Kinetics study of the reactions IO + NO2 + M .fwdarw. IONO2 + M, IO + IO .fwdarw. products, and atomic iodine + ozone .fwdarw. iodine oxide (IO) + molecular oxygen

Abstract

A photochemical modulation technique was employed to investigate the title reactions. IO radicals were monitored in absorption at 426.9 nm where the absorption cross section at this wavelength was determined to be (2.2 +/- 0.5) x 10/sup -17/ cm/sup 2/ molecule/sup -1/. The reaction IO + NO/sub 2/ + M ..-->.. IONO/sub 2/ + M, studied between 35 and 404 torr at 277 K, was found to be in the falloff region between second- and third-order kinetics for this pressure range. The self-reaction IO + IO ..-->.. products was investigated between 10 and 100 torr at 303 K and between 25 and 404 torr at 277 K. The reaction appeared to proceed by at least two pathways, one pressure dependent and the other pressure independent. The results also allowed an estimate of (9.6 +/- 3.0) x 10/sup -13/ cm/sup 3/ molecule/sup -1/ s/sup -1/ for the rate coefficient of the reaction I + O/sub 3/ ..-->.. IO + O/sub 2/ at 26 torr and 303 K. 16 references, 10 figures, 4 tables.