The rate of water vapor evaporation from ice substrates in the presence of HCl and HBr: implications for the lifetime of atmospheric ice particles
Item
Title (Dublin Core)
The rate of water vapor evaporation from ice substrates in the presence of HCl and HBr: implications for the lifetime of atmospheric ice particles
Description (Dublin Core)
Using a multidiagnostic approach the rate Rev [ molec cm<sup>-3</sup> s<sup>-1</sup>] or flux J<sub>ev</sub> [ molec cm<sup>-2</sup> s<sup>-1</sup>] of evaporation of H<sub>2</sub>O and its corresponding rate constant for condensation, k<sub>cond</sub> [s<sup>-1</sup> ], 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 H<sub>2</sub>O on ice unchanged. The resulting Arrhenius expressions for pure ice are J<sub>ev</sub> = 1.6 · 10 <sup>28 ± 1</sup> · exp (- 10.3 ± 1.2/ RT) [ molec cm<sup>-2</sup> s<sup>-1</sup>] , k<sub>cond</sub> = 1.7 · 10 <sup>- 2 ± 1</sup> · exp (+ 1.6 ± 1.5/ RT ) [s <sup>-1</sup>], in the presence of a HCl mole fraction in the range 3.2 · 10 <sup>- 5</sup> - 6.4 · 10 <sup>- 3</sup> : J<sub>ev</sub> = 6.4 · 10 <sup>26 ± 1</sup> · exp (- 9.7 ± 1.2/ RT) [ molec cm<sup>-2</sup> s<sup>-1</sup>] , k<sub>cond</sub> = 2.8 · 10 <sup>- 2 ± 1</sup> · exp ( + 1.5 ± 1.6 /RT) [s <sup>-1</sup>], and a HBr mole fraction smaller than 6.4 · 10 <sup>- 3</sup> : J<sub>ev</sub> = 7.4 · 10 <sup>25 ± 1</sup> · exp ( - 9.1 ± 1.2 /RT) [ molec cm<sup>-2</sup> s<sup>-1</sup>] , k<sub>cond</sub> = 7.1 · 10 <sup>- 5 ± 1</sup> · exp (+ 2.6 ± 1.5/ RT) [s <sup>-1</sup>]. The small negative activation energy for H<sub>2</sub>O condensation on ice points to a precursor mechanism. The corresponding enthalpy of sublimation is <font face="Symbol">D</font>H<sub>subl</sub> = E<sub>ev</sub> - E<sub>cond</sub> = 11.9 ± 2.7 kcal mol<sup>-1</sup> , <font face="Symbol">D</font>H<sub>subl</sub> = 11.2 ± 2.8 kcal mol<sup>-1</sup>, and <font face="Symbol">D</font>H<sub>subl</sub> = 11.7 ± 2.8 kcal mol<sup>-1</sup> whose values are identical within experimental uncertainty to the accepted literature value of 12.3 kcal mol<sup>-1</sup> . 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.
Creator (Dublin Core)
Delval, C.
Fluckiger, B.
Rossi, M. J.
Date (Dublin Core)
2018-06-29
Type (Dublin Core)
Text
Format (Dublin Core)
application/pdf
Identifier (Dublin Core)
10.5194/acp-3-1131-2003
https://acp.copernicus.org/articles/3/1131/2003/
Source (Dublin Core)
eISSN: 1680-7324
Language (Dublin Core)
eng
