Astrophysics (index)about


(addition of photons to a beam of EMR)

The term emission is used in the study of radiative transfer and spectroscopy, meaning the addition of photons to a beam of electromagnetic radiation (e.g., light), such as from changes in atoms, and also from scattering. It is the inverse of absorption, the removal of photons to the beam. The concept is used widely in astrophysics, for explaining and modeling stars, for dealing with the effects of the Earth's atmosphere, for explaining and modeling gas clouds, etc. Each type of emission has an absorption analog (though scattering is both emission and absorption), thus the classification of emission processes also is a classification of absorption processes.

Spontaneous emission is the emission of a photon by an atom not from any immediate interaction, such as the emission of a photon when an atom a lower level of atomic excitation (when an electron moves to a lower orbit).

Stimulated emission is the emission of a photon by a similar atom, but specifically when a photon of the same wavelength approaches. Masers and lasers are based on this effect.

Scattering emission includes photons entering the beam through Thomson scattering or Compton scattering.

(physics,EMR,radiative transfer)

Referenced by:
absorption line
active galaxy
advection dominated accretion flow (ADAF)
active galactic nucleus (AGN)
alpha CO (αCO)
anomalous microwave emission (AME)
atmospheric model
atomic excitation
Auger effect
broad emission line region
Be star
black-body radiation
circumstellar disk
cosmic microwave background (CMB)
continuum emission
cooling function
cosmic dust
Cygnus A (3C 405)
diffuse emission
Dwingeloo Obscured Galaxy Survey (DOGS)
DQ Tau
Dickel-Wendker-Bieritz Catalog (DWB)
electron orbital
electron scattering
emission line galaxy (ELG)
emission coefficient (j)
emission line
star formation feedback
GALEX Arecibo SDSS Survey (GASS)
Galactic All-sky Survey (GASS)
greenhouse effect
HI supershell
hyperluminous infrared galaxy (HLIRG)
intensity mapping
line blanketing
luminous infrared galaxy (LIRG)
luminosity (L)
Massive Cluster Survey (MACS)
Mars Exploration Rover (MER)
nitrogen (N)
obscured fraction-luminosity relation
PAH emissions
quantum number
radiative transfer (RT)
redshift (z)
retrograde accretion
radio galaxy (RG)
radiative transfer code (RT code)
equation of radiative transfer (RTE)
radiative transfer model (RTM)
secondary eclipse
Seyfert galaxy
star formation rate (SFR)
spectral band
spectral index (α)
spectral line
spectral signature
spin (ms)
standard model of a flare
state of excitation
stellar flare
synchrotron radiation
Tully-Fisher relation (TFR)
21cm line
transit spectroscopy
transmission spectroscopy
ultraluminous infrared galaxy (ULIRG)