1. Laboratory of Environmental Chemistry, Paul Scherrer Institut, 5232 Villigen, Switzerland
2. Institute of Atmospheric and Climate Science, ETH Zürich, 8092 Zürich, Switzerland
3. Department of Chemistry and Molecular Biology, University of Gothenburg, 41296 Gothenburg, Sweden
4. Institute for Chemical and Bioengineering, ETH Zürich, 8093 Zürich, Switzerland