title: The effect of acid-base clustering and ions on the growth of atmospheric nano-particles.
abstract: The growth of freshly formed aerosol particles can be the bottleneck in their survival to cloud condensation nuclei. It is therefore crucial to understand how particles grow in the atmosphere. Insufficient experimental data has impeded a profound understanding of nano-particle growth under atmospheric conditions. Here we study nano-particle growth in the CLOUD (Cosmics Leaving OUtdoors Droplets) chamber, starting from the formation of molecular clusters. We present measured growth rates at sub-3 nm sizes with different atmospherically relevant concentrations of sulphuric acid, water, ammonia and dimethylamine. We find that atmospheric ions and small acid-base clusters, which are not generally accounted for in the measurement of sulphuric acid vapour, can participate in the growth process, leading to enhanced growth rates. The availability of compounds capable of stabilizing sulphuric acid clusters governs the magnitude of these effects and thus the exact growth mechanism. We bring these observations into a coherent framework and discuss their significance in the atmosphere.
authors.affiliation: Department of Physics, University of Helsinki, PO Box 64, 00014 Helsinki, Finland.|Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland.
authors.forename: Katrianne
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authors.lastname: Lehtipalo
authors.affiliation: Institute for Atmospheric and Environmental Sciences, Goethe-University of Frankfurt, Altenhöferallee 1, 60438 Frankfurt am Main, Germany.
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authors.lastname: Rondo
authors.affiliation: Department of Physics, University of Helsinki, PO Box 64, 00014 Helsinki, Finland.
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authors.lastname: Sarnela
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authors.affiliation: Institute for Atmospheric and Environmental Sciences, Goethe-University of Frankfurt, Altenhöferallee 1, 60438 Frankfurt am Main, Germany.|CERN, 1211 Geneva, Switzerland.
authors.forename: Sebastian
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authors.lastname: Ehrhart
authors.affiliation: Department of Physics, University of Helsinki, PO Box 64, 00014 Helsinki, Finland.
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authors.affiliation: Department of Physics, University of Helsinki, PO Box 64, 00014 Helsinki, Finland.|Helsinki Institute of Physics, University of Helsinki, PO Box 64, 00014 Helsinki, Finland.
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authors.lastname: Nieminen
authors.affiliation: Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland.
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authors.lastname: Sipilä
authors.affiliation: Department of Physics, University of Helsinki, PO Box 64, 00014 Helsinki, Finland.|Department of Applied Physics, University of Eastern Finland, PO Box 1627, 70211 Kuopio, Finland.
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authors.lastname: Yli-Juuti
authors.affiliation: Department of Physics, University of Helsinki, PO Box 64, 00014 Helsinki, Finland.|CERN, 1211 Geneva, Switzerland.|Helsinki Institute of Physics, University of Helsinki, PO Box 64, 00014 Helsinki, Finland.
authors.forename: Jonathan
authors.identifier: 0000-0001-8819-0264
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authors.lastname: Duplissy
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authors.affiliation: Department of Environmental Science and Analytical Chemistry (ACES) &Bolin Centre for Climate Research, Stockholm University, 10691 Stockholm, Sweden.
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authors.lastname: Ahlm
authors.affiliation: CERN, 1211 Geneva, Switzerland.|SIM, University of Lisbon and University of Beira Interior, 1749-016 Lisbon, Portugal.
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authors.lastname: Almeida
authors.affiliation: SIM, University of Lisbon and University of Beira Interior, 1749-016 Lisbon, Portugal.
authors.forename: Antonio
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authors.lastname: Amorim
authors.affiliation: Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland.|Institute for Atmospheric and Climate Science, ETH Zurich, 8092 Zurich, Switzerland.
authors.forename: Federico
authors.identifier: 0000-0003-2996-3604
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authors.affiliation: Institute for Ion Physics and Applied Physics, Technikerstraße 25, 6020 Innsbruck, Austria.
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authors.affiliation: Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland.
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authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Boulevard Pasadena, California 91125, USA.
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authors.affiliation: Institute for Ion Physics and Applied Physics, Technikerstraße 25, 6020 Innsbruck, Austria.|Ionicon Analytik GmbH, Eduard-Bodem-Gasse 3, 6020 Innsbruck, Austria.
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authors.affiliation: Department of Physics, University of Helsinki, PO Box 64, 00014 Helsinki, Finland.|Department of Applied Physics, University of Eastern Finland, PO Box 1627, 70211 Kuopio, Finland.|Finnish Meteorological Institute, Atmospheric Research Centre of Eastern Finland, PO Box 1627, 70211 Kuopio, Finland.|Aerodyne Research Inc., Billerica, Massachusetts 01821-3976, USA.
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