EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

The first steps of iodine gas-to-particle conversion as seen in the lab: constraints on the role of iodine oxides and oxyacids

Juan Carlos Gomez Martin1, Tom Lewis2, Manoj Kumar3, John Plane4, Joseph Francisco3, and Alfonso Saiz-Lopez2
Juan Carlos Gomez Martin et al.
  • 1Instituto de Astrofisica de Andalucia - CSIC, Solar System Department, Granada, Spain (
  • 2Department of Atmospheric Chemistry and Climate, Institute of Physical Chemistry Rocasolano, CSIC, Madrid, Spain
  • 3University of Pennsylvania, School of Arts and Sciences, Department of Chemistry, Philadelphia, PA 19104-6323, USA
  • 4 School of Chemistry, University of Leeds, LS2 9JT Leeds, UK

The photooxidation of gas phase iodine-bearing molecules emitted by marine biota leads to intense particle nucleation events in the coastal and polar marine boundary layer1-3. The ubiquity of iodine in the marine atmospheric environment4-7 has suggested that this may be a previously unrecognized global source of new aerosol particles8. Atmospheric modeling is required in order to evaluate the importance of this process, but a substantial lack of understanding of the gas-to-particle conversion mechanism is hindering this effort, especially regarding the gas phase chemistry of the nucleating molecules (iodine oxides9,10 and/or oxyacids7) and the formation kinetics of molecular clusters. To address this problem, we have conducted new flow tube laboratory experiments where pulsed laser photolysis or continuous broad-band photolysis of I2/O3 mixtures  in air are used to generate iodine radicals in the presence of atmospherically representative mixing ratios of water vapor. The molecular reactants and the resulting molecular products are detected by time-resolved VUV laser photo-ionization time-of-flight mass spectrometry. High-level quantum chemistry and master equation calculations and gas kinetics modelling are used to analyse the experimental data. In this presentation we discuss our results and their implications for the interpretation of field meassurements and for the implementatiion of an iodine oxide particle formation mechanism in atmospheric models.


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How to cite: Gomez Martin, J. C., Lewis, T., Kumar, M., Plane, J., Francisco, J., and Saiz-Lopez, A.: The first steps of iodine gas-to-particle conversion as seen in the lab: constraints on the role of iodine oxides and oxyacids, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2870,, 2020