Bremsstrahlung Radiation
Bremsstrahlung radiation, often referred to as "braking radiation," is a type of electromagnetic radiation generated when a charged particle, typically an electron, experiences a rapid deceleration, usually due to interactions with electric fields, such as atomic nuclei. During this deceleration, the electron loses kinetic energy, which is emitted in the form of a photon, a fundamental particle of electromagnetic radiation. This process is significant in the production of x-rays, which can occur through two primary mechanisms: K-shell emissions and bremsstrahlung.
Bremsstrahlung is categorized into two forms: electron-nucleus and electron-electron interactions, with the former being more prevalent. Importantly, the radiation from free electrons, which are not bound to atoms, leads to a continuous spectrum often called free-free radiation. The study of bremsstrahlung is crucial across various fields of physics, particularly in astrophysics, where it informs our understanding of cosmic rays and other celestial phenomena. As research continues, advancements in technology, such as the NuSTAR space observatory, enhance our ability to detect and analyze bremsstrahlung, contributing to our broader understanding of the universe.
Bremsstrahlung Radiation
FIELDS OF STUDY: Astrophysics
ABSTRACT: Bremsstrahlung radiation is electromagnetic radiation that is produced when a highly charged particle, such as an electron, hits the nucleus of an atom or another electron and emits a photon. The bremsstrahlung process often produces x-rays. Bremsstrahlung occurs in ionized gas clouds and in cosmic rays.
Braking Electrons
Bremsstrahlung radiation is a type of electromagnetic radiation that is produced when a charged particle, most often an electron, abruptly slows down because it hits an electric field, such as the nucleus of an atom. When the electron slows, its kinetic energy is transformed, and it emits a photon. Photons are the elementary particles that make up all forms of electromagnetic radiation. The process that creates bremsstrahlung radiation is called the bremsstrahlung process. Bremsstrahlung is one method of creating x-rays.
German physicist Wilhelm C. Röntgen (1845–1923) discovered x-rays in 1895. Four years later, another German physicist, Arnold Sommerfeld (1868–1951), discovered that x-rays come in two different types. The first type, known as characteristic x-rays, produces radiation at discrete frequencies, while the second type produces a continuous spectrum. Sommerfeld suggested that the second type be named bremsstrahlung, or "braking radiation," in reference to the sudden electron deceleration that causes it.
The first calculations for bremsstrahlung were devised in the 1930s. Decades later, in the 1960s, the first elementary measurements of bremsstrahlung were made. Scientists continue to study bremsstrahlung in hopes of learning more about cosmic rays, supernovas, and other phenomena in the universe. Such research is fostered by new technological advances such as the NuSTAR space observatory, which is able to detect x-rays.
Attributes of Bremsstrahlung
Radiation is the emission of energy through electromagnetic waves. X-rays are a type of radiation that is made up of photons. They can be produced by bombarding metal x-ray tubes with high-energy electrons. When the energetic electrons hit the metal, they can produce x-rays in two main ways. Electrons that are associated with atoms produce x-rays through K-shell emissions, which occur when lower-energy electrons are knocked out of their orbits and then replaced by higher-energy electrons. The energy lost by the displaced electrons is emitted in the form of an x-ray photon.
Other electrons produce x-rays through bremsstrahlung. Electrons involved in bremsstrahlung deflect off the nucleus of an atom or off another electron. When the electrons are deflected, they lose some of their kinetic energy. As in K-shell emission, the energy lost is emitted as a photon. The type of photon emitted is determined by the change in kinetic energy. Electrons with more kinetic energy will release an x-ray photon. A less energetic electron may produce a photon with a longer wavelength.
Types of Bremsstrahlung
Bremsstrahlung happens in two forms: electron-nucleus or electron-electron. In electron-nucleus bremsstrahlung, the free electron collides with the nucleus of another atom. In electron-electron bremsstrahlung, the free electron collides with another electron. Electron-nucleus bremsstrahlung is the more common of the two types.
Some electrons that are involved in bremsstrahlung are not bound to an atom or an ion before or after the bremsstrahlung. Therefore, they are called "free" electrons. The free electrons create a type of continuous radiation. Radiation from these free electrons is sometimes called free-free radiation. Free-free radiation can come from hydrogen clouds, which can form around the exteriors of active comets.
Studying Bremsstrahlung
Bremsstrahlung is an important concept in all areas of physics, including atomic, nuclear, solid-state, and elementary particle physics. However, it has been of particular importance to astrophysics, where it is used in experimental research. Astrophysicists have learned that bremsstrahlung affects which cosmic-ray particles reach Earth.
Electrons are more likely than other types of particles to be involved in bremsstrahlung because their smaller mass makes them easier to deflect in a collision. It is this deflection that causes the loss of kinetic energy in the form of a photon. Heavier particles, such as muons, have greater momentum due to their greater mass, so they lose less energy than electrons when they collide with other particles. Because of this, they are less likely to be involved in bremsstrahlung and can travel more deeply into a material. This is why muons that enter Earth’s atmosphere in cosmic rays often travel all the way to Earth, while many electrons in cosmic rays do not.
PRINCIPAL TERMS
- continuous spectrum: electromagnetic radiation that is emitted at all frequencies and wavelengths within a given range, with no apparent gaps.
- electron: a negatively charged subatomic particle.
- free-free radiation: radiation produced from electrons that are not associated with atoms or ions before or after bremsstrahlung.
- x-rays: electromagnetic radiation made of up of photons that can be produced through bremsstrahlung.
Bibliography
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