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| Titel |
Rate coefficients for the reaction of O(1D) with the atmospherically long-lived greenhouse gases NF3, SF5CF3, CHF3, C2F6, c-C4F8, n-C5F12, and n-C6F14 |
| VerfasserIn |
M. Baasandorj, B. D. Hall, J. B. Burkholder |
| 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 ; 12, no. 23 ; Nr. 12, no. 23 (2012-12-11), S.11753-11764 |
| Datensatznummer |
250011658
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| Publikation (Nr.) |
 copernicus.org/acp-12-11753-2012.pdf |
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| Zusammenfassung |
| The contribution of atmospherically persistent (long-lived) greenhouse gases
to the radiative forcing of Earth has increased over the past several
decades. The impact of highly fluorinated, saturated compounds, in particular
perfluorinated compounds, on climate change is a concern because of their
long atmospheric lifetimes, which are primarily determined by stratospheric
loss processes, as well as their strong absorption in the infrared "window"
region. A potentially key stratospheric loss process for these compounds is
their gas-phase reaction with electronically excited oxygen atoms,
O(1D). Therefore, accurate reaction rate coefficient data is desired for
input to climate change models. In this work, rate coefficients, k, were
measured for the reaction of O(1D) with several key long-lived
greenhouse gases, namely NF3, SF5CF3, CHF3 (HFC-23),
C2F6, c-C4F8, n-C5F12, and
n-C6F14. Room temperature rate coefficients for the total
reaction, kTot, corresponding to loss of O(1D), and reactive
channel, kR, corresponding to the loss of the reactant compound,
were measured for NF3 and SF5CF3 using competitive reaction
and relative rate methods, respectively. kR was measured for the
CHF3 reaction and improved upper-limits were determined for the
perfluorinated compounds included in this study. For NF3,
kTot was determined to be
(2.55 ± 0.38) × 10−11 cm3 molecule−1 s−1
and kR, which was measured using CF3Cl, N2O,
CF2ClCF2Cl (CFC-114), and CF3CFCl2 (CFC-114a) as
reference compounds, was determined to be
(2.21 ± 0.33) × 10−11 cm3 molecule−1 s−1.
For
SF5CF3, kTot = (3.24 ± 0.50) × 10−13 cm3 molecule−1 s−1
and kR < 5.8 × 10×14 cm3 molecule−1 s−1 were
measured, where kR is a factor of three lower than the current
recommendation of kTot for use in atmospheric modeling. For
CHF3 kR was determined to be
(2.35 ± 0.35) × 10−12 cm3 molecule−1 s−1,
which corresponds to a reactive channel yield of 0.26 ± 0.04, and
resolves a large discrepancy among previously reported values. The quoted
uncertainties are 2σ and include estimated systematic errors.
Upper-limits for kR for the C2F6, c-C4F8,
n-C5F12, and n-C6F14 reactions were
determined to be 3.0, 3.5, 5.0, and 16 (in units of
10−14 cm3 molecule−1 s−1), respectively. The results
from this work are compared with results from previous studies. As part of
this work, infrared absorption band strengths for NF3 and
SF5CF3 were measured and found to be in good agreement with
recently reported values. |
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