1. Chemical Sciences Division; NOAA Earth System Research Laboratory; Boulder Colorado USA
2. Cooperative Institute for Research in Environmental Sciences; University of Colorado Boulder; Boulder Colorado USA
3. Department of Civil and Environmental Engineering; University of California; Berkeley California USA
4. Department of Chemistry and Biochemistry; University of Colorado Boulder; Boulder Colorado USA
5. NASA Langley Research Center; Hampton Virginia USA
6. Now at Aerodyne Research, Inc.; Billerica Massachusetts USA
7. Now at Department of Atmospheric Science and Department of Chemistry; Colorado State University; Fort Collins Colorado USA
8. Now at Department of Chemistry; Memorial University; St. John's Newfoundland and Labrador Canada