Temperature discontinuity at the surface of an evaporating droplet

In a series of experiments, a temperature discontinuity has been found to exist at the surface of an evaporating water droplet. Statistical rate theory has been used to predict the pressure in the vapor to within the experimental uncertainty during each of the experiments. While the qualitative trend of the D2 law is observed to be consistent with the measurements, it underpredicts the measured rate of evaporation by 21%–37%. When the temperature discontinuity is taken into account in the D2 law, the difference between the predicted and measured values is at most 7%. The results suggest that the rate limiting process in the experiments is not diffusion in the gas phase, as is assumed in the D2 law, but is the interface kinetics.