Halogens and polar boundary-layer ozone depletion

1 Geophysical Institute and Department of Chemistry, University of Alaska Fairbanks, Fairbanks, AK, 99775-6160, USA 2 School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, UK 3 National Institute of Water and Atmospheric Research, Private Bag 14–901, Wellington, New Zealand 4 British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 0ET, UK 5 McGill University, Canada 6 Environment Canada, Toronto, Canada 7 Institute of Environmental Physics, University of Bremen, Bremen, Germany 8 Dept. of Chemistry, University of York , York YO10 5DD, UK 9 Institute for Environmental Physics, University of Heidelberg, Germany 10 University of Southern Denmark, Department of Chemistry and Physics, Campusvej 55 DK5230 Odense M, Denmark