Velocity and angular distributions of molecules emitted from a liquid surface

Evaporation from the surface of a liquid is considered from the viewpoints of the kinetic theory of gases, capillary-wave theory, and statistical reaction-rate theory. The velocity vectors of molecules emitted from a planar surface are concentrated around the normal to the surface and their velocity distribution is non-Maxwellian. The abnormal velocity distribution and high mean kinetic energy of molecules emitted from a liquid surface provide a mechanism for coupling of heat and matter fluxes in the gas within a few mean paths of the surface.