Experimental and theoretical studies of the N2+ + O2 reaction

Abstract

A technique by which ions are formed by resonance-enhanced multiphoton ionisation (REMPI) and detected by laser-induced fluorescence (LIF) has been employed to measure the kinetics of the N₂⁺ + O₂ reaction over the pressure range 5–484 Torr He at 296 K. Within this pressure range, measured rate constants for the reaction are found to increase by a factor of ∼2. It is well-established that the reaction proceeds predominantly by charge transfer at low pressure (<1 Torr). At higher pressures, the increase in rate constant for the reaction implies an increasing importance of the stabilisation of [N₂·O₂]⁺ complexes. However, the observed dependence of rate constants on pressure provides good evidence that charge transfer also proceeds via [N₂·O₂]⁺ complexes and that the contribution of charge transfer to the observed rate constant is pressure-dependendent. Extensive electronic structure calculations conducted at the QCISD/6-311G(d) level are presented and provide a framework to rationalise the experimental results.