What is a beta particle?
By Fajans' law, if an atom emits a beta particle, its electrical charge increases by a positive unit and the number of atomic mass does not vary. This is because the mass or mass number only represents the number of protons and neutrons, which in this case the total number is not affected, since a neutron "loses" an electron, but becomes a proton, that is , a neutron becomes a proton and therefore the total number of atomic mass (protons plus neutrons) does not vary.
The interaction of beta particles with matter generally has a range of action ten times greater and an ionizing power equal to one tenth compared to the interaction of alpha particles. They can be completely blocked with a few millimeters of aluminum.
With regard to health, beta particles are moderately penetrating into living tissue and can cause spontaneous mutations in the DNA.
Beta sources can be used in radiation therapy to kill cancer cells.
Definition of beta radiation
This radiation takes the form of beta (β) particles, which are high-energy particles, expelled from an atomic nucleus in a process known as beta decay. There are two forms of beta decay, β - and β +, which respectively emit an electron or a positron.
Due to the presence of the neutrino, the atom and the beta particle do not normally recede in opposite directions. This observation seemed to violate the principle of conservation of energy and momentum, but as such it did not seem likely, Wolfgang Pauli postulated the existence of a third neutral particle whose name, neutrino, was coined by the Italian Edoardo. Amaldi, a close collaborator of Enrico Fermi, who in turn developed a theory of beta decay that can still be considered valid within an optimal approximation level. This decline is mediated by weak nuclear force.
Properties of beta particles
The energy of the beta particles is continuously distributed from zero to a certain maximum energy, depending on the decaying isotope; this maximum energy is in the range of 2.5 keV (for rhenium-187) to tens of MeV (for short-lived cores away from the beta stability line).
Beta rays deviate from the rectilinear direction under the influence of electric and magnetic fields. The speed of the particles in beta rays is close to the speed of light. Beta rays are capable of ionizing gases, causing chemical reactions, luminescence, acting on photographic plates; as he did during the experiments carried out by Antoine Henri Becquerel that led him to the discovery of radioactivity.
Beta β decay is a type of radioactive decay caused by a weak interaction and the change of nuclear charge in one without changing the mass number. In this decay, the nucleus emits a beta particle (which can be an electron or positron), as well as a neutral particle with a spin of whole medium (electronic antineutrino or electronic neutrino).
Traditionally, beta decay includes decay of two types:
- the nucleus (or neutron) emits an electron and an antineutrino - "beta minus disintegration" (β -).
- The nucleus emits a positron and a neutrino - "beta plus decay" (β +).
In electronic decay, an antineutrino arises, in the decay of positrons - neutrino. This is due to the fundamental law of conservation of the charge of leptons.
In addition to the β - and β + decays, beta decays also include electron capture, in which the nucleus of the atom captures an electron from its electron shell and emits an electron neutrino. Neutrinos (antineutrinos), unlike electrons and positrons, interact extremely weakly with matter and eliminate some of the available decomposition energy.
Uses of beta particles
In the field of nuclear energy, beta particles have medical applications. These β particles can be used to treat health problems such as cancer of the eyes and bones and are also used as markers. Strontium 90 is the most used material to produce beta particles.
Beta particles are also used in quality control to test the thickness of an element, such as paper, that comes through a roller system. Some of the beta radiation is absorbed as it passes through the product. If the product is too thick or thin, a correspondingly different amount of radiation will be absorbed. A computer program that monitors the quality of the manufactured paper will move the rollers to change the thickness of the final product.
A lighting device called betalight contains tritium and a phosphorus. When the tritium disintegrates, it emits beta particles; these hit the match, causing the match to emit photons, like the cathode ray tube of a television. The lighting does not require external energy and will continue as long as the tritium exists (and the matches do not change chemically); The amount of light produced will decrease to half of its original value in 12.32 years, the half-life of the tritium.
- Radioactivity and alpha, beta, gamma and Xrays (en)
- Rays and Particles University of Virginia Lecture Notes (en)
- Basic Nuclear Science Information at the Lawrence Berkeley National Laboratory (en)
Last review: January 31, 2020