Laser induced fluorescence studies of iodine oxide chemistry Part II. The reactions of IO with CH3O2, CF3O2 and O3

Abstract

The technique of pulsed laser photolysis was coupled to laser induced fluorescence detection of iodine oxide (IO) to measure rate coefficients, k for the reactions IO + CH₃O₂ → products (R1, 30–318 Torr N₂), IO + CF₃O₂ → products (R2, 70–80 Torr N₂), and IO + O₃ → OIO + O₂ (R3a). Values of k₁ = (2 ± 1) × 10⁻¹² cm³ molecule⁻¹ s⁻¹, k₂ = (3.6 ± 0.8) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹, and k_3a <5 × 10⁻¹⁶ cm³ molecule⁻¹ s⁻¹ were obtained at T = 298 K. In the course of this work, the product yield of IO from the reaction of CH₃O₂ with I was determined to be close to zero, whereas CH₃OOI was formed efficiently at 70 Torr N₂. Similarly, no evidence was found for IO formation in the CF₃O₂ + I reaction. An estimate of the rate coefficients k(CH₃O₂ + I) = 2 × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹ and k(CH₃OOI + I) = 1.5 × 10⁻¹⁰ cm³ molecule⁻¹ s⁻¹ was also obtained. The results on k₁–k₃ are compared to the limited number of previous investigations and the implications for the chemistry of the marine boundary layer are briefly discussed.