In the alpha decay of atomic nuclei, the mass number. What is alpha decay and beta decay? Beta decay, alpha decay: formulas and reactions. Elements subject to alpha decay

According to modern chemical concepts, an element is a type of atoms with the same nuclear charge, which is reflected in the ordinal number of the element in the table of D.I. Mendeleev. Isotopes may differ in the number of neutrons and, accordingly, in atomic mass, but since the number of positively charged particles - protons - is the same, it is important to understand that we are talking about the same element.

A proton has a mass of 1.0073 amu. (atomic mass units) and charge +1. The unit of electric charge is the charge of an electron. The mass of an electrically neutral neutron is 1.0087 amu. To designate an isotope, it is necessary to indicate its atomic mass, which is the sum of all protons and neutrons, and the charge of the nucleus (the number of protons or, equivalently, the serial number). The atomic mass, also called the nucleon number or nucleon, is usually written to the top left of the element symbol, and the serial number to the bottom left.

A similar notation is used for elementary particles. So, β-rays, which are electrons and have a negligible mass, are assigned a charge of -1 (bottom) and a mass number 0 (top). α-particles are positive doubly charged helium ions, therefore they are denoted by the symbol "He" with a nuclear charge of 2 and a mass number of 4. The relative proton masses p n are taken as 1, and their charges are, respectively, 1 and 0.

Isotopes of elements usually do not have separate names. The only exception is hydrogen: its isotope with a mass number of 1 is protium, 2 is deuterium, and 3 is tritium. The introduction of special names is due to the fact that hydrogen isotopes differ as much as possible from each other in mass.

Isotopes: stable and radioactive

Isotopes are stable and radioactive. The former do not undergo decay, therefore they are preserved in nature in their original form. Examples of stable isotopes are oxygen with an atomic mass of 16, carbon with an atomic mass of 12, and fluorine with an atomic mass of 19. Most natural elements are a mixture of several stable isotopes.

Types of radioactive decay

Radioactive isotopes, natural and artificial, spontaneously decay with the emission of α- or β-particles to form a stable isotope.

They talk about three types of spontaneous nuclear transformations: α-decay, β-decay and γ-decay. During α-decay, the nucleus emits an α-particle consisting of two protons and two neutrons, as a result of which the mass number of the isotope decreases by 4, and the charge of the nucleus decreases by 2. For example, radium decays into radon and a helium ion:

Ra(226, 88)→Rn(222, 86)+He(4, 2).

In the case of β-decay, a neutron in an unstable nucleus turns into a proton, and the nucleus emits a β-particle and an antineutrino. The mass number of the isotope does not change, but the charge of the nucleus increases by 1.

During γ-decay, the excited nucleus emits γ-radiation with a small wavelength. In this case, the energy of the nucleus decreases, but the charge of the nucleus and the mass number remain unchanged.

1. PHYSICS OF THE NUCLEAR 1.4. β-decay

Types and properties of beta decay. Elements of the theory of beta decay. Radioactive families

beta decay nucleus is the process of spontaneous transformation of an unstable nucleus into an isobar nucleus as a result of the emission of an electron (positron) or the capture of an electron. About 900 beta-radioactive nuclei are known. Of these, only 20 are natural, the rest are obtained artificially.
Types and properties of beta decay

There are three types β - decay: electronic β – decay, positron β + -decay and electron capture( e-capture). The first one is the main one.

At electronic β – -decay one of the neutrons of the nucleus turns into a proton with the emission of an electron and an electron antineutrino.

Examples: decay of a free neutron

, T 1/2 = 11.7 min;

tritium decay

, T 1/2 = 12 years old.

At positron β + -decay one of the protons of the nucleus turns into a neutron with the emission of a positively charged electron (positron) and an electron neutrino

. (1.41b)

Example

From a comparison of the half-lives of the ancestors of the families with the geological lifetime of the Earth (4.5 billion years), it can be seen that almost all of thorium-232 is preserved in the Earth's substance, uranium-238 has decayed by about half, uranium-235 - for the most part, neptunium-237 is practically all.

Heavy ion accumulators open up fundamentally new possibilities in studying the properties of exotic nuclei. In particular, they make it possible to accumulate and use for a long time completely ionized atoms - "bare" nuclei. As a result, it becomes possible to study the properties of atomic nuclei that have no electronic environment and in which there is no Coulomb effect of the outer electron shell with the atomic nucleus.

