Information about Alpha Emission
| Nuclear physics |
| Key topics |
| Radioactive decay Nuclear fission Nuclear fusion |
| Classical decays |
| Alpha decay Beta decay Gamma radiation Cluster decay |
| Advanced decays |
| Double beta decay Double electron capture Internal conversion Isomeric transition |
| Emission processes |
| Neutron emission Positron emission Proton emission |
| Capturing |
| Electron capture Neutron capture R S P Rp |
| Fission |
| Spontaneous fission Spallation Cosmic ray spallation Photodisintegration |
| Nucleosynthesis |
| Stellar Nucleosynthesis Big Bang nucleosynthesis Supernova nucleosynthesis |
| Scientists |
| Marie Curie others |
An alpha particle is identical to a helium nucleus, and both mass number and atomic number are the same. Alpha decay is a form of nuclear fission where the parent atom splits into two daughter products. Alpha decay is fundamentally a quantum tunneling process. Unlike beta decay, alpha decay is governed by the strong nuclear force.
Alpha particles have a typical kinetic energy of 5 MeV (that is ≈0.13% of their total energy, i.e. 110 TJ/kg) and a speed of 15,000 km/s. This corresponds to a speed of around 0.05c. Because of their relatively large mass, +2 charge and relatively low velocity, they are very likely to interact with other atoms and lose their energy, so they are effectively absorbed within a few centimeters of air.
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Alpha source beneath a radiation detector
Most of the helium produced on Earth comes from the alpha decay of underground deposits of minerals containing uranium or thorium. The helium is brought to the surface as a by-product of natural gas production.
History
By 1928, George Gamow had solved the theory of the alpha decay via tunneling. The alpha particle is trapped in a potential well by the nucleus. Classically, it is forbidden to escape, but according to the then newly discovered principles of Quantum mechanics, it has a tiny (but non-zero) probability of "tunneling" through the barrier and appearing on the other side to escape the nucleus.Uses
Americium-241 is used in smoke detectors. The alpha particles ionize air between a small gap, leading to a small current that can be easily interrupted by smoke particles.Alpha decay can provide a safe power source for radioisotope thermoelectric generators used for space probes and artificial heart pacemakers. Alpha decay is much more easily shielded against than other forms of radioactive decay. Plutonium-238, for example, requires only 2.5 mm of lead shielding to protect against unwanted radiation.
Toxicity
Because they are heavy and charged, alpha particles tend to have a very short mean free path, and therefore lose their kinetic energy within a short distance of their source. This can result in several MeV being deposited in a relatively small area. If they penetrate live tissue, this can cause significant cellular damage. Generally, external alpha radiation is not harmful because alpha particles are completely absorbed by a few centimeters of air. Even touching an alpha source is usually not harmful; the thin layer of dead skin cells in the outermost layer of the skin will absorb them. However, if a substance radiating alpha particles is ingested, inhaled by, injected into, or introduced through the skin (shrapnel, corrosive chemicals) into an organism it may result in a high dose to that area.Radon is a naturally occurring, radioactive gas found in soil, rock, and sometimes groundwater. When radon gas is inhaled, some of the radon particles stick to the inner lining of the lung. The particles that remain continue to decay over time, emitting alpha particles which may damage cells in the lung tissue.[1]. The death of Marie Curie at age 66 from leukemia was likely caused by prolonged exposure to high doses of ionizing radiation. Curie worked extensively with Radium, which decays into Radon[2], along with other radioactive materials that emit beta and gamma rays. Shrapnel deposited in the body from depleted uranium poses another such internal risk of alpha particle radiation dose.
The 2006 assassination of Russian dissident Alexander Litvinenko is thought to have been caused by poisoning with Polonium-210, an alpha emitter.
References
1. ^ EPA Radiation Information: Radon. October 6 2006, [1], Accessed Dec. 6 2006
2. ^ Health Physics Society, "Did Marie Curie die of a radiation overexposure?" [2]
2. ^ Health Physics Society, "Did Marie Curie die of a radiation overexposure?" [2]
Nuclear processes | |
|---|---|
| Radioactive decay | Alpha decay Beta decay Gamma radiation Cluster decay Double beta decay Double electron capture Internal conversion Isomeric transition Spontaneous fission |
| Other processes | Emission processes: Neutron emission Positron emission Proton emission Capturing: Electron capture Neutron capture |
| Stellar nucleosynthesis | pp-Chain CNO cycle α process Triple-α Carbon burning Ne burning O burning Si burning R-process S-process P-process Rp-process |
Nuclear physics is the branch of physics concerned with the nucleus of the atom. It has three main aspects: probing the fundamental particles (protons and neutrons) and their interactions, classifying and interpreting the properties of nuclei, and providing technological advances.
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Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. This decay, or loss of energy, results in an atom of one type, called the parent nuclide
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Nuclear fission is the splitting of the nucleus of an atom into parts (lighter nuclei) often producing photons (in the form of gamma rays), free neutrons and other subatomic particles as by-products.
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nuclear fusion is the process by which multiple atomic particles join together to form a heavier nucleus. It is accompanied by the release or absorption of energy. Iron and nickel nuclei have the largest binding energies per nucleon of all nuclei and therefore are the most stable.
