1. Department of Chemistry and Biochemistry and Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder, Boulder, Colorado.
2. Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder, Boulder, Colorado.
3. Space Science Division, NASA Ames Research Center, Moffett Field, California.
4. Aerodyne Research Inc., Billerica, Massachusetts.
5. Program in Atmospheric and Oceanic Sciences, University of Colorado at Boulder, Boulder, Colorado.
6. Laboratory for Atmospheric and Space Physics and Program in Atmospheric and Oceanic Sciences, University of Colorado at Boulder, Boulder, Colorado.