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276615.0 [No comment] 19.09.2007 10:41 Released

ID: 276615.0, MPI für Kernphysik / Physics of Atmospheric Molecular Processes
Formation and growth of sulfuric acid-water cluster ions: Experiments, modelling, and implications for ion-induced aerosol formation
Authors:Sorokin, Andrey; Arnold, Frank; Wiedner, D.
Research Context:Cluster ions; Ion-induced nucleation; Aerosol formation
Date of Publication (YYYY-MM-DD):2006-04
Title of Journal:Atmospheric Environment
Issue / Number:11
Start Page:2030
End Page:2045
Copyright:© 2005 Elsevier
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:The formation, growth, and composition of mixed cluster ions HSO4-−AaWw and H+AaWw (A=H2SO4, W=H2O) with a up to 6 were investigated in the laboratory using a flow reactor-mass spectrometer apparatus. In the flow reactor the buffer gas (N2) pressure and temperature were kept constant at 80 hPa and 295 K, respectively, while the partial pressures of the trace gases H2SO4 and H2O and thereby also the relative humidity were varied. It was found that for small a (<5) positive ions are markedly enriched in H2O and negative ions are enriched in H2SO4 molecules. For larger a the composition of positive and negative ions becomes similar and approaches the modelled composition of a liquid AaWw droplet (respectively, for a>8 and a>15). When increasing the partial pressure of gaseous H2SO4 in the flow reactor both positive and negative ions grow via A uptake. This growth is more pronounced for negative ions where it becomes very efficient for a>8 reflecting A attachment to become faster than A detachment. We also have made model calculations indicating that for a>10 negative ion growth via A attachment occurs on nearly every collision of an A-molecule with an ion.
Free Keywords:Cluster ions; Ion-induced nucleation; Aerosol formation
External Publication Status:published
Document Type:Article
Affiliations:MPI für Kernphysik/Independent Research Groups/Atmospheric Trace Gas Environmental Physics (A. Arnold)
External Affiliations:IVTAN of the Russian Academy of Science, Krasnokazarmennaya 17a, 111116 Moscow, Russia