1. Department of Atmospheric and Oceanic Sciences and Laboratory for Atmospheric and Space Physics; University of Colorado at Boulder; Boulder, Colorado USA
2. Atmospheric Chemistry Division; National Center for Atmospheric Research; Boulder Colorado USA
3. Jet Propulsion Laboratory; California Institute of Technology; Pasadena California USA
4. Also at New Mexico Institute of Mining and Technology; Socorro New Mexico USA
5. Now at NorthWest Research Associates; Socorro New Mexico USA