CERN Accelerating science

Article
Report number	arXiv:1509.03474
Title	Neutral molecular cluster formation of sulfuric acid–dimethylamine observed in real time under atmospheric conditions
Author(s)	Kürten, Andreas (Goethe U., Frankfurt (main)) ; Jokinen, Tuija (Helsinki U.) ; Simon, Mario (Goethe U., Frankfurt (main)) ; Sipilä, Mikko (Helsinki U. ; Helsinki Inst. of Phys.) ; Sarnela, Nina (Helsinki U.) ; Junninen, Heikki (Helsinki U.) ; Adamov, Alexey (Helsinki U.) ; Almeida, João (Goethe U., Frankfurt (main) ; CERN) ; Amorim, Antonio (UBI, Covilha ; U. Lisbon (main)) ; Bianchi, Federico (PSI, Villigen) ; Breitenlechner, Martin (Ionicon Analytik, Innsburk ; Innsbruck U.) ; Dommen, Josef (PSI, Villigen) ; Donahue, Neil M (Carnegie Mellon U. (main)) ; Duplissy, Jonathan (Helsinki U. ; Helsinki Inst. of Phys. ; CERN) ; Ehrhart, Sebastian (Goethe U., Frankfurt (main) ; CERN) ; Flagan, Richard C (Caltech, Pasadena (main)) ; Franchin, Alessandro (Helsinki U.) ; Hakala, Jani (Helsinki U.) ; Hansel, Armin (Ionicon Analytik, Innsburk ; Innsbruck U.) ; Heinritzi, Martin (Goethe U., Frankfurt (main) ; Innsbruck U.) ; Hutterli, Manuel (Tofwerk, Thun) ; Kangasluoma, Juha (Helsinki U.) ; Kirkby, Jasper (Goethe U., Frankfurt (main) ; CERN) ; Laaksonen, Ari (UEF, Kuopio ; Finnish Meteorological Inst.) ; Lehtipalo, Katrianne (Helsinki U. ; Airmodus, Helsinki) ; Leiminger, Markus (Goethe U., Frankfurt (main)) ; Makhmutov, Vladimir (LPI, Moscow (main)) ; Mathot, Serge (CERN) ; Onnela, Antti (CERN) ; Petäjä, Tuukka (Helsinki U.) ; Praplan, Arnaud P (Helsinki U.) ; Riccobono, Francesco (PSI, Villigen) ; Rissanen, Matti P (Helsinki U.) ; Rondo, Linda (Goethe U., Frankfurt (main)) ; Schobesberger, Siegfried (Helsinki U.) ; Seinfeld, John H (Caltech, Pasadena (main)) ; Steiner, Gerhard (Helsinki U. ; Innsbruck U.) ; Tomé, António (U. Lisbon (main) ; UBI, Covilha) ; Tröstl, Jasmin (PSI, Villigen) ; Winkler, Paul M (U. Vienna (main)) ; Williamson, Christina (Goethe U., Frankfurt (main)) ; Wimmer, Daniela (Goethe U., Frankfurt (main) ; Helsinki U.) ; Ye, Penglin (Carnegie Mellon U. (main)) ; Baltensperger, Urs (PSI, Villigen) ; Carslaw, Kenneth S (U. Leeds (main)) ; Kulmala, Markku (Helsinki U. ; Helsinki Inst. of Phys.) ; Worsnop, Douglas R (Helsinki U.) ; Curtius, Joachim (Goethe U., Frankfurt (main))
Publication	2014
Note	Comments: Main text plus SI
In:	Proc. Natl. Acad. Sci. U.S.A. 111 (2014) 15019-15024
DOI	10.1073/pnas.1404853111
Subject category	Chemical Physics and Chemistry
Accelerator/Facility, Experiment	CERN PS ; CLOUD PS215
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.
Copyright/License	arXiv nonexclusive-distrib. 1.0