Rice. 3.2 Scheme of e-capture in an isotope (left) and fully ionized atoms and (right)

The decay into a bound state of an atom was first discovered in 1992. The β - decay of a fully ionized atom into bound atomic states was observed. The 163 Dy nucleus on the N-Z diagram of atomic nuclei is marked in black. This means that it is a stable kernel. Indeed, being part of a neutral atom, the 163 Dy nucleus is stable. Its ground state (5/2+) can be populated as a result of e-capture from the ground state (7/2+) of the 163 Ho nucleus. The 163 Ho nucleus surrounded by an electron shell is β - -radioactive and its half-life is ~10 4 years. However, this is true only if we consider the nucleus surrounded by an electron shell. For fully ionized atoms, the picture is fundamentally different. Now the ground state of the 163 Dy nucleus turns out to be higher in energy than the ground state of the 163 Ho nucleus and the possibility opens up for the decay of 163 Dy (Fig. 3.2)

The electron formed as a result of decay can be captured on the vacant K or L-shell of the ion. As a result, decay (3.8) has the form

→ + e - + e (in the bound state).

The energies of β-decays into K and L-shells are (50.3±1) keV and (1.7±1) keV, respectively. To observe the decay into bound states of the K- and L-shells in the ESR storage ring, 10 8 fully ionized nuclei were accumulated at the GSI. During the accumulation time, as a result of β + -decay, nuclei were formed (Fig. 3.3).

Rice. 3.3. Dynamics of ion accumulation: a - current of Dy 66+ ions accumulated in the ESR storage ring during different stages of the experiment, β - intensities of Dy 66+ and Ho 67+ ions, measured by external and internal position-sensitive detectors, respectively

Since the Ho 66+ ions have practically the same M/q ratio as the Dy 66+ ions of the primary beam, they accumulate in the same orbit. The accumulation time was ~30 min. In order to measure the half-life of the Dy 66+ nucleus, the beam accumulated in orbit had to be purified from the admixture of Ho 66+ ions. To clean the beam from ions, an argon gas jet with a density of 6·10 12 atom/cm 2 and a diameter of 3 mm was injected into the chamber, which crossed the accumulated ion beam in the vertical direction. Due to the fact that Ho 66+ ions captured electrons, they dropped out of the equilibrium orbit. The beam was cleaned for approximately 500 s. After that, the gas jet was blocked and the Dy 66+ ions and the newly formed (after the gas jet was switched off) Ho 66+ ions as a result of decay continued to circulate in the ring. The duration of this stage varied from 10 to 85 min. The detection and identification of Ho 66+ was based on the fact that Ho 66+ can be further ionized. To do this, at the last stage, a gas jet was again injected into the storage ring. The last electron was stripped from the 163 Ho 66+ ion, and as a result, the 163 Ho 67+ ion was obtained. A position-sensitive detector was located near the gas jet, which registered the 163 Ho 67+ ions leaving the beam. On fig. 3.4 shows the dependence of the number of 163 Ho nuclei formed as a result of β-decay on the accumulation time. The inset shows the spatial resolution of the position sensitive detector.
Thus, the accumulation of 163 Ho nuclei in the 163 Dy beam proved the possibility of the decay

→ + e - + e (in the bound state).

Rice. 3.4. Ratio of daughter ions 163 Ho 66+ to primary ions 163 Dy 66+ depending on accumulation time. The inset shows the 163 Ho 67+ peak recorded by the internal detector.

By varying the time interval between the cleaning of the beam from the Ho 66+ impurity and the time of detecting Ho 66+ ions newly formed in the impurity beam, one can measure the half-life of the fully ionized Dy 66+ isotope. It turned out to be ~0.1 year.
A similar decay was also found for 187 Re 75+ . The result obtained is extremely important for astrophysics. The fact is that neutral 187 Re atoms have a half-life of 4·10 10 years and are used as radioactive clocks. The half-life of 187 Re 75+ is only 33 ± 2 years. Therefore, appropriate corrections must be made in astrophysical measurements, since in stars, 187 Re is most often in an ionized state.
The study of the properties of fully ionized atoms opens up a new line of research into the exotic properties of nuclei devoid of the Coulomb effect of the outer electron shell.

