The nuclei of some atoms are characterized by instability, which manifests itself in their ability to transform (spontaneous decay), accompanied by the emission of radiation (ionizing radiation). The most common type of decay of nuclei is beta radiation.
Radiation refers to various microparticles and physical fields that have the ability to ionize substances. It exists until its own absorption by any substance. Sources of radiation (technical nuclear installations or simply radioactive substances) are able, unlike radiation itself, to exist for a very long time. Natural radiation is constantly present in our lives. Ionizing radiation existed even before the birth of the first forms of life on Earth.
Beta radiation is a continuous stream of positrons or electrons that is emitted during beta-radioactive atomic decay. Such decay is not characteristic of all atoms, but only of certain substances. Electrons (or positrons) are formed in nuclei during the conversion of neutrons into protons or vice versa. The resulting stable particles, which do not have a rest mass and charge, are called neutrinos and antineutrinos.
In electronic decay, a nucleus is formed, the number of protons in which increases by one, compared with the number before decay. With positron decay, the nuclear charge per unit decreases. In both cases, the mass number does not change.
The emitted electrons (or positrons) have different energies, ranging from zero to the maximum limit energy Em (equal to several megaelectron-volts).
Beta radiation has a continuous spectrum of energy. The nuclear energy levels are discrete. This means that with each subsequent decay, new energy will be released. Such a continuity of the emission spectra is explained by the fact that during decay, excess atomic energy can be distributed between the emitted particles in different ways. Therefore, the spectrum of neutrinos that are emitted during decay is also characterized by continuity.
Beta radiation is measured by beta spectrometers, special beta counters and ionization chambers
Radioactive isotopes, which during decay are accompanied by radiation of this type, are called beta emitters. These include isotopes of sulfur (S35), phosphorus (P32), calcium (Ca45), etc. If decay is not accompanied by gamma radiation, then it is called pure beta radiation.
Many emitters (P32, C14, Ca45, S35, etc.) are also used in radioisotope diagnostics and are used for experimental purposes.
Passing through matter, beta rays (beta radiation) interact with the nuclei of its atoms and electrons, spending all their energy on it and almost completely stopping their movement. The path that a beta particle travels through is called a path. It is expressed in grams per square centimeter (indicated as g / cm2).
Beta radiation is able to penetrate into the tissues of a living organism to a depth of 2 centimeters. A plexiglass screen of appropriate thickness can protect against such radiation.
Beta rays are a type of ionizing radiation. When passing through a substance, the rays lose their energy, causing ionization. The absorption of this energy by the medium can cause a number of secondary processes in the material that has been irradiated. For example, this can manifest itself in luminescence, radiation-chemical reactions, changes in the crystal structure of substances, etc. Just like other types of radiation, beta rays have a radiobiological effect.
The use of beta radiation in medicine is based on its penetrating properties in tissue. Rays are used in superficial, intracavitary and interstitial radiation therapy.