The Knudsen layer, also known as evaporation layer, is the thin layer of vapor near a liquid or solid. It is named after Danish physicist Martin Knudsen (1871–1949).
Definition.
At the interface of a vapor and a liquid/solid, the gas interaction with the liquid/solid dominates the gas behavior, and the gas is, very locally, not in equilibrium. This region, several mean free path lengths thick, is called the Knudsen layer.
Knudsen layer thickness.
The Knudsen layer thickness can be approximated by formula_1, given by
 formula_2,
where formula_3 is the Boltzmann constant, formula_4 is the temperature, formula_5 is the molecular diameter and formula_6 is the pressure.
Applications.
One of the applications of Knudsen layer is in the coma of comets. It has been used specially in the coma chemistry model (ComChem model).
References.
 ;templatestyles src="Reflist/styles.css" / ;