Alpha and beta radiation are generally called radioactive decays. This is a process that is an emission from the nucleus, occurring at a tremendous speed. As a result, an atom or its isotope can change from one chemical element to another. Alpha and beta decays of nuclei are characteristic of unstable elements. These include all atoms with a charge number greater than 83 and a mass number greater than 209.

Reaction Conditions

Decay, like other radioactive transformations, is natural and artificial. The latter occurs due to the ingress of some foreign particle into the nucleus. How much alpha and beta decay an atom can undergo depends only on how soon a stable state is reached.

Under natural circumstances, alpha and beta minus decays occur.

Under artificial conditions, neutron, positron, proton and other rarer types of decays and transformations of nuclei are present.

These names were given by those who studied radioactive radiation.

Difference between stable and unstable kernel

The ability to decay directly depends on the state of the atom. The so-called "stable" or non-radioactive nucleus is characteristic of non-decaying atoms. In theory, such elements can be observed indefinitely in order to be finally convinced of their stability. This is required in order to separate such nuclei from unstable ones, which have an extremely long half-life.

By mistake, such a "slowed down" atom can be mistaken for a stable one. However, tellurium, and more specifically, its isotope number 128, which has 2.2·10 24 years, can be a striking example. This case is not isolated. Lanthanum-138 has a half-life of 10 11 years. This period is thirty times the age of the existing universe.

The essence of radioactive decay

This process is random. Each decaying radionuclide acquires a rate that is constant for each case. The decay rate cannot change under the influence of external factors. It doesn't matter if a reaction will occur under the influence of a huge gravitational force, at absolute zero, in an electric and magnetic field, during any chemical reaction, and so on. The process can be influenced only by direct impact on the interior of the atomic nucleus, which is practically impossible. The reaction is spontaneous and depends only on the atom in which it proceeds and its internal state.

When referring to radioactive decays, the term "radionuclide" is often used. Those who are not familiar with it should know that this word refers to a group of atoms that have radioactive properties, their own mass number, atomic number and energy status.

Various radionuclides are used in technical, scientific and other areas of human life. For example, in medicine, these elements are used in diagnosing diseases, processing medicines, tools and other items. There are even a number of therapeutic and prognostic radiopreparations.

Equally important is the determination of the isotope. This word refers to a special kind of atoms. They have the same atomic number as an ordinary element, but a different mass number. This difference is caused by the number of neutrons, which do not affect the charge, like protons and electrons, but change their mass. For example, simple hydrogen has as many as 3 of them. This is the only element whose isotopes have been given names: deuterium, tritium (the only radioactive one) and protium. In other cases, the names are given in accordance with the atomic masses and the main element.

Alpha decay

This is a kind of radioactive reaction. It is typical for natural elements from the sixth and seventh periods of the periodic table of chemical elements. Especially for artificial or transuranium elements.

Elements subject to alpha decay

The metals that are characterized by this decay include thorium, uranium and other elements of the sixth and seventh periods from the periodic table of chemical elements, counting from bismuth. Isotopes from among the heavy elements are also subjected to the process.

What happens during a reaction?

In alpha decay, particles are emitted from the nucleus, consisting of 2 protons and a pair of neutrons. The emitted particle itself is the nucleus of a helium atom, with a mass of 4 units and a charge of +2.

As a result, a new element appears, which is located two cells to the left of the original in the periodic table. This arrangement is determined by the fact that the original atom has lost 2 protons and along with it - the initial charge. As a result, the mass of the resulting isotope is reduced by 4 mass units compared to the initial state.

Examples

During this decay, thorium is formed from uranium. From thorium comes radium, from it comes radon, which eventually gives polonium, and finally lead. In this process, isotopes of these elements are formed, and not they themselves. So, it turns out uranium-238, thorium-234, radium-230, radon-236 and so on, up to the appearance of a stable element. The formula for such a reaction is as follows:

Th-234 -> Ra-230 -> Rn-226 -> Po-222 -> Pb-218

The speed of an isolated alpha particle at the moment of emission is from 12,000 to 20,000 km/sec. Being in a vacuum, such a particle would circle the globe in 2 seconds, moving along the equator.

beta decay

The difference between this particle and an electron is in the place of appearance. Beta decay occurs in the nucleus of an atom, not in the electron shell surrounding it. The most common of all existing radioactive transformations. It can be observed in almost all currently existing chemical elements. It follows from this that each element has at least one isotope subject to decay. In most cases, beta decay results in beta-minus decay.

