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The Kinetics of H2O Vapor Condensation and Evaporation on Different Types of Ice in the Range 130−210 K

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journal contribution
posted on 2006-03-09, 00:00 authored by Pascal Pratte, Hubert van den Bergh, Michel J. Rossi
The kinetics of condensation (kc) and the evaporation flux (Jev) of H2O on ice were studied in the range 130−210 K using pulsed-valve and steady-state techniques in a low-pressure flow reactor. The uptake coefficient γ was measured for different types of ice, namely, condensed (C), bulk (B), single crystal (SC), snow (S), and cubic ice (K). The negative temperature dependence of γ for C, B, SC, and S ice reveals a precursor-mediated adsorption/desorption process in agreement with the proposal of Davy and Somorjai. The non-Arrhenius behavior of the rate of condensation, kc, manifests itself in a discontinuity in the range 170−190 K depending on the type of ice and is consistent with the precursor model. The average of the energy of sublimation ΔHS° is (12.0 ± 1.4) kcal/mol for C, B, S, and SC ice and is identical within experimental uncertainty between 136 and 210 K. The same is true for the entropy of sublimation ΔSS. In contrast, both γ and the evaporative flux Jev are significantly different for different ices. In the range 130−210 K, Jev of H2O ice was significantly smaller than the maximum theoretically allowed value. This corroborates γ values significantly smaller than unity in that T range. On the basis of the present kinetic parameters, the time to complete evaporation of a small ice particle of radius 1 μm is approximately a factor of 5 larger than that previously thought.