma }_g^{-})$ has been confirmed using a fast‐flow system and electron paramagnetic resonance detection of all four species. A kinetic study of this reaction has resulted in the determination of the absolute value of the rate constant: ${\text{(2.12 ± 0.22 × 10}}^8)\mathrm{liter\; mole}\text{−1·}\sec \text{.−1}$ The reaction is therefore faster, by an order of magnitude, than any quenching process by a neutral species yet reported for O₂(¹Δ_g) in the gas phase, reaction or deactivation. The rapid rate is in rough accord with predictions derived from observations of similar atomic processes by other workers, indicating that the reactive process probably involves simple spin‐allowed transfer of electronic energy in which a resonance situation is approximated. The mechanism for the decay of the SO(¹Δ) produced in the reaction has also been determined. It is shown that SO(¹Δ) is heterogeneously deactivated to SO(³Σ⁻) at the reaction vessel walls with an efficiency about four orders of magnitude greater than that observed for deactivation of O₂(¹Δ_g) to O₂(³Σ_g⁻). Such a high wall deactivation efficiency may explain the spectroscopic observations by other workers of SO(³Σ⁻) but not the expected SO(¹Δ) in the pyrolysis products of ethylene episulfoxide.