Kinetics of the Reaction of Iodine Atoms with HO2 Radicals

Article abstract of DOI:10.1021/j100370a036

The rate coefficient (k₇) for the reaction of iodine atoms with HO2 radicals, I + HO2 -> HI + O2, has been measured directly with use of the discharge-flow/EPR technique, and the molecular-modulation/UV-absorption spectroscopy technique.Discharge-flow measurements were made under pseudo-first-order conditions with iodine atoms in large excess over HO2.Molecular-modulation measurements were made with iodine atoms in excess over HO2, but the I + HO2 raection was occuring in competition with the self-reaction of HO2.The value of k7 determined at 298 K by these complementary methods agree within the combined experimental errors and provide a value of (3.8+/-1.0)x10^-13 cm³ molecule^-1 s^-1.Further measurements made over the temperature range 283-353 K with the molecular-modulation technique allow recommendation of the following expression: k₇=(1.47+/-0.63) x 10^-11 exp(-(1090+/-130)/T).The potential significance of this reaction as a sink for iodine in the troposphere and the other aspects of tropospheric iodine chemistry are considered with a simple model of the atmospheric boundary layer.