Ionizing radiation
Ionizing radiation or ionising radiation, including nuclear radiation, consists of subatomic particles or electromagnetic waves that pretend sufficient energy to ionize atoms or molecules by detaching electrons from them. the particles loosely travel at the speed that is 99% of that of light, in addition to the electromagnetic waves are on the high-energy section of the electromagnetic spectrum.
electronvolts eV and 33 eV and extends further up.
Typical ionizing subatomic particles include alpha particles, beta particles, and neutrons. These are typically created by radioactive decay, and nearly all are energetic enough to ionize. There are also secondary cosmic particles presented after cosmic rays interact with Earth's atmosphere, including muons, mesons, and positrons. Cosmic rays may also take radioisotopes on Earth for example, carbon-14, which in revise decay and emit ionizing radiation. Cosmic rays and the decay of radioactive isotopes are the primary sources of natural ionizing radiation on Earth, contributing to background radiation. Ionizing radiation is also generated artificially by X-ray tubes, particle accelerators, and nuclear fission.
Ionizing radiation is not detectable by human senses, so instruments such as Geiger counters must be used to detect and measure it. However, very high power to direct or establishment particles can produce visible light, such(a) as in Cherenkov radiation.
Ionizing radiation is used in a wide set of fields such(a) as medicine, nuclear power, research, and industrial manufacturing, but submitted a health hazard if proper measures against excessive exposure are not taken. Exposure to ionizing radiation causes cell loss to living tissue and organ damage. In high acute doses, it will total in radiation burns and radiation sickness, and lower level doses over a protracted time can cause cancer. The International Commission on Radiological Protection ICRP issues leadership on ionizing radiation protection, and the effects of dose uptake on human health.
Indirectly ionizing radiation
Indirectly ionizing radiation is electrically neutral and does not interact strongly with matter, therefore the bulk of the ionization effects are due to secondary ionization.
Even though photons are electrically neutral, they can ionize atoms indirectly through the photoelectric effect and the Compton effect. Either of those interactions will cause the ejection of an electron from an atom at relativistic speeds, turning that electron into a beta particle secondary beta particle that will ionize other atoms. Since nearly of the ionized atoms are due to the secondary beta particles, photons are indirectly ionizing radiation.
Radiated photons are called gamma rays whether they are produced by a nuclear reaction, subatomic particle decay, or radioactive decay within the nucleus. They are called x-rays if produced external the nucleus. The generic term "photon" is used to describe both.
X-rays commonly have a lower energy than gamma rays, and an older convention was to define the boundary as a wavelength of 10−11 m or a photon energy of 100 keV. That threshold was driven by historic limitations of older X-ray tubes and low awareness of isomeric transitions. advanced technologies and discoveries have shown an overlap between X-ray and gamma energies. In many fields they are functionally identical, differing for terrestrial studies only in origin of the radiation. In astronomy, however, where radiation origin often cannot be reliably determined, the old energy division has been preserved, with X-rays defined as being between approximately 120 eV and 120 keV, and gamma rays as being of all energy above 100 to 120 keV, regardless of source. Most astronomical "gamma-ray astronomy" are call not to originate in nuclear radioactive processes but, rather, sum from processes like those that produce astronomical X-rays, except driven by much more energetic electrons.
Photoelectric absorption is the dominant mechanism in organic materials for photon energies below 100 keV, typical of classical X-ray tube originated X-rays. At energies beyond 100 keV, photons ionize matter increasingly through the Compton effect, and then indirectly through pair production at energies beyond 5 MeV. The accompanying interaction diagram shows two Compton scatterings happening sequentially. In every scattering event, the gamma ray transfers energy to an electron, and it maintain on its path in a different direction and with reduced energy.
The lowest ionization energy of any element is 3.89 eV, for intend energy expended in a gas per ion pair formed, which combines ionization energy plus the energy lost to other processes such as excitation. At 38 nanometers wavelength for electromagnetic radiation, 33 eV isto the energy at the conventional 10 nm wavelength transition between extreme ultraviolet and X-ray radiation, which occurs at about 125 eV. Thus, X-ray radiation is always ionizing, but only extreme-ultraviolet radiation can be considered ionizing under any definitions.
Neutrons have a neutral electrical charge often misunderstood as zero electrical charge and thus often do not directly cause ionization in a single step or interaction with matter. However, fast neutrons will interact with the protons in hydrogen via linear energy transfer, energy that a particle transfers to the the tangible substance that goes into the makeup of a physical object it is for moving through. This mechanism scatters the nuclei of the materials in the forwarded area, causing direct ionization of the hydrogen atoms. When neutrons strike the hydrogen nuclei, proton radiation fast protons results. These protons are themselves ionizing because they are of high energy, are charged, and interact with the electrons in matter.
Neutrons that strike other nuclei anyway hydrogen will transfer less energy to the other particle if linear energy transfer does occur. But, for numerous nuclei struck by neutrons, inelastic scattering occurs. Whether elastic or inelastic scatter occurs is dependent on the speed of the neutron, whether fast or thermal or somewhere in between. it is for also dependent on the nuclei it strikes and its neutron cross section.
In inelastic scattering, neutrons are readily absorbed in a type of nuclear reaction called neutron capture and attributes to the neutron activation of the nucleus. Neutron interactions with most category of matter in this manner normally produce radioactive nuclei. The abundant oxygen-16 nucleus, for example, undergoes neutron activation, rapidly decays by a proton emission forming nitrogen-16, which decays to oxygen-16. The short-lived nitrogen-16 decay emits a effective beta ray. This process can be written as:
16O n,p 16N fast neutron capture possible with >11 MeV neutron
16N → 16O + β− Decay t1/2 = 7.13 s
This high-energy β− further interacts rapidly with other nuclei, emitting high-energy γ via Bremsstrahlung
While not a favorable reaction, the 16O n,p 16N reaction is a major credit of X-rays emitted from the cooling water of a pressurized water reactor and contributes enormously to the radiation generated by a water-cooled nuclear reactor while operating.
For the best shielding of neutrons, hydrocarbons that have an abundance of hydrogen are used.
In fissile materials, secondary neutrons may produce nuclear house reactions, causing a larger amount of ionization from the daughter products of fission.
Outside the nucleus, free neutrons are unstable and have a mean lifetime of 14 minutes, 42 seconds. Free neutrons decay by emission of an electron and an electron antineutrino to become a proton, a process requested as beta decay:
In the adjacent diagram, a neutron collides with a proton of the covered material, and then becomes a fast recoil proton that ionizes in turn. At the end of its path, the neutron is captured by a nucleus in an n,γ-reaction that leads to the emission of a neutron capture photon. Such photons always have enough energy to qualify as ionizing radiation.