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| Titel |
Atmospheric Oxidation of Carbonyl Sulfide and Associated Isotope Effect |
| VerfasserIn |
Johan A. Schmidt, Matthew S. Johnson, Sebastian Danielache |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250058133
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| Zusammenfassung |
| Carbonyl Sulfide (OCS) is the most abundant sulfur containing compound in the atmosphere. The main sinks for OCS in the atmosphere are reactions with HO and O(³P) and photolysis, with HO oxidation being the dominant sink [1]. Despite it’s importance there have only been a few studies of this reaction. Experimental studies limited to low pressures (p5 mbar) determined the reaction rate to be pressure independent with a rate of ca. k=2*10-15cm3s-1[2]. We present an ab initio theoretical study of the HO+OCS reaction. In the low pressure range (p10 mbar) we find that reaction is dominated by a pressure independent channel (b) where HO attacks the terminal S atom leading to SOH and CO. In this pressure range we calculate the rate to be k=2.4*10-15cm3s-1, in excellent agreement with experiments. Our study predicts that as the pressure is increased a complex forming channel (a) becomes important. Channel (a) is pressure dependent and exceeds channel (b) at pressures above ~500 mbar. At 1 bar we predict the overall rate to be k=6*10-15cm3s-1 or 3 times greater than previously known. In addition we have calculated the kinetic isotope effect. At low pressures where channel (b) dominates we predict the ³⁴S KIE to be about 20 permil and at higher pressures when channel (a) dominates the KIE is about 10 permil.
[1] E. Kjellstrom, J. Atm. Chem., 29, (1998), 151.
[2] B.-M. Cheng and Y.-P. Lee, Int. J. Chem. Kinet., 18, (1986), 1303 |
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