Neutral molecular cluster formation of sulfuric acid-dimethylamine observed in real time under atmospheric conditions

Andreas Kürten, Tuija Jokinen, Mario Simon, Mikko Sipilä, Nina Sarnela, Heikki Junninen, Alexey Adamov, João Almeida, Antonio Amorim, Federico Bianchi, Martin Breitenlechner, Josef Dommen, Neil M. Donahue, Jonathan Duplissy, Sebastian Ehrhart, Richard C. Flagan, Alessandro Franchin, Jani Hakala, Armin Hansel, Martin HeinritziManuel Hutterli, Juha Kangasluoma, Jasper Kirkby, Ari Laaksonen, Katrianne Lehtipalo, Markus Leiminger, Vladimir Makhmutov, Serge Mathot, Antti Onnela, Tuukka Petäjä, Arnaud P. Praplan, Francesco Riccobono, Matti P. Rissanen, Linda Rondo, Siegfried Schobesberger, John H. Seinfeld, Gerhard Steiner, António Tomé, Jasmin Tröstl, Paul M. Winkler, Christina Williamson, Daniela Wimmer, Penglin Ye, Urs Baltensperger, Kenneth S. Carslaw, Markku Kulmala, Douglas R. Worsnop, Joachim Curtius

Research output: Contribution to journalArticleScientificpeer-review

195 Citations (Scopus)


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 comparedwith 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.

Original languageEnglish
Pages (from-to)15019-15024
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number42
Publication statusPublished - 21 Oct 2014
MoE publication typeA1 Journal article-refereed


  • Aerosol particles
  • Atmospheric chemistry
  • Atmospheric nucleation
  • Mass spectrometry


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