Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, 80309, USA

Department of Atmospheric and Oceanic Science, University of Colorado, Boulder, CO, 80309, USA

now at: School of Earth and Environment, University of Leeds, Leeds, UK

Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, 80309, USA

now at: College of Theology, Arts and Sciences, Concordia University, Portland, OR, 97211, USA

NASA Ames Research Center, Moffett Field, CA, USA

Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, 80309, USA

Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO, 80309, USA

Department of Chemistry, The Pennsylvania State University, 104 Chemistry Building, University Park, Pennsylvania 16802, USA

Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, 80309, USA

Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO, 80309, USA