1. Atmospheric Chemistry Department (ACD), Leibniz Institute for Tropospheric Research (TROPOS), 04318 Leipzig, Germany
2. Institute for Ion Physics and Applied Physics, University of Innsbruck, 6020 Innsbruck, Austria
3. IONICON Analytik GmbH, 6020 Innsbruck, Austria
4. Nano and Molecular Systems Research Unit, University of Oulu, 90014 Oulu, Finland