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Physico-chemical parameters: the UV-visible absorption cross-sections of IONO2

The UV-visible absorption spectrum of gaseous iodine nitrate (IONO2) has been measured over the wavelength range 245 - 415nm, using the technique of laser photolysis with time-resolved UV-visible absorption spectroscopy. Atmospheric iodine source gases are readily photolysed by sunlight yielding iodine atoms, which react with ozone to form IO. Subsequent reactions of IO can lead to catalytic ozone loss. In competition, IO can be removed into reservoir species. For example, IONO2 can be formed via reaction with nitrogen dioxide.

The absorption coefficient of IONO2 is required in determining its atmospheric processing. The results indicate that IONO2 will have a photochemical lifetime of less than 1 minute under most sunlit conditions. Hence, IONO2 is not expected to act as a stable reservoir of atmospheric iodine during the day. Physico-chemical parameters, such as the IONO2 absorption cross-section, are used in models of atmospheric chemistry to gain understanding of atmospheric composition, and climate, at present and in the future. The IONO2 absorption cross-section data, measured here, is widely available to scientists due to dissemination of our results in an international journal

Citation: Mossinger, J.C., D.M. Rowley and R.A. Cox, The UV-visible absorption cross-sections of IONO2, Atmos. Chem. Phys., 2, 227-234, 2002

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