Reaction progress

In this process, an electron is ejected from the nucleus, which has arisen due to the spontaneous transformation of a neutron into an electron and a proton. In this case, due to the greater mass, protons remain in the nucleus, and the electron, called the beta minus particle, leaves the atom. And since there are more protons per unit, the nucleus of the element itself changes upwards and is located to the right of the original one in the periodic table.

Examples

The decay of beta with potassium-40 turns it into an isotope of calcium, which is located on the right. Radioactive calcium-47 becomes scandium-47, which can turn into stable titanium-47. What does this beta decay look like? Formula:

Ca-47 -> Sc-47 -> Ti-47

The escape velocity of a beta particle is 0.9 times the speed of light, which is 270,000 km/sec.

There are not too many beta-active nuclides in nature. There are very few significant ones. An example is potassium-40, which is only 119/10,000 in a natural mixture. Also, among the significant natural beta-minus active radionuclides are the products of alpha and beta decay of uranium and thorium.

The decay of beta has a typical example: thorium-234, which in alpha decay turns into protactinium-234, and then in the same way becomes uranium, but its other isotope number 234. This uranium-234 again due to alpha decay becomes thorium , but a different kind of it. This thorium-230 then becomes radium-226, which turns into radon. And in the same sequence, up to thallium, only with different beta transitions back. This radioactive beta decay ends with the formation of stable lead-206. This transformation has the following formula:

Th-234 -> Pa-234 -> U-234 -> Th-230 -> Ra-226 -> Rn-222 -> At-218 -> Po-214 -> Bi-210 -> Pb-206

Natural and significant beta-active radionuclides are K-40 and elements from thallium to uranium.

Beta plus decay

There is also a beta plus transformation. It is also called positron beta decay. It emits a particle called a positron from the nucleus. The result is the transformation of the original element into the one on the left, which has a lower number.

Example

When electron beta decay occurs, magnesium-23 becomes a stable isotope of sodium. Radioactive europium-150 becomes samarium-150.

The resulting beta decay reaction can create beta+ and beta- emissions. The particle escape velocity in both cases is equal to 0.9 of the speed of light.

Other radioactive decays

In addition to such reactions as alpha decay and beta decay, the formula of which is widely known, there are other processes that are rarer and more characteristic of artificial radionuclides.

neutron decay. A neutral particle of 1 mass unit is emitted. During it, one isotope turns into another with a smaller mass number. An example would be the conversion of lithium-9 to lithium-8, helium-5 to helium-4.

When the stable isotope of iodine-127 is irradiated with gamma rays, it becomes isotope number 126 and acquires radioactivity.

proton decay. It is extremely rare. During it, a proton is emitted, having a charge of +1 and 1 unit of mass. The atomic weight becomes less by one value.

Any radioactive transformation, in particular, radioactive decays, is accompanied by the release of energy in the form of gamma radiation. They call it gamma rays. In some cases, X-rays with lower energy are observed.

It is a stream of gamma quanta. It is electromagnetic radiation, harder than X-ray, which is used in medicine. As a result, gamma quanta appear, or energy flows from the atomic nucleus. X-ray radiation is also electromagnetic, but arises from the electron shells of the atom.

Alpha particle range

Alpha particles with a mass of 4 atomic units and a charge of +2 move in a straight line. Because of this, we can talk about the range of alpha particles.

The value of the run depends on the initial energy and ranges from 3 to 7 (sometimes 13) cm in the air. In a dense medium, it is a hundredth of a millimeter. Such radiation cannot penetrate a sheet of paper and human skin.

Due to its own mass and charge number, the alpha particle has the highest ionizing power and destroys everything in its path. In this regard, alpha radionuclides are the most dangerous for humans and animals when exposed to the body.

Penetrating power of beta particles

Due to the small mass number, which is 1836 times smaller than the proton, the negative charge and size, beta radiation has a weak effect on the substance through which it flies, but, moreover, the flight is longer. Also the path of the particle is not straight. In this regard, they speak of penetrating ability, which depends on the received energy.

