The Knudsen layer, also known as evaporation layer, is the thin layer between liquid and vapour. It is named after Danish physicist Martin Knudsen (1871–1949).

Contents 1 Definition 2 Knudsen layer thickness 3 Applications 4 References

[edit] Definition

On molecular level, the state of matter can be hard to define. From kinetic theory, it can be derived that if liquid is in contact with vapour, there is a small layer where the phase is between liquid and vapour. This region, several mean free path lengths thick, is called the Knudsen layer.^[1]

[edit] Knudsen layer thickness

The knudsen layer thickness can be approximated by l_c, given by^[2]

,

where k is Boltzmann's constant, T_s is the temperature, d is the molecular diameter and p_s is the pressure.

[edit] 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). (Huebner et.al 1987)

[edit] References

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