1. Research & Advanced Engineering, Ford Motor Company, Mail Drop RIC-2122, Dearborn, Michigan 48121-2053, USA
2. Department of Chemistry and Biochemistry, California State University Northridge, 18111 Nordhoff St., Northridge, CA 91330-8262, USA
3. Copenhagen Center for Atmospheric Research, Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark