title: Neutral molecular cluster formation of sulfuric acid-dimethylamine observed in real time under atmospheric conditions.
abstract: For atmospheric sulfuric acid (SA) concentrations the presence of dimethylamine (DMA) at mixing ratios of several parts per trillion by volume can explain observed boundary layer new particle formation rates. However, the concentration and molecular composition of the neutral (uncharged) clusters have not been reported so far due to the lack of suitable instrumentation. Here we report on experiments from the Cosmics Leaving Outdoor Droplets chamber at the European Organization for Nuclear Research revealing the formation of neutral particles containing up to 14 SA and 16 DMA molecules, corresponding to a mobility diameter of about 2 nm, under atmospherically relevant conditions. These measurements bridge the gap between the molecular and particle perspectives of nucleation, revealing the fundamental processes involved in particle formation and growth. The neutral clusters are found to form at or close to the kinetic limit where particle formation is limited only by the collision rate of SA molecules. Even though the neutral particles are stable against evaporation from the SA dimer onward, the formation rates of particles at 1.7-nm size, which contain about 10 SA molecules, are up to 4 orders of magnitude smaller compared with those of the dimer due to coagulation and wall loss of particles before they reach 1.7 nm in diameter. This demonstrates that neither the atmospheric particle formation rate nor its dependence on SA can simply be interpreted in terms of cluster evaporation or the molecular composition of a critical nucleus.
authors.affiliation: Institute for Atmospheric and Environmental Sciences, Goethe-University of Frankfurt, 60438 Frankfurt am Main, Germany; kuerten@iau.uni-frankfurt.de.
authors.forename: Andreas
authors.initials: A
authors.lastname: Kürten
authors.affiliation: Department of Physics, University of Helsinki, 00014 Helsinki, Finland;
authors.forename: Tuija
authors.initials: T
authors.lastname: Jokinen
authors.affiliation: Institute for Atmospheric and Environmental Sciences, Goethe-University of Frankfurt, 60438 Frankfurt am Main, Germany;
authors.forename: Mario
authors.initials: M
authors.lastname: Simon
authors.affiliation: Department of Physics, University of Helsinki, 00014 Helsinki, Finland; Helsinki Institute of Physics, University of Helsinki, 00014 Helsinki, Finland;
authors.forename: Mikko
authors.initials: M
authors.lastname: Sipilä
authors.affiliation: Department of Physics, University of Helsinki, 00014 Helsinki, Finland;
authors.forename: Nina
authors.initials: N
authors.lastname: Sarnela
authors.affiliation: Department of Physics, University of Helsinki, 00014 Helsinki, Finland;
authors.forename: Heikki
authors.initials: H
authors.lastname: Junninen
authors.affiliation: Department of Physics, University of Helsinki, 00014 Helsinki, Finland;
authors.forename: Alexey
authors.initials: A
authors.lastname: Adamov
authors.affiliation: Institute for Atmospheric and Environmental Sciences, Goethe-University of Frankfurt, 60438 Frankfurt am Main, Germany; European Organization for Nuclear Research, CH-1211 Geneva, Switzerland;
authors.forename: João
authors.initials: J
authors.lastname: Almeida
authors.affiliation: Laboratory for Systems, Instrumentation and Modeling for Space and the Environment, University of Lisbon and University of Beira Interior, 1749-016 Lisbon, Portugal;
authors.forename: Antonio
authors.initials: A
authors.lastname: Amorim
authors.affiliation: Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland;
authors.forename: Federico
authors.initials: F
authors.lastname: Bianchi
authors.affiliation: Ionicon Analytik GmbH, 6020 Innsbruck, Austria; Institute for Ion Physics and Applied Physics, University of Innsbruck, 6020 Innsbruck, Austria;
authors.forename: Martin
authors.initials: M
authors.lastname: Breitenlechner
authors.affiliation: Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland;
authors.forename: Josef
authors.initials: J
authors.lastname: Dommen
authors.affiliation: Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, PA 15213;
authors.forename: Neil M
authors.initials: NM
authors.lastname: Donahue
authors.affiliation: Department of Physics, University of Helsinki, 00014 Helsinki, Finland; Helsinki Institute of Physics, University of Helsinki, 00014 Helsinki, Finland; European Organization for Nuclear Research, CH-1211 Geneva, Switzerland;
authors.forename: Jonathan
authors.initials: J
authors.lastname: Duplissy
authors.affiliation: Institute for Atmospheric and Environmental Sciences, Goethe-University of Frankfurt, 60438 Frankfurt am Main, Germany; European Organization for Nuclear Research, CH-1211 Geneva, Switzerland;
authors.forename: Sebastian
authors.initials: S
authors.lastname: Ehrhart
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125;
authors.forename: Richard C
authors.initials: RC
authors.lastname: Flagan
authors.affiliation: Department of Physics, University of Helsinki, 00014 Helsinki, Finland;
authors.forename: Alessandro
authors.initials: A
authors.lastname: Franchin
authors.affiliation: Department of Physics, University of Helsinki, 00014 Helsinki, Finland;
authors.forename: Jani
authors.initials: J
authors.lastname: Hakala
authors.affiliation: Ionicon Analytik GmbH, 6020 Innsbruck, Austria; Institute for Ion Physics and Applied Physics, University of Innsbruck, 6020 Innsbruck, Austria;
authors.forename: Armin
authors.initials: A
authors.lastname: Hansel
authors.affiliation: Institute for Atmospheric and Environmental Sciences, Goethe-University of Frankfurt, 60438 Frankfurt am Main, Germany; Institute for Ion Physics and Applied Physics, University of Innsbruck, 6020 Innsbruck, Austria;
authors.forename: Martin
authors.initials: M
authors.lastname: Heinritzi
authors.affiliation: Tofwerk AG, 3600 Thun, Switzerland;
authors.forename: Manuel
authors.initials: M
authors.lastname: Hutterli
authors.affiliation: Department of Physics, University of Helsinki, 00014 Helsinki, Finland;
authors.forename: Juha
authors.initials: J
authors.lastname: Kangasluoma
authors.affiliation: Institute for Atmospheric and Environmental Sciences, Goethe-University of Frankfurt, 60438 Frankfurt am Main, Germany; European Organization for Nuclear Research, CH-1211 Geneva, Switzerland;
authors.forename: Jasper
authors.initials: J
authors.lastname: Kirkby
authors.affiliation: Department of Applied Physics, University of Eastern Finland, 70211 Kuopio, Finland; Finnish Meteorological Institute, 00101 Helsinki, Finland;
authors.forename: Ari
authors.initials: A
authors.lastname: Laaksonen
authors.affiliation: Department of Physics, University of Helsinki, 00014 Helsinki, Finland; Airmodus Ltd., 00560 Helsinki, Finland;
authors.forename: Katrianne
authors.initials: K
authors.lastname: Lehtipalo
authors.affiliation: Institute for Atmospheric and Environmental Sciences, Goethe-University of Frankfurt, 60438 Frankfurt am Main, Germany;
authors.forename: Markus
authors.initials: M
authors.lastname: Leiminger
authors.affiliation: Solar and Cosmic Ray Research Laboratory, Lebedev Physical Institute, 119991 Moscow, Russia;
authors.forename: Vladimir
authors.initials: V
authors.lastname: Makhmutov
authors.affiliation: European Organization for Nuclear Research, CH-1211 Geneva, Switzerland;
authors.forename: Serge
authors.initials: S
authors.lastname: Mathot
authors.affiliation: European Organization for Nuclear Research, CH-1211 Geneva, Switzerland;
authors.forename: Antti
authors.initials: A
authors.lastname: Onnela
authors.affiliation: Department of Physics, University of Helsinki, 00014 Helsinki, Finland;
authors.forename: Tuukka
authors.initials: T
authors.lastname: Petäjä
authors.affiliation: Department of Physics, University of Helsinki, 00014 Helsinki, Finland;
authors.forename: Arnaud P
authors.initials: AP
authors.lastname: Praplan
authors.affiliation: Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland;
authors.forename: Francesco
authors.initials: F
authors.lastname: Riccobono
authors.affiliation: Department of Physics, University of Helsinki, 00014 Helsinki, Finland;
authors.forename: Matti P
authors.initials: MP
authors.lastname: Rissanen
authors.affiliation: Institute for Atmospheric and Environmental Sciences, Goethe-University of Frankfurt, 60438 Frankfurt am Main, Germany;
authors.forename: Linda
authors.initials: L
authors.lastname: Rondo
authors.affiliation: Department of Physics, University of Helsinki, 00014 Helsinki, Finland;
authors.forename: Siegfried
authors.initials: S
authors.lastname: Schobesberger
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125;
authors.forename: John H
authors.initials: JH
authors.lastname: Seinfeld
authors.affiliation: Department of Physics, University of Helsinki, 00014 Helsinki, Finland; Institute for Ion Physics and Applied Physics, University of Innsbruck, 6020 Innsbruck, Austria;
authors.forename: Gerhard
authors.initials: G
authors.lastname: Steiner
authors.affiliation: Laboratory for Systems, Instrumentation and Modeling for Space and the Environment, University of Lisbon and University of Beira Interior, 1749-016 Lisbon, Portugal;
authors.forename: António
authors.initials: A
authors.lastname: Tomé
authors.affiliation: Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland;
authors.forename: Jasmin
authors.initials: J
authors.lastname: Tröstl
authors.affiliation: Faculty of Physics, University of Vienna, 1090 Vienna, Austria;
authors.forename: Paul M
authors.initials: PM
authors.lastname: Winkler
authors.affiliation: Institute for Atmospheric and Environmental Sciences, Goethe-University of Frankfurt, 60438 Frankfurt am Main, Germany;
authors.forename: Christina
authors.initials: C
authors.lastname: Williamson
authors.affiliation: Institute for Atmospheric and Environmental Sciences, Goethe-University of Frankfurt, 60438 Frankfurt am Main, Germany; Department of Physics, University of Helsinki, 00014 Helsinki, Finland;
authors.forename: Daniela
authors.initials: D
authors.lastname: Wimmer
authors.affiliation: Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, PA 15213;
authors.forename: Penglin
authors.initials: P
authors.lastname: Ye
authors.affiliation: Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland;
authors.forename: Urs
authors.initials: U
authors.lastname: Baltensperger
authors.affiliation: School of Earth and Environment, University of Leeds, Leeds LS2 9JT, United Kingdom; and.
authors.forename: Kenneth S
authors.initials: KS
authors.lastname: Carslaw
authors.affiliation: Department of Physics, University of Helsinki, 00014 Helsinki, Finland; Helsinki Institute of Physics, University of Helsinki, 00014 Helsinki, Finland;
authors.forename: Markku
authors.initials: M
authors.lastname: Kulmala
authors.affiliation: Department of Physics, University of Helsinki, 00014 Helsinki, Finland; Aerodyne Research Inc., Billerica, MA 01821.
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Worsnop
authors.affiliation: Institute for Atmospheric and Environmental Sciences, Goethe-University of Frankfurt, 60438 Frankfurt am Main, Germany;
authors.forename: Joachim
authors.initials: J
authors.lastname: Curtius
keywords: aerosol particles; atmospheric chemistry; atmospheric nucleation; mass spectrometry