1. Earth System Research Laboratory, Chemical Sciences Division, National Oceanic and Atmospheric Administration, 325 Broadway, Boulder, Colorado 80305, United States
2. Department of Chemistry, University of North Texas, 1155 Union Circle Box 305070, Denton, Texas 76203-5070, United States
3. NASA Ames Research Center, Mountain View, California 94035, United States
4. BAER Institute, NASA Research Park, MS 18-4, Moffett Field, California 94035, United States
5. Department of Earth and Environmental Science and Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6316, United States