ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-4-19-2004 Laboratory studies of the homogeneous nucleation of iodine oxides Burkholder J. B. 1 Curtius J. 1 2 Ravishankara A. R. 1 3 Lovejoy E. R. 1 Aeronomy Laboratory, National Oceanic and Atmospheric Administration, 325 Broadway, Boulder, CO 80305-3328, USA now at: Institute for Atmospheric Physics, Mainz University, Mainz, Germany also associated with the Dept. of Chemistry and Biochemistry, Uuniversity of Colorado, Boulder, CO 80309, USA 20 01 2004 4 1 19 34 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/4/19/2004/acp-4-19-2004.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/4/19/2004/acp-4-19-2004.pdf

Laboratory experimental results of iodine oxide nucleation are presented. Nucleation was induced following UV photolysis of CF<sub>3</sub>I or CH<sub>2</sub>I<sub>2</sub> in the presence of excess ozone. Measurements were performed in a 70 L Teflon reactor with new particles detected using an Ultrafine Condensation Particle Counter, UCPC. The experimental results are interpreted using a coupled chemical - aerosol model to derive model parameters assuming single component homogeneous nucleation of OIO. The aerosol model results have been applied in an atmospheric box-model to interpret the possible implications of iodine oxide nucleation in the marine boundary layer. The model calculations demonstrate that IO and OIO concentrations reported in recent field measurements using long path absorption (Allan et al., 2000, 2001) are not sufficient to account for significant aerosol production either in the coastal or open ocean marine boundary layer using the mechanism presented. We demonstrate that inhomogeneous sources of iodine oxides, i.e. &quot;hot&quot; spots with elevated iodine species emissions, could account for the aerosol production bursts observed in the coastal region near Mace Head, Ireland.