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

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( 3 P) with I 2, O( 3 P) with CF 3 I, and I( 2 P J ) with O 3 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( 3 P) formation following the photolysis of IO at 355 nm was measured relative to NO 2 photolysis at the same wavelength and was found to be 0.91 ± . O( 3 P) 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( 2 P J )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.