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| Titel |
Electrical charging changes the composition of sulfuric acid–ammonia/dimethylamine clusters |
| VerfasserIn |
I. K. Ortega, T. Olenius, O. Kupiainen-Määttä, V. Loukonen, T. Kurtén, H. Vehkamäki |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 14, no. 15 ; Nr. 14, no. 15 (2014-08-12), S.7995-8007 |
| Datensatznummer |
250118936
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| Publikation (Nr.) |
 copernicus.org/acp-14-7995-2014.pdf |
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| Zusammenfassung |
| Sulfuric acid clusters stabilized by base molecules are likely to have a
significant role in atmospheric new-particle formation. Recent advances in
mass spectrometry techniques have permitted the detection of electrically
charged clusters. However, direct measurement of electrically neutral
clusters is not possible. Mass spectrometry instruments can be combined with
a charger, but the possible effect of charging on the composition of neutral
clusters must be addressed in order to interpret and understand the measured
data. In the present work we have used formation free energies from quantum
chemical methods to calculate the evaporation rates of electrically charged
(both positive and negative) sulfuric acid–ammonia/dimethylamine clusters.
To understand how charging will affect the composition of electrically
neutral clusters, we have compared the evaporation rates of the most stable
neutral clusters with those of the corresponding charged clusters. Based on
the evaporation rates of different molecules from the charged clusters, we
determined the most likely resulting cluster composition when a stable
neutral cluster is charged and the molecules with the highest evaporation
rates are lost from it. We found that all of the most stable neutral
clusters will be altered by both positive and negative charging. In the case
of charging clusters negatively, base molecules will completely evaporate
from clusters with 1 to 3 sulfuric acid molecules in the case of ammonia,
and from clusters with 1 or 2 sulfuric acid molecules in the case of
dimethylamine. Larger clusters will maintain some base molecules, but the
H2SO4 : base ratio will increase. In the case of positive charging,
some of the acid molecules will evaporate, decreasing the
H2SO4 : base ratio. |
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