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## Bremsstrahlung
Bremsstrahlung may also be referred to as free-free radiation. This refers to the radiation that arises as a result of a charged particle that is free both before and after the deflection (acceleration) that causes the emission. Strictly speaking, bremsstrahlung refers to any radiation due to the acceleration of a charged particle, which includes synchrotron radiation; however, it is frequently used (even when not speaking German) in the more narrow sense of radiation from electrons stopping in matter. The word
## Additional recommended knowledge
## Outer"Outer bremsstrahlung" is the term applied in cases where the energy loss by radiation greatly exceeds that by ionization as a stopping mechanism in matter. This is seen clearly for electrons with energies above 50 keV. ## Inner"Inner bremsstrahlung" is the term applied to the less frequent case of radiation emission during beta decay, resulting in the emission of a photon of energy less than or equal to the maximum energy available in the nuclear transition. Inner bremsstrahlung is caused by the abrupt change in the electric field in the region of the nucleus of the atom undergoing decay, in a manner similar to that which causes outer bremsstrahlung. In electron and positron emission the photon's energy comes from the electron/neutron pair, with the spectrum of the bremsstrahlung decreasing continuously with increasing energy of the beta particle. In electron capture the energy comes at the expense of the neutrino, and the spectrum is greatest at about one third of the normal neutrino energy, reaching zero at zero energy and at normal neutrino energy. Beta particle emitting substances sometimes exhibit a weak radiation with continuous spectrum that is due to both outer and inner bremsstrahlung, or to one of them alone. ## Secondary radiationBremsstrahlung is a type of "secondary radiation", in that it is produced as a result of stopping (or slowing) the primary radiation (beta particles). In some cases, ## The case where acceleration is parallel to velocityIf a particle of charge - ,
- where and θ is the angle from .
Integration by parts then gives the total power emitted as - ,
- where is the Lorentz factor.
Note that, since , for a given energy ## From a plasma
In a plasma the free electrons are constantly producing Bremsstrahlung in collisions with the ions. The power spectral density (power per angular frequency interval per volume, integrated over all solid angle) of the Bremsstrahlung radiated, is calculated to be
The special function
( For the case
Note the appearance of the fine structure constant α due to the quantum nature of λ
This formula agrees with the theoretical estimate if we set K=3.17; the value K=3 is suggested by Ichimaru. For very high temperatures there are relativistic corrections to this formula, that is, additional terms of order ## In astrophysicsThe dominant luminous component in a cluster of galaxies is the 10 where speed, The bulk emission from this gas is thermal Bremsstrahlung. The power emitted per cubic centimeter per second can be written in the compact form with cgs units [erg cm below which no photons are created because the energy supplied by acceleration of the electron by the positively charged nucleus is less than the minimum energy required for creation of a photon. This process is also known as Bremsstrahlung cooling since the plasma is optically thin to photons at these energies and the energy radiated is emitted freely into the universe. This radiation is in the energy range of X-rays and can be easily observed with space-based telescopes such as Chandra X-ray Observatory, XMM-Newton, ROSAT, ASCA, EXOSAT, Astro-E2, and future missions like Con-X and NeXT[3].
## References**^***Introduction to Electrodynamics*, 3rd edition, David J. Griffiths, pages 463–464.**^***Basic Principles of Plasmas Physics: A Statistical Approach,*S. Ichimaru, p. 228.**^**NRL Plasma Formulary, 2006 Revision, p. 58.
## See also- Synchrotron light
- Cyclotron radiation
- Nuclear fusion: Bremsstrahlung losses
- X-rays: History
Categories: Atomic physics | Plasma physics | Scattering |
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This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Bremsstrahlung". A list of authors is available in Wikipedia. |