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beta decay is a type of radioactive decay in which a beta particle (an electron or a positron) is emitted. In the case of electron emission, it is referred to as "beta minus" (β−), while in the case of a positron emission as "beta plus" (β+).
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Gamma rays or gamma-ray (denoted as γ) are forms of electromagnetic radiation (EMR) or light emissions of a specific frequency produced from sub-atomic particle interaction, such as electron-positron annihilation and..... Click the link for more information.
Cluster decay is the nuclear process in which a radioactive atom emits a cluster of neutrons and protons. While this term technically includes alpha decay, they are usually kept separate because the latter is much more common.
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Emission processes: Neutron emission Positron emission Proton emission
Capturing: Electron capture Neutron capture
Stellar nucleosynthesis pp-Chain CNO cycle α process Triple-α Carbon burning Ne burning O burning Si burning R-process S-process P-process
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Capturing: Electron capture Neutron capture
Stellar nucleosynthesis pp-Chain CNO cycle α process Triple-α Carbon burning Ne burning O burning Si burning R-process S-process P-process
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Double electron capture is a decay mode of atomic nucleus. For a nuclide (A, Z) with number of nucleons A and atomic number Z, double electron capture is only possible if the mass of the nuclide of (A, Z-2) is lower.
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Internal conversion is a radioactive decay process where an excited nucleus interacts with an electron in one of the lower electron shells, causing the electron to be emitted from the atom.
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Isomeric transition is a radioactive decay process that occurs in an atom where the nucleus is in an excited meta state (e.g. following the emission of an alpha or beta particle).
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Neutron emission is a type of radioactive decay in which an atom contains excess neutrons and a neutron is simply ejected from the nucleus. Two examples of isotopes which emit neutrons are helium-5 and beryllium-13.
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Positron emission is a type of beta decay, sometimes referred to as "beta plus" (β+). In beta plus decay, a proton is converted, via the weak force, to a neutron, a positron (also known as the "beta plus particle", the antimatter counterpart of an electron),
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Proton emission (also known as proton radioactivity) is a type of radioactive decay in which a proton is ejected from a nucleus. Proton emission can occur from high-lying excited states in a nucleus following a beta decay, in which case the process is known as beta-delayed proton
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Electron capture (sometimes called Inverse Beta Decay) is a decay mode for isotopes that will occur when there are too many protons in the nucleus of an atom and insufficient energy to emit a positron; however, it continues to be an inviable decay mode for radioactive
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Neutron capture is a kind of nuclear reaction in which an atomic nucleus collides with one or more neutrons and they merge to form a heavier nucleus. Since neutrons have no electric charge, they can enter a nucleus more easily than charged particles which are repelled by
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The r-process is a nucleosynthesis process occurring in core-collapse supernovae (see also supernova nucleosynthesis) responsible for the creation of approximately half of the neutron-rich atomic nuclei that are heavier than iron.
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The S-process or slow-neutron-capture-process is a nucleosynthesis process that occurs at relatively low neutron density and intermediate temperature conditions in stars. Under these conditions the rate of neutron capture by atomic nuclei is slow relative to the rate of radioactive
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The p-process is a nucleosynthesis process occurring in core-collapse supernovae (see also supernova nucleosynthesis) responsible for the creation of some proton-rich atomic nuclei heavier than iron.
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The rp-process (rapid proton capture process) consists of consecutive proton captures onto seed nuclei to produce heavier elements[1]. It is a nucleosynthesis process and, along with the s process and the r process, may be responsible for the generation of many of the
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Spontaneous fission (SF) is a form of radioactive decay characteristic of very heavy isotopes, and is theoretically possible for any atomic nucleus whose mass is greater than or equal to 100 u (elements near ruthenium).
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In general, spallation is a process in which fragments of material (spall) are ejected from a body due to impact or stress. In nuclear physics, it is the process in which a heavy nucleus emits a large number of nucleons as a result of being hit by a high-energy proton, thus greatly
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Cosmic ray spallation is a form of naturally occurring nuclear fission and nucleosynthesis. It refers to the formation of elements from the impact of cosmic rays on an object.
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Photodisintegration is a physical process in which extremely high energy gamma rays interact with an atomic nucleus and cause it to enter an excited state, which immediately decays into two or more daughter nuclei.
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Nucleosynthesis is the process of creating new atomic nuclei from preexisting nucleons (protons and neutrons). The primordial nucleons themselves were formed from the quark-gluon plasma of the Big Bang as it cooled below ten million degrees.
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Stellar nucleosynthesis is the collective term for the nuclear reactions taking place in stars to build the nuclei of the heavier elements. (For other such processes, see nucleosynthesis.
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In physical cosmology, Big Bang nucleosynthesis (or primordial nucleosynthesis) refers to the production of nuclei other than those of H-1 (i.e. the normal, light isotope of hydrogen, whose nuclei consist of a single proton each) during the early phases of the
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Supernova nucleosynthesis refers to the production of new chemical elements inside supernovae. It occurs primarily due to explosive nucleosynthesis during explosive oxygen burning and silicon burning [1].
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Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. This decay, or loss of energy, results in an atom of one type, called the parent nuclide
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