() αshè line

The process by which a shèxìng nucleus decays into another nucleus is called α decay, and the α particle is a high-speed helium nucleus with a +2 charge, which passes through the substance, mainly by colliding with electrons. The ability of α particles to penetrate in matter is often expressed in terms of shè process, which refers to the maximum distance that the incoming particle travels in the direction of the incoming shè. Because the mass of the α particle is much larger than that of the electron, after it collides with the electron, it hardly changes the direction of motion, and the probability of being scattered by the nucleus is very small, so the path of the α particle in matter is basically a straight line, and its path length is almost equal to the shè process.

Since solid matter is much denser than air, α particles have a very short shè in solids. For example, a α particle with an energy of 5 MeV has a shè of 23 μm in aluminum.

When α particle passes through the substance, the electrons outside the nucleus of the atom of the substance are subjected to the Coulombic action of the α particle and gain energy. If the energy obtained by the window can overcome the bondage of the nucleus, it becomes an electron, and the atom is ionized. If the energy gained by the electrons is not enough to produce ionization, the atom is excited.

When α particles pass through the substance, it is also possible to interact with the nucleus of the atom, which is called Rutherford.

βshè line

The βshè line is a fast flow of electrons with a small mass and high velocity, so its interaction with the atoms of matter is very different from that of α particles. Table xiàn has a small ionization energy loss rate, so it has strong penetrating ability, and can produce tough radiations in the nuclear Coulomb field, which is easy to be dispersed by nuclei and electrons to form multiple scattering shès, and its distance in matter is very curved, in addition, the β+shè line can also annihilate the radiation.

When the βshè line passes through the substance, its strength is weakened, i.e., it is absorbed by the substance. βshè lines have a continuous energy spectrum, that is, they are composed of single-energy electrons with different energies. The electrons of different energies are different in watts, and the electrons of the energy system are affected by them

The situation of scattered shè is different, and the shè process is also very different. Therefore, the absorption curve of the βshè line is very different from that of the α particle, β the shè degree of the particle in the substance cannot be expressed by the concept of average generation, but only by the maximum generation.

When β particles pass through matter, similar to α particles, they can also ionize and excite atoms and lose energy.

In addition to the energy loss of β particles in the matter by ionization collisions, they can also lose energy through the guò radiation shè process. When a fast electron approaches the nucleus, its velocity decreases rapidly under the action of the coulomb field of the nucleus, and electromagnetic radiation is emitted. This electromagnetic radiation shè is called tough-induced spoke.

When β particles interact with atoms, they not only lose energy, but also change the direction of motion, which is called scattering.

γshè line

The γshè line is an uncharged flow of high-energy photons, so the mechanism of its interaction with matter is different from that of charged particles such as α and β, and the photoelectric effect and the Compton effect can occur, which is basically the same as the Xshè line, but because its energy is much higher than that of the Xshè line, it can also produce electron pair effects.

When a photon interacts with a bound electron in an atom of a substance, γ all the amount there is transferred to the electron, causing it to fly out of the atom and disappear γ photon itself, a process called the photoelectric effect.

When a photon interacts with an atom of a substance, γ a part of the energy is transferred to the electron, causing it to fly out of the atom, and the photon loses energy and changes the direction of motion, this process is called the Compton effect, also known as the Compton scattering shè.

When an γ photon with an energy greater than 1.022 MeV passes through a substance, the γ photon is photonized into one positron and one photoelectron under the action of the Coulomb field of the nucleus, a process called the electron pair effect.

neutron

Neutrons are produced by neutron sources, and neutrons in the zìyóu state are unstable and can decay into protons, emitting a β electron and an antineutrino. Because the energy of neutrons is different, and its interaction with matter is also different, it is often divided into slow neutrons, medium-energy neutrons, fast neutrons and high-energy neutrons according to their energy. Neutrons do not have an electric charge, they interact very little with electrons when they pass through matter, and they mainly interact with the nucleus, and there are two types of interaction between neutrons and nuclei: scattered shè and nuclear reactions. Bullets are the most common interaction between neutrons and nuclei.

Types of nuclear decay

The vast majority of the more than 2,000 nuclides found so far are unstable nuclei. The unstable dìng nucleus spontaneously emits shè lines to change into another nucleus, a process known as nuclear decay. The xìng substances that these nuclides can spontaneously emit shèxìng are called release shèxìng, and the nuclides with this characteristic xìng are called release shèxìng nuclides. Therefore, nuclear decay is also called shèxìng decay. Post-decay is a characteristic nucleus that puts shèxìng nuclides, and in general, is not affected by external conditions such as temperature, pressure, electromagnetic fields, etc.

Nuclear decay can be classified according to the nuclear radiation shè from which it emits, and the most common ones are α decay, β decay, and decay. There is also spontaneous fission, which refers to the spontaneous splitting of an atomic nucleus into two or more nuclei of similar mass. In addition, with the development of nuclear radiation measurement technology, some new decay methods are still being discovered, such as proton decay, 14C double decay, 20Ne decay, decay, etc., of course, these decays are rare. Now we mainly introduce the three decay modes of α, β, and γ.

alpha decay

α decay refers to the process by which shèxìng nuclei and shèα particles decay into another nucleus. In α decay nuclides, only a few nuclides emit α particles, and most of the nuclides emit α particles with several sets of energy. The energy spectrum of α particles is discontinuous and consists of a set of discrete linear spectral lines. Moreover, α decay of shèxìng nuclides in the hair shèα particles are often accompanied by the release of γshè lines.

