Reaction of NH(X3Σ–) with O2(3Σ –g) and O2(1Δg) in the gas phase

Abstract

The reactions NH(³Σ^–)+ O₂(³Σ^–_g)→ products (1), NH(³Σ^–)+ O₂(¹Δ_g)→ products (2) have been studied in an isothermal discharge-flow reactor with resonance absorption (H, O) and laser-induced fluorescence (OH, NH) detection methods. The NH radicals were produced via F + NH₃→ NH₂+ HF and NH₂+ F → NH + HF. The O₂(¹Δ_g) source was either a chemical generator [Cl₂+ H₂O₂→ O₂(¹Δ_g)+ 2HCl] or a microwave discharge in O₂. For reaction (1) a pressure-independent (1.2 ⩽p/mbar ⩽ 10.5) rate constant: k₁(T)= 7.6 × 10¹⁰ exp (–6.4 ± 0.6 kJ mol^–1/RT) cm³ mol^–1 s^–1 was determined in the temperature range 286 ⩽T/K ⩽ 543. For reaction (2) an upper limit for the rate constant: k₂(295 K)=(6 ± 1)× 10⁹ cm³ mol^–1 s^–1 was obtained at room temperature. The mechanisms of reaction (1) and (2) are discussed.