Kavli Affiliate: David T. Limmer
| First 5 Authors: Kritanjan Polley, Kevin R. Wilson, David T. Limmer, ,
| Summary:
We investigate the evaporation of trace amounts of helium solvated in liquid
water using molecular dynamics simulations and theory. Consistent with
experimental observations, we find a super-Maxwellian distribution of kinetic
energies of evaporated helium. This excess of kinetic energy over typical
thermal expectations is explained by an effective continuum theory of
evaporation based on a Fokker-Planck equation, parameterized molecularly by a
potential of mean force and position-dependent friction. Using this
description, we find that helium evaporation is strongly influenced by the
friction near the interface, which is anomalously small near the Gibbs dividing
surface due to the ability of the liquid-vapor interface to deform around the
gas particle. Our reduced description provides a mechanistic interpretation of
trace gas evaporation as the motion of an underdamped particle in a potential
subject to a viscous environment that varies rapidly across the air-water
interface. From it we predict the temperature dependence of the excess kinetic
energy of evaporation, which is yet to be measured.
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