Astrophysics (Index)About

Doppler broadening

(thermal broadening, thermal Doppler broadening)
(broadening of spectral lines due to movement of the source photons)

The term Doppler broadening refers to line broadening (mechanisms creating width to spectral lines so they are not infinitely narrow) stemming from the motion of the molecules, which results in Doppler shifts in the wavelengths emitted. This can be thermal broadening (thermal Doppler broadening), i.e., from motion associated with the temperature of the material, or may be due to turbulence, or due to an ordered (non-random) motion. The shape stemming from thermal broadening is a Gaussian profile and I think that sufficiently-random turbulence can produce the same profile, making it harder to work out temperature from the line profile. Any non-random motion produces its own specific shape, for example, two peaks if from a shell-shape structure that is expanding such that some of the gas is moving toward us and other moving away from us.


(lines,spectrum,EMR,Doppler)
Further reading:
http://en.wikipedia.org/wiki/Doppler_broadening
https://en.wikipedia.org/wiki/Spectral_line#Thermal_Doppler_broadening
https://en.wikipedia.org/wiki/Spectral_line_shape#Line_shape_functions

Referenced by pages:
active galactic nucleus (AGN)
broad emission line region
broad-line region (BLR)
damping profile
line broadening
line shape function
Voigt profile
Wilson-Bappu effect
Wolf-Rayet star

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