Gamma particles are gamma rays which are electromagnetic radiations emitted from a source during the process of radioactive decay. They are represented by the symbol “γ” and have the shortest wavelength, with frequencies above 30 exahertz (30 x 1018 Hz).
Gamma particles have an energy range from a few kilo-electron volts (keV) to 8 mega-electron volts (MeV). However, high-energy gamma particles are also observed under the range of 100-1000 tera-electron volts (TeV). Gamma particles have an energy spectrum that can be used to identify decaying radionuclides by using the gamma spectroscopy technique.
In 1900, gamma particles were discovered by a French chemist, named Paul Villard, during his work on radium. Later in 1903, Ernest Rutherford named these particles “gamma rays” on the basis of his experiment which showed gamma particles have strong penetration power compared to alpha and beta particles.
Properties of Gamma particles
Some important properties of gamma rays are:
Gamma particles are uncharged particles and are unaffected by electric or magnetic fields. They are electromagnetic rays analogous to X-rays and have the shortest wavelengths.
Gamma rays travel at extremely high speeds, nearly equal to the speed of light.
They also cause ionization of the gases but have less ionization power than alpha particles and beta particles.
Gamma rays have very little effect on the zinc sulfide and photographic plates. That’s why they produce very little luminescence.
- Penetration power
Due to their very short wavelength, gamma particles have a very high penetrating power. It is almost 10-100 times greater than beta particles. They can be stopped by several centimeters (thickness) of concrete.
Sources of Gamma (γ) particles
The major sources of gamma rays are:
- Gamma decay
- Particle physics
- Terrestrial gamma-ray flash
- Cosmic rays
- Solar flares
- Pulsars and magnetars
- Quasars and galaxies
- Gamma-ray bursts
Gamma decay is a process in which radioactive nuclei decay and produce gamma particles. It is the best source of gamma radiations and usually occurs after the production of alpha and beta particles. When alpha and beta decay occurs in a heavy nucleus, this results in a daughter nucleus which undergoes gamma decay and produces gamma particles.
Gamma rays are emitted from the radioactive daughter nucleus in 10-12 seconds and they follow the pathway of nuclear reactions such as fission or fusion reactions and neutron capture. When high-energy gamma rays are bombarded on materials, the atoms in an excited state emit secondary particles called secondary gamma rays. For example, the formation of fluorescent gamma rays is through secondary gamma rays production.
Particle physics is another important source of gamma rays. When neutral system decay through electromagnetic interaction, they produce gamma rays. For example, electron-positron annihilation results in two gamma-ray photons. However, at rest, the resulting two gamma rays have an energy of 511 keV and a frequency of 1.24 x 1020 Hz. Similarly, neutral pions decay into two gamma-ray photons. Hadrons and bosons also decay and produce gamma rays.
Terrestrial gamma-ray flash
Thunderstorms also produce gamma rays for a short period of time, for which they are generally called terrestrial gamma-ray flashes. These gamma rays are produced by the high-intensity accelerating electrons that produce gamma-ray by breaking radiations during collisions with atoms in the air. The gamma rays produced by this process have an energy of 100 MeV.
Cosmic rays are another source of gamma rays that are produced when cosmic rays collide with the matter. These gamma rays have an energy of 511 keV. On the other hand, deceleration radiations are made with different energies, or sometimes more, when cosmic ray electrons collide with atoms that have a high atomic number.
Solar flares naturally produced gamma rays. They are the intense eruptions of electromagnetic radiation in the sun and have high energy. The high-energy solar flares emit gamma rays with other particles in the solar system.
Pulsars and magnetars
Pulsars are the stars in the sky and emit electromagnetic radiation especially gamma rays. Similarly, other sources of gamma rays are quasars. However, pulsars are neutron-base stars that produce a specific beam of radiation which have less energy.
Pulsars have long-lived magnetic fields that produce charged particles at high speed. When these charged particles strike the gas or dust particles, they produce gamma rays. This is a similar mechanism that is used in the production of high-energy photons in megavoltage radiation therapy.
Inverse Compton scattering is another process that enhances the speed and energy of photons. During the process, electrons transfer their energy to the low-energy photons which converts them into high-energy photons. These high-energy photons are another mechanism to produce high-energy gamma rays.
Pulsars with very high magnetic fields are called magnetars. They also produce astronomical soft gamma repeaters which are also the sources of gamma rays.
