Dissociative Recombination of FeO(+) with Electrons: Implications for Plasma Layers in the Ionosphere.

The dissociative recombination (DR) of FeO+ ions with electrons has been studied in a flowing afterglow reactor. FeO+ was generated by the pulsed laser ablation of a solid Fe target, and then entrained in an Ar+ ion/electron plasma where the absolute electron density was measured using a Langmuir probe. A kinetic model describing gas-phase chemistry and diffusion to the reactor walls was fitted to the experimental data, yielding a DR rate coefficient at 298 K of k(FeO+ + e–) = (5.5 ± 1.0) × 10–7 cm3 molecule–1 s–1, where the quoted uncertainty is at the 2σ level. Fe+ ions in the lower thermosphere are oxidized by O3 to FeO+, and this DR reaction is shown to provide a more important route for neutralizing Fe+ below 110 km than the radiative/dielectronic recombination of Fe+ with electrons. The experimental system was first validated by measuring two other DR reaction rate coefficients: k(O2+ + e–) = (2.0 ± 0.4) × 10–7 and k(N2O+ + e–) = (3.3 ± 0.8) × 10–7 cm3 molecule–1 s–1, which are in good agreement wit...