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| Titel |
Quantum chemical studies on HSO5 - related nucleation |
| VerfasserIn |
T. Kurtén, T. Berndt, M. Toivola, H. Vehkamäki, F. Stratmann, M. Kulmala  |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250025683
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| Zusammenfassung |
| Recent laboratory experiments on SO2 and H2SO4 - based nucleation give reason to believe
that other sulfur - containing molecules than H2SO4 are likely to be involved in atmospheric
new-particle formation from SO2 oxidation in the presence of water. Specifically, reactions
involving HSO5 intermediate radicals have been proposed to give rise to products that
either nucleate more efficiently than H2SO4 + H2O, or enhance H2SO4 + H2O
nucleation.
We have used quantum chemical methods to study possible first steps of alternative
nucleation pathways in the SO2 oxidation process. Computed formation thermodynamics
indicate that a mixture of sulfuric acid with molecules containing more than one sulfur atom,
such as peroxydisulfuric acid, H2S2O8, is likely to nucleate more effective than sulfuric acid
on its own.
The central uncertainty in nucleation mechanisms involving HSO5 is the lifetime of this
metastable intermediate radical. Previous modeling studies have predicted the dissociation of
HSO5 into SO3 and HO2 to be very rapid, leading to a short lifetime of HSO5, and a low net
yield for the pathways forming alternative reaction products such as H2S2O8. However, these
studies have not accounted for the effect of hydration on the stability of HSO5. High-level
quantum chemical calculations demonstrate that HSO5 is much more strongly hydrated
than SO3 and HO2, leading to a significant increase in its lifetime with respect to
dissociation. At least partial proton transfer from HSO5 to H2O is predicted to occur in the
HSO5(H2O)2 cluster, which may have important implications for the reactivity of hydrated
HSO5. |
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