Astrophysics (Index)About

collisional broadening

(pressure broadening)
(line broadening due to nearby particles)

The term collisional broadening refers to line broadening (mechanisms creating width to spectral lines so they are not infinitely narrow) due to the effects of nearby particles which are charged or contain charged sub-particles (the close passes between moving particles that lead to some interaction are termed collisions). The term pressure broadening is also used; such broadening increases with the gas/plasma's pressure which reflects its density and particle momentum, such collisions occurring more frequently. A number of effects result from these interactions, due to various forces and mechanisms, which contribute to the spectral line shape in different ways, producing a combination (convolution) of a Lorentzian profile and a Gaussian profile. An example of such effects is a slight change in the energy-difference between an atom's electron orbitals due to the additional electric force from an electron that is near (either a free electron or one orbiting a nearby atom): the wavelength of a photon emitted or absorbed is thus slightly different.


(lines,spectrum)
Further reading:
https://en.wikipedia.org/wiki/Spectral_line#Pressure_broadening
https://en.wikipedia.org/wiki/Spectral_line_shape#Line_shape_functions
https://sciencedemonstrations.fas.harvard.edu/presentations/collisional-broadening
https://glossary.ametsoc.org/wiki/Collision_broadening

Referenced by pages:
damping profile
line broadening
line shape function
Lorentzian distribution
Stark effect
surface gravity (g)
Voigt profile

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