The penetrating abilities of beta particles that arose during radioactive decay in air reach 2.3 m, in liquids they are counted in centimeters, and in solids - in fractions of a centimeter. The tissues of the human body transmit radiation to a depth of 1.2 cm. To protect against beta radiation, a simple layer of water up to 10 cm can serve. The flow of particles with a sufficiently high decay energy of 10 MeV is almost completely absorbed by such layers: air - 4 m; aluminum - 2.2 cm; iron - 7.55 mm; lead - 5.2 mm.

Given their small size, beta radiation particles have a low ionizing power compared to alpha particles. However, when ingested, they are much more dangerous than during external exposure.

The highest penetrating performance among all types of radiation currently has neutron and gamma. The range of these radiations in the air sometimes reaches tens and hundreds of meters, but with lower ionizing indices.

Most isotopes of gamma rays do not exceed 1.3 MeV in energy. Rarely, values ​​of 6.7 MeV are reached. In this regard, to protect against such radiation, layers of steel, concrete and lead are used for the attenuation factor.

For example, in order to attenuate cobalt gamma radiation tenfold, a lead shield about 5 cm thick is needed, for a 100-fold attenuation, 9.5 cm is required. Concrete protection will be 33 and 55 cm, and water - 70 and 115 cm.

The ionizing performance of neutrons depends on their energy performance.

In any situation, the best way to protect yourself from radiation is to stay as far away from the source as possible and spend as little time as possible in the area of ​​high radiation.

atomic fission

By atoms is meant spontaneous, or under the influence of neutrons, into two parts, approximately equal in size.

These two parts become radioactive isotopes of elements from the main part of the table of chemical elements. Start from copper to lanthanides.

During the release, a couple of extra neutrons escape and there is an excess of energy in the form of gamma quanta, which is much greater than during radioactive decay. So, in one act of radioactive decay, one gamma quanta appears, and during the act of fission, 8.10 gamma quanta appear. Also, scattered fragments have a large kinetic energy, which turns into thermal indicators.

The released neutrons are capable of provoking the separation of a pair of similar nuclei if they are located nearby and the neutrons hit them.

In this regard, there is a possibility of a branching, accelerating chain reaction of the separation of atomic nuclei and the creation of a large amount of energy.

When such a chain reaction is under control, it can be used for certain purposes. For example, for heating or electricity. Such processes are carried out at nuclear power plants and reactors.

If you lose control over the reaction, then an atomic explosion will occur. Similar is used in nuclear weapons.

Under natural conditions, there is only one element - uranium, which has only one fissile isotope with the number 235. It is a weapon.

In an ordinary uranium nuclear reactor, from uranium-238, under the influence of neutrons, they form a new isotope at number 239, and from it - plutonium, which is artificial and does not occur naturally. In this case, the resulting plutonium-239 is used for weapons purposes. This process of fission of atomic nuclei is the essence of all atomic weapons and energy.

Phenomena such as alpha decay and beta decay, the formula of which is studied in school, are widespread in our time. Thanks to these reactions, there are nuclear power plants and many other industries based on nuclear physics. However, do not forget about the radioactivity of many of these elements. When working with them, special protection and compliance with all precautions are required. Otherwise, it can lead to an irreparable disaster.

beta decay

β-decay, radioactive decay of an atomic nucleus, accompanied by the departure of an electron or positron from the nucleus. This process is due to the spontaneous transformation of one of the nucleons of the nucleus into a nucleon of another kind, namely: the transformation of either a neutron (n) into a proton (p), or a proton into a neutron. In the first case, an electron (e -) flies out of the nucleus - the so-called β - decay occurs. In the second case, a positron (e +) flies out of the nucleus - β + decay occurs. Departing at B.-r. electrons and positrons are collectively referred to as beta particles. Mutual transformations of nucleons are accompanied by the appearance of another particle - a neutrino ( ν ) in the case of β+ decay or antineutrino A, equal to the total number of nucleons in the nucleus, does not change, and the nucleus product is an isobar of the original nucleus, standing next to it to the right in the periodic system of elements. On the contrary, during β + -decay, the number of protons decreases by one, and the number of neutrons increases by one, and an isobar is formed, standing in the neighborhood to the left of the original nucleus. Symbolically, both processes of B.-r. are written in the following form:

where -Z neutrons.

