1. Department of Chemistry; University of Toronto; Toronto Ontario Canada
2. Now at Department of Chemistry; Memorial University; St. John's Newfoundland and Labrador Canada
3. Now at Chemical Sciences Division, Earth System Research Laboratory; National Oceanic and Atmospheric Administration; Boulder Colorado USA
4. Now at Cooperative Institute for Research in Environmental Sciences; University of Colorado at Boulder; Boulder Colorado USA
5. Rosentiel School of Marine and Atmospheric Science; University of Miami; Miami Florida USA
6. Now at Air Resources Laboratory; National Oceanic and Atmospheric Administration; College Park Maryland USA
7. Department of Chemistry; University of California Berkeley; Berkeley California USA
8. Now at Department of Civil and Environmental Engineering; Massachusetts Institute of Technology; Cambridge Massachusetts USA
9. Department of Earth and Planetary Sciences; University of California Berkeley; Berkeley California USA
10. Department of Meteorology; Pennsylvania State University; University Park Pennsylvania USA