β decay

β decay refers to the decay of a nuclear that changes the nuclear charge without the same mass. In this process, the nucleus releases an electron or positron, or captures an extra-nuclear orbital electron, whose daughter nucleus and parent nuclei have the same mass, and the nuclear charge number changes by +1 or -1. Thus, β decay includes β-decay (generally represented by β decay), β+ decay, and orbital electron capture (EC).

γ decay

The process by which the nucleus transitions from an excited state to a low-energy state is called γ decay or γ transition. α, β decay process, or when other high-speed particles bombard the nucleus, the nucleus can be in an excited state, so these processes are often accompanied by γshè lines.

Sometimes, when the nucleus transitions from an excited state to a low-energy state, it does not necessarily emit shèγ photons, but directly hands the excited energy to the electrons outside the nucleus, causing it to break away from the atom and become zìyóu electrons, a phenomenon called internal conversion (IC). The emitted electrons are called internal conversion electrons. The transitions between the energy levels of the nucleus can either emit shèγ photons or produce internal conversions.

Put shèxìng

Shèxìng is a natural phenomenon in which the nucleus of an unstable dìng spontaneously emits a certain shè line and transforms into another nucleus. The main decay modes are α decay, β decay, electron trapping, and homogeneous heterogeneous transition, which may release α particles, β+ particles, β-particles, electrons, photons, neutrons, and fission fragments.

Ionized spokes shè

According to the source, ionized radiation shè is divided into natural radiant shè and artificial radiant shè; According to the internal and external radiation shè sources, it is divided into internal shè and external shè; The outer shè comes from the cosmic rays and the shèxìngshè line, and the main ways of the inner shè are ingestion and inhalation. The harmful effects of ionization radiation on the human body can be divided into somatic effects and genetic effects, and the somatic effects appear in the irradiated person himself, such as cancer, cataract, radiotherapy, etc.; Genetic effects are observed in the offspring of the irradiated shè.

Put shèxìng nuclides and radiated shè sources

The nuclides are divided into yusheng nuclides, native nuclides, and artificial nuclides. The nuclides are mainly produced due to the interaction between cosmic rays and the atomic nuclei in the atmosphere and the earth's surface, and only 3H, 7Be, 14C and 22Na need to be paid attention to in the nuclides. The primary nuclides are the natural nuclides that have been stored in the earth's crust since the existence of the earth, and the main primary nuclides that have survived to this day are 40K and 238U and 232Tu. Artificial sources mainly include: artificial sources or processed natural sources produced in nuclear explosions and nuclear energy production, as well as sources used in medical photos and consumer products.

The effects of a nuclear explosion radiate shè

After a nuclear explosion, the fission products, remaining fission material, and structural materials are vaporized in a high-temperature fireball, forming aerosol particles with a strong emitt. The gravity sedimentation of larger aerosol particles within a range of several hundred kilometers from the explosion center is called local sedimentation; Smaller aerosol particles injected into the troposphere settle around the Earth mainly within the same hemisphere, which is called tropospheric sedimentation; The worldwide sedimentation formed by tiny aerosol particles injected into the stratosphere is known as global sedimentation. The main nuclides produced by nuclear explosions that cause exoillumination are: 137Cs and short-lived nuclides 95Zr, 106Ru, 140Ba, 144Ce, 103Ru and 141Ce. The main nuclides that cause exoshishi are: 14C, 137Cs, 90Sr, 106Ru, 144Ce,

3H, 131I, 239, 240, 241Pu, 55Fe, 241Am, and 89Sr.

Medical photo shè

The wide application of various ionized radionuclides and radionuclides in the diagnosis and treatment of medicine has made medical radiation shine in the first place among the artificial irradiation sources received by the public.

Spoke shè danger hài

Mechanism of action:

When the body is exposed to ionizing radiation, it can damage many living substances, especially biological macromolecules, the most important of which is the deoxynucleic acid (DNA) in the nucleus. There are two ways in which ionization radiations act on these living substances: one is that the shè lines act directly on these substances, such as DNA, through ionization and excitation to cause damage. The second is the interaction between the shè line and other atoms or molecules in the cell, especially water molecules, to produce zìyóu groups that cause damage to biological organisms. The former is called the direct action of the shè line, and the latter is called the indirect action of the shè line, and the indirect effect of the low energy transmission line density spokes shè (including all energy Xshè lines and shè line spokes) is dominant.

Mode of action:

According to the relative position of the source of radiation on the human body, the ways of acting on the human body can be divided into external shè, internal shè, shèxìng nuclides staining the body surface and composite shè.

(1) External shè: refers to the irradiated shè caused by the source of the radiant shè located outside the human body. When the radiant shè source is located at a sufficient distance outside the human body, it can cause a more uniform full-body irradiation of the human body, and conversely, the radiant shè source is close to the human body and causes local irradiation.

(2) Neizhao shè: Abnormal amount of shèxìng nuclides into the body is called shèxìng nuclide internal pollution. The radiation caused by the storage of zài and the release of shèxìng nuclides in the human body is called the internal shè. Organs deposited at the source of radiations (abbreviated as S); The organ that is exposed to the radiation shè from the original organ is called the target organ (abbreviated as T).

(3) Contamination of the body surface of shèxìng nuclides: It refers to the contamination of shèxìng nuclides on the surface of the human body (skin or mucous membranes), or the body surface of health, or the body surface of trauma. The contaminated nuclides constitute an external source of contamination, and can still be absorbed into the blood through the body surface to form an internal photo.

In practice, it is often the case that multiple situations coexist at the same time. Just from the point of view of radiation shè damage, it is only a certain way of shè as the main thing.