The simplest example of (β - -decay is the transformation of a free neutron into a proton with the emission of an electron and an antineutrino (neutron half-life ≈ 13 min):

A more complex example (β - decay - the decay of a heavy isotope of hydrogen - tritium, consisting of two neutrons (n) and one proton (p):

It is obvious that this process is reduced to β - decay of a bound (nuclear) neutron. In this case, the β-radioactive tritium nucleus turns into the nucleus of the next element in the periodic table - the nucleus of the light helium isotope 3 2 He.

An example of β + decay is the decay of the carbon isotope 11 C according to the following scheme:

The transformation of a proton into a neutron inside the nucleus can also occur as a result of the capture by the proton of one of the electrons from the electron shell of the atom. Most often, electron capture occurs

B.-r. observed in both naturally radioactive and artificially radioactive isotopes. In order for a nucleus to be unstable with respect to one of the types of β-transformation (that is, it could undergo a B.-r.), the sum of the masses of the particles on the left side of the reaction equation must be greater than the sum of the masses of the transformation products. Therefore at B. - river. energy is released. B.'s energy - river. Eβ can be calculated from this mass difference using the relation E = mc2, where With - speed of light in vacuum. In the case of β-decay

where M - masses of neutral atoms. In the case of β+ decay, a neutral atom loses one of the electrons in its shell, the energy of the B.-r. is equal to:

where me- the mass of an electron.

B.'s energy - river. distributed among three particles: an electron (or positron), an antineutrino (or neutrino) and a nucleus; each of the light particles can carry away almost any energy from 0 to E β i.e. their energy spectra are continuous. It is only in K-capture that the neutrino always carries away the same energy.

So, in β - -decay, the mass of the initial atom exceeds the mass of the final atom, and in β + -decay, this excess is at least two electron masses.

B.'s research - river. nuclei has repeatedly presented scientists with unexpected mysteries. After the discovery of radioactivity, B.'s phenomenon - river. has long been considered as an argument in favor of the presence of electrons in atomic nuclei; this assumption turned out to be in clear contradiction with quantum mechanics (see atomic nucleus). Then, the inconstancy of the energy of the electrons emitted during B.-r., even gave rise to disbelief in the law of conservation of energy among some physicists, since. it was known that nuclei in states with a well-defined energy participate in this transformation. The maximum energy of electrons escaping from the nucleus is exactly equal to the difference between the energies of the initial and final nuclei. But in this case, it was not clear where the energy disappears if the emitted electrons carry less energy. The assumption of the German scientist W. Pauli about the existence of a new particle - the neutrino - saved not only the law of conservation of energy, but also another most important law of physics - the law of conservation of angular momentum. Since the spins (i.e., proper moments) of the neutron and proton are equal to 1 / 2, then in order to preserve the spin on the right side of the B.-r. there can only be an odd number of particles with spin 1/2. In particular, in the case of β - decay of a free neutron n → p + e - + ν, only the appearance of an antineutrino excludes the violation of the momentum conservation law.

B.-r. occurs in elements of all parts of the periodic system. The tendency to β-transformation arises due to the presence of an excess of neutrons or protons in a number of isotopes compared to the amount that corresponds to maximum stability. Thus, the tendency to β + decay or K-capture is characteristic of neutron-deficient isotopes, and the tendency to β - decay is characteristic of neutron-rich isotopes. About 1500 β-radioactive isotopes of all elements of the periodic table are known, except for the heaviest ones (Z ≥ 102).

B.'s energy - river. currently known isotopes ranges from

half-lives are in a wide range from 1.3 10 -2 sec(12 N) to Beta decay 2 10 13 years (natural radioactive isotope 180 W).

In the future, B.'s study - river. repeatedly led physicists to the collapse of old ideas. It was established that B. - river. forces of an entirely new nature govern. Despite the long period that has passed since the discovery of B.-r., the nature of the interaction that causes B.-r. has not been fully studied. This interaction was called "weak", because. it is 10 12 times weaker than the nuclear one and 10 9 times weaker than the electromagnetic one (it surpasses only the gravitational interaction; see Weak Interactions). Weak interaction is inherent in all elementary particles (See elementary particles) (except for the photon). Almost half a century passed before physicists discovered that in B.-r. the symmetry between "right" and "left" can be broken. This parity nonconservation has been attributed to the properties of weak interactions.

B.'s studying - river. It also had another important aspect. The lifetime of the nucleus relative to B.-r. and the shape of the spectrum of β-particles depend on the states in which the initial nucleon and the product nucleon are located inside the nucleus. Therefore, the study of B.-r., in addition to information about the nature and properties of weak interactions, significantly expanded the understanding of the structure of atomic nuclei.

