The Atom Velocity Distribution Function in the Process of Liquid Evaporation

Analytical expressions determining the velocity distribution function of evaporating particles were obtained for evaporation into a vacuum. The formulas are compared with numerical simulation results; the coincidence can be treated as sufficiently good. The particle distribution function over the longitudinal, i.e., directed from evaporation surface, velocity turns out to be significantly non-Maxwellian. The distribution function over the transverse projections of the velocity is Maxwellian but with a distribution modulus different from the evaporating liquid temperature $T$. The mean energy of a particle escaping from the surface is $2kT$.