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| Titel |
Amine reactivity with charged sulfuric acid clusters |
| VerfasserIn |
B. R. Bzdek, D. P. Ridge, M. V. Johnston |
| 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 ; 11, no. 16 ; Nr. 11, no. 16 (2011-08-26), S.8735-8743 |
| Datensatznummer |
250010032
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| Publikation (Nr.) |
 copernicus.org/acp-11-8735-2011.pdf |
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| Zusammenfassung |
| The distribution of charged species produced by electrospray of an ammonium
sulfate solution in both positive and negative polarities is examined using
Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS).
Positively-charged ammonium bisulfate cluster composition differs
significantly from negatively-charged cluster composition. For
positively-charged clusters all sulfuric acid is neutralized to bisulfate,
whereas for negatively-charged clusters the degree of sulfuric acid
neutralization is cluster size-dependent. With increasing cluster size (and,
therefore, a decreasing role of charge), both positively- and
negatively-charged cluster compositions converge toward ammonium bisulfate.
The reactivity of negatively-charged sulfuric acid-ammonia clusters with
dimethylamine and ammonia is also investigated by FTICR-MS. Two series of
negatively-charged clusters are investigated:
[(HSO4)(H2SO4)x]− and
[(NH4)x(HSO4)x+1(H2SO4)3]−.
Dimethylamine substitution for ammonia in
[(NH4) x(HSO4) x+1(H2SO4)3]− clusters
is nearly collision-limited, and subsequent addition of dimethylamine to
neutralize H2SO4 to bisulfate is within one order of magnitude of
the substitution rate. Dimethylamine addition to
[(HSO4) (H2SO4) x]− clusters is either not observed
or very slow. The results of this study indicate that amine chemistry will
be evident and important only in large ambient negative ions (>m/z 400),
whereas amine chemistry may be evident in small ambient positive ions.
Addition of ammonia to unneutralized clusters occurs at a rate that is ~2–3 orders of magnitude slower than incorporation of dimethylamine either
by substitution or addition. Therefore, in locations where amine levels are
within a few orders of magnitude of ammonia levels, amine chemistry may
compete favorably with ammonia chemistry. |
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