1. Department of Chemistry, Texas Tech University, Lubbock, Texas 79409-1061, NOAA/Air Resources Laboratory, R/E/AR, SSMC3, 1315 East-West Highway, Silver Spring, Maryland 20910, U.S. EPA, MD-205-03, 109 Alexander Drive, Research Triangle Park, North Carolina 27711, Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, California 90095-1565, and Atmospheric Technology and Chemistry Divisions, National Center for Atmospheric Research, Boulder, Colorado 80303