Absorption Cross Section and Kinetics of IO in the Photolysis of CH3I in the Presence of Ozone

Article abstract of DOI:10.1021/j100245a030

The photolysis of CH3I in the presence of O3 was used as a source of IO radicals in N2 + O2 diluent at 1-atm pressure and 303 K.IO was detected in absorption by using the molecular modulation technique.The absorption spectrum in the region 415-470 nm, arising from the A²Π <- X²Π transition of IO, was recorded and the absolute absorption cross section at the band head of the (4-0) band at 426.9 nm determined to be 3.1^+2.0_-1.5x10^-17 cm² molecule^-1.IO decayed by a rapid reaction which yielded an aerosol of probable formula I4O9 as a final product.The observed rate coefficient for IO decay was near the gas kinetic collision rate which probably reflects an efficient attachment of IO radicals to the growing aerosol.The significance of the photochemical and kinetic parameters for atmospheric iodine chemistry is briefly discussed.