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| Titel |
The rate of water vapor evaporation from ice substrates in the presence of HCl and HBr: implications for the lifetime of atmospheric ice particles |
| VerfasserIn |
C. Delval, B. Fluckiger, M. J. Rossi |
| 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 ; 3, no. 4 ; Nr. 3, no. 4 (2003-08-01), S.1131-1145 |
| Datensatznummer |
250001144
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| Publikation (Nr.) |
 copernicus.org/acp-3-1131-2003.pdf |
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| Zusammenfassung |
| Using a
multidiagnostic approach the rate Rev [ molec cm-3 s-1]
or flux Jev [ molec cm-2 s-1] of
evaporation of H2O and its corresponding rate constant for
condensation, kcond [s-1 ], on a 1 µm thick ice
film have been studied in the temperature range 190 to 240 K as well as in
the presence of small amounts of HCl and HBr that left the vapor pressure
of H2O on ice unchanged. The resulting Arrhenius expressions
for pure ice are Jev = 1.6 · 10 28 ± 1 ·
exp (- 10.3 ± 1.2/ RT) [ molec cm-2 s-1]
, kcond = 1.7 · 10 - 2 ± 1 · exp (+ 1.6 ±
1.5/ RT ) [s -1], in the presence of a HCl mole fraction in the
range 3.2 · 10 - 5 - 6.4 · 10 - 3 : Jev
= 6.4 · 10 26 ± 1 · exp (- 9.7 ± 1.2/ RT) [
molec cm-2 s-1] , kcond = 2.8 · 10 -
2 ± 1 · exp ( + 1.5 ± 1.6 /RT) [s -1], and a HBr
mole fraction smaller than 6.4 · 10 - 3 : Jev = 7.4
· 10 25 ± 1 · exp ( - 9.1 ± 1.2 /RT) [ molec cm-2
s-1] , kcond = 7.1 · 10 - 5 ± 1 · exp
(+ 2.6 ± 1.5/ RT) [s -1]. The small negative activation energy
for H2O condensation on ice points to a precursor mechanism.
The corresponding enthalpy of sublimation is DHsubl
= Eev - Econd = 11.9 ± 2.7 kcal mol-1 , DHsubl
= 11.2 ± 2.8 kcal mol-1, and DHsubl
= 11.7 ± 2.8 kcal mol-1 whose values are identical within
experimental uncertainty to the accepted literature value of 12.3 kcal mol-1
. Interferometric data at 633 nm and FTIR absorption spectra in
transmission support the kinetic results. The data are consistent with a
significant lifetime enhancement for HCl- and HBr-contaminated ice
particles by a factor of 3–6 and 10–20, respectively, for submonolayer
coverages of HX once the fraction of the ice not contaminated by HX has
evaporated. |
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