Astrophysics (index)


(addition of photons to a beam of EMR)

The term Emission is used in the study of Radiative Transfer (RT) and Spectroscopy to mean the addition of photons to a beam of Electromagnetic Radiation (EMR) (e.g., light), from changes in atoms, and 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 Absorption has an Emission inverse, or if it is Scattering, is both absorption and emission, thus the classification of absorption processes also is a possible classification of emission processes.

Spontaneous Emission is the emission of a photon by an atom not from any immediate interaction, e.g., the emission of a photon when an atom a lower level of Atomic Excitation, e.g., 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. This is the effect used by Masers and Lasers.

Emission also includes photons which enter the beam through scattering, e.g., Thomson Scattering or Compton Scattering.


Referenced by:
Absorption Line
Active Galaxy
Active Galactic Nucleus (AGN)
Alpha CO (αCO)
Atmospheric Model
Atomic Excitation
Be Star
Black-Body Radiation
Cold Gas
Compton Scattering
Continuum Emission
DQ Tau
Electron Orbital
Emission Line Galaxy (ELG)
Emission Coefficient (j)
Emission Line
Europa Clipper
GALEX Arecibo SDSS Survey (GASS)
Galactic All-Sky Survey (GASS)
HI Supershell
Luminosity (L)
Nitrogen (N)
PAH Emissions
Radiative Transfer (RT)
Radiative Transfer Code (RT Code)
Equation of Radiative Transfer (RTE)
Radiative Transfer Model (RTM)
Star Formation Rate (SFR)
Spectral Band
Spectral Line
State of Excitation
Stellar Flare
Tully-Fisher Relation (TFR)
21cm Line
Transmission Spectroscopy