Quasars and galaxies
Quasars and active galaxies have sources of gamma rays production which are similar to particle accelerators. Active galaxies have supermassive black holes which provide power sources and destroy the stars. This results in the production of charged particles in the form of a beam. When this beam interacts or strikes with the dust or gas particles and lower energy photons, they produce gamma rays.
Gamma-ray bursts are a very rare source of gamma rays and occur in galaxies. They are very intense explosions that produce gamma rays. They can last from a few seconds to several hours. On the basis of time, they have two types: short-duration bursts (short-lived) and long-duration bursts (long-lived) of gamma rays.
Gamma spectroscopy is a technique in which the energy transition of the atomic nucleus is studied by the absorption or emission of gamma rays. Generally, in optical spectroscopy, the absorption of gamma rays by the atomic nuclei can be seen as peaks in a resonance, when the energy of gamma rays and energy transitions in the atomic nuclei are the same.
However, in the case of gamma rays, such type of resonances can be seen by using the Mossbauer spectroscopy technique. In the Mossbauer effect, resonance absorption for nuclear gamma absorption can be gained by immobilizing atomic nuclei in a crystal. To prevent gamma energy from being lost to the kinetic energy of recoiling nuclei at either the emitting or absorbing end of a gamma transition, nuclei must be immobilized at both ends of a gamma resonance interaction.
Health effects of Gamma particles
The effects of gamma radiation on the human body are:
- Gamma rays are more penetrating than alpha and beta rays. Therefore, they can cause damage at the cellular level.
- Low-level health effects of gamma rays are stochastic health effects which are cancer induction and genetic damage.
- Whereas high-level health risks of gamma rays are deterministic effects that are severe/acute tissue damage.
- Gamma rays can also affect the DNA of the human body and absorption of gamma rays can break it.
- They can also cause a syndrome of nausea, hair loss, and hemorrhaging.
- A higher dose of gamma rays 5 Sv (unit) can cause death.
Applications of Gamma particles
The important applications and uses of gamma rays are:
- Gamma rays are used to change the properties of gemstones. For example, they are used to convert white topaz into blue topaz.
- Sources of gamma radiation are used in industrial sensors to measure the level, density, and thickness of the substances. They are used in industries such as paper, soap, detergent, mining, refining, etc.
- Gamma rays detectors are used in Container Security Initiative (CSI) machines. They can detect and scan 30 containers in one hour.
- Gamma rays are used to kill microorganisms like bacteria. For example, the sterilization of medical equipment with gamma rays.
- They are also used to remove decay-causing living organisms from fruits and vegetables. They also prevent fruit from sprouting and maintain them as fresh.
- These rays are also used in the field of medicine. They are used to treat cancer in the human body by a technique called gamma knife surgery. Gamma rays strike at the site of the growth of cancerous cells and kill them.
- In nuclear medicine, gamma particles are used for diagnostic purposes. For example, radio-labeled sugar is used in a PET scan to highlight cancer. This radio-labeled sugar emits positrons that are destroyed by the high-energy electrons and produce gamma rays that diagnose cancer.
- Gamma rays are also used to obtain high energy, like X-rays. For this purpose, gamma-ray emitters are used like technetium-99m.
What can gamma rays pass through?
Gamma rays have less ionization power and a high penetrating power. Therefore, they can pass through paper, lead, and aluminum sheets but can be stopped by a thick wall of concrete.
How are gamma rays produced?
Gamma rays can be produced by gamma decay in which a heavy nucleus decays and emits gamma particles.
Are gamma rays harmful?
Yes, gamma particles are very dangerous to health, because they have higher penetration power and can damage at the cellular level.
What can gamma rays be used for?
Gamma rays are used for industrial purposes and in the medical field. Industries use gamma rays for the measurement and detection of paper thickness, etc. while medical fields use gamma rays for the diagnosis and treatment of cancer.
Where do gamma rays come from?
Gamma rays come from radioactive material. When radioactive materials decay, they emit gamma particles.
What produces gamma rays?
Gamma particles are produced by the whole universe, such as star flares, pulsars, quasars, galaxies, radioactive elements, etc. However, in the laboratory, they are produced by their common sources.
What are alpha beta and gamma particles?
Alpha, beta, and gamma particles are radiations emitted by the decay of a heavy nucleus. Alpha and beta particles have high ionization power and less penetration power than gamma particles.
- Ionizing radiation (Arpansa.gov.au)