Atmospheric chemistry of iodine anions: elementary reactions of I−, IO−, and IO2− with ozone studied in the gas-phase at 300 K using an ion trap

Abstract

Using a radio-frequency ion trap to study ion–molecule reactions under isolated conditions, we report a direct experimental determination of reaction rate constants for the sequential oxidation of iodine anions by ozone at room temperature (300 K). The results are R1: I⁻ + O₃ → IO⁻ + O₂, k₁ = (7 ± 2) × 10⁻¹² cm³ s⁻¹; R2: IO⁻ + O₃ → IO₂⁻ + O₂, k₂ = (10 ± 2) × 10⁻⁹ cm³ s⁻¹; R3: IO₂⁻ + O₃ → IO₃⁻ + O₂, k₃ = (16 ± 2) × 10⁻⁹ cm³ s⁻¹. More oxidized forms such as IO₄⁻ and IO₅⁻ were not observed. Additionally, we performed quantum chemical calculations to elucidate the energetics of these oxidation reactions.