B.'s probability - river. depends essentially on how close the states of nucleons in the initial and final nuclei are to each other. If the state of the nucleon does not change (the nucleon seems to remain in the same place), then the probability is maximum and the corresponding transition of the initial state to the final one is called allowed. Such transitions are characteristic of B. - river. light nuclei. Light nuclei contain almost the same number of neutrons and protons. Heavier nuclei have more neutrons than protons. The states of nucleons of different types are essentially different from each other. It complicates B. - river; there are transitions at which B. - river. happens with a low probability. The transition is also hampered by the need to change the spin of the nucleus. Such transitions are called forbidden. The nature of the transition also affects the shape of the energy spectrum of the β-particles.

An experimental study of the energy distribution of electrons emitted by β-radioactive nuclei (beta spectrum) is carried out using a Beta spectrometer. Examples of β-spectra are shown in rice. one and rice. 2 .

Lit.: Alpha, beta and gamma spectroscopy, ed. K. Zigbana, trans. from English, c. 4, M., 1969, Ch. 22-24; Experimental Nuclear Physics, ed. E. Segre, trans. from English, vol. 3, M., 1961.

E. M. Leikin.

Beta spectrum of the neutron. The kinetic is plotted on the x-axis. electron energy E in kev, on the y-axis - the number of electrons N (E) in relative units (vertical lines indicate the limits of measurement errors of electrons with a given energy).

Great Soviet Encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .

See what "Beta decay" is in other dictionaries:

Beta decay, radioactive transformations of atomic nuclei, in the process of rxx, the nuclei emit electrons and antineutrinos (beta decay) or positrons and neutrinos (beta + decay). Departing at B. p. electrons and positrons have a common name. beta particles. At… … Big encyclopedic polytechnic dictionary

Modern Encyclopedia

beta decay- (b decay), a type of radioactivity in which a decaying nucleus emits electrons or positrons. In electronic beta decay (b), a neutron (intranuclear or free) turns into a proton with the emission of an electron and an antineutrino (see ... ... Illustrated Encyclopedic Dictionary

beta decay- (β decay) radioactive transformations of atomic nuclei, during which the nuclei emit electrons and antineutrinos (β decay) or positrons and neutrinos (β+ decay). Departing at B. p. electrons and positrons are collectively called beta particles (β particles) ... Russian encyclopedia of labor protection

- (b decay). spontaneous (spontaneous) transformations of a neutron n into a proton p and a proton into a neutron inside an atom. nuclei (as well as the transformation into a proton of a free neutron), accompanied by the emission of an electron on e or a positron e + and electron antineutrinos ... ... Physical Encyclopedia

Spontaneous transformations of a neutron into a proton and a proton into a neutron inside the atomic nucleus, as well as the transformation of a free neutron into a proton, accompanied by the emission of an electron or positron and a neutrino or antineutrino. double beta decay… … Nuclear power terms

- (see beta) radioactive transformation of the atomic nucleus, in which an electron and an antineutrino or a positron and a neutrino are emitted; in beta decay, the electric charge of the atomic nucleus changes by one, the mass number does not change. New dictionary... ... Dictionary of foreign words of the Russian language

beta decay- beta rays, beta decay, beta particles. The first part is pronounced [beta] ... Dictionary of pronunciation and stress difficulties in modern Russian

Exist., Number of synonyms: 1 decay (28) ASIS Synonym Dictionary. V.N. Trishin. 2013 ... Synonym dictionary

Beta decay, beta decay... Spelling Dictionary

BETA DECAY- (ß decay) radioactive transformation of the atomic nucleus (weak interaction), in which an electron and an antineutrino or a positron and a neutrino are emitted; at B. r. the electric charge of the atomic nucleus changes by one, the mass (see) does not change ... Great Polytechnic Encyclopedia

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• On the problems of radiation and matter in physics. Critical analysis of existing theories: the metaphysical nature of quantum mechanics and the illusory nature of quantum field theory. Alternative - model of flickering particles, Petrov Yu.I. , The book is devoted to the analysis of the problems of unity and opposition of the concepts of "wave" and "particle". In search of a solution to these problems, the mathematical foundations of fundamental ... Category: