Determination of the evaporation coefficient of D2O W. S. Drisdell1,2, C. D. Cappa3, J. D. Smith2, R. J. Saykally1,2, and R. C. Cohen1,4 1Department of Chemistry, UC Berkeley, Berkeley, CA, USA 2Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA 3Department of Civil and Environmental Engineering, UC Davis, Davis, CA, USA 4Department of Earth and Planetary Science, UC Berkeley, Berkeley, CA, USA
Abstract. The evaporation rate of D2O has been determined by Raman thermometry of
a droplet train (12–15 μm diameter) injected into vacuum (~10-5 torr).
The cooling rate measured as a function of time in vacuum
was fit to a model that accounts for temperature gradients between the
surface and the core of the droplets, yielding an evaporation coefficient
(γe) of 0.57±0.06. This is nearly identical to that
found for H2O (0.62±0.09) using the same experimental method and
model, and indicates the existence of a kinetic barrier to evaporation. The
application of a recently developed transition-state theory (TST) model
suggests that the kinetic barrier is due to librational and hindered
translational motions at the liquid surface, and that the lack of an isotope
effect is due to competing energetic and entropic factors. The implications
of these results for cloud and aerosol particles in the atmosphere are
Citation: Drisdell, W. S., Cappa, C. D., Smith, J. D., Saykally, R. J., and Cohen, R. C.: Determination of the evaporation coefficient of D2O, Atmos. Chem. Phys., 8, 6699-6706, doi:10.5194/acp-8-6699-2008, 2008.