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arXiv · 2103.07285

On the velocity distribution function of spontaneously evaporating atoms

Sergiu Busuioc·Livio Gibelli·Duncan A. Lockerby·James E. Sprittles
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Abstract

Numerical solutions of the Enskog-Vlasov (EV) equation are used to determine the velocity distribution function of atoms spontaneously evaporating into near-vacuum conditions. It is found that an accurate approximation is provided by a half-Maxwellian including a drift velocity combined with different characteristic temperatures for the velocity components normal and parallel to the liquid-vapor interface. The drift velocity and the temperature anisotropy reduce as the liquid bulk temperature decreases but persist for relatively low temperatures corresponding to a vapor behaviour which is only slightly non-ideal. Deviations from the undrifted isotropic half-Maxwellian are shown to be consequences of collisions in the liquid-vapor interface which preferentially backscatter atoms with lower normal-velocity component.

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Sergiu Busuioc, Livio Gibelli, Duncan A. Lockerby, James E. Sprittles. 2021-03-12. On the velocity distribution function of spontaneously evaporating atoms. https://doi.org/10.1103/physrevfluids.5.103401

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