Emission coefficient

Emission coefficient is a coefficient in the power output per unit time of an electromagnetic source, a calculated value in physics. It is also used as a measure of environmental emissions (by mass) per MWh of electricity generated, see: Emission factor.

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Scattering of light

In Thomson scattering a charged particle emits radiation under incident light. The particle may be an ordinary atomic electron, so emission coefficients have practical applications.

If X dV dΩ dλ is the energy scattered by a volume element dV into solid angle dΩ between wavelengths λ and λ+dλ per unit time then the Emission coefficient is X.

The values of X in Thomson scattering can be predicted from incident flux, the density of the charged particles and their Thomson differential cross section (area/solid angle).

Spontaneous Emission

A warm body emitting photons has a monochromatic emission coefficient relating its temperature and total power radiation, this is sometimes called the second "Einstein coefficient", and can be deduced from quantum mechanical theory.

See also

• The Diode equation includes the emission coefficient
• Plasma physics.
• An emission coefficient is also given for ballistic secondary electron emission.
• Luminous coefficient