Photodissociation of IO (355 nm) and OIO (532 nm): Quantum Yields for O(³P) and I(²P_J) Production

Abstract

The photodissociation of IO and OIO was investigated using 2-color, pulsed laser photolytic generation and dissociation of these species, combined with the detection of product atoms by resonance fluorescence. IO radicals were generated in the reactions of O(3P) with I2, O(3P) with CF3I, and I(2PJ) with O3 and were detected by absorption spectroscopy. The self-reaction of IO was used as the source of OIO, which was also detected by absorption spectroscopy. The quantum yield of O(3P) formation following the photolysis of IO at 355 nm was measured relative to NO2 photolysis at the same wavelength and was found to be 0.91 ± . O(3P) was not detected in the photolysis of OIO at 532 nm, enabling us to place an upper limit to the quantum yield of 7 × 10-3 at this wavelength. I(2PJ)was detected in the 532-nm photolysis of OIO but was formed only at very high laser fluence, presumably in a sequential two-photon process. These results show that OIO is probably stable with respect to photolysis in its strong visible absorption band between ≈480 and 660 nm, which has important implications for the iodine chemistry of the marine boundary layer.