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Encyclopedia > Double electron capture
Nuclear processes
Radioactive decay processes

Nucleosynthesis Radioactive decay is the set of various processes by which unstable atomic nuclei (nuclides) emit subatomic particles (radiation). ... Alpha decay is a form of radioactive decay in which an atomic nucleus ejects an alpha particle and transforms into a nucleus with mass number 4 less and atomic number 2 less. ... In nuclear physics, beta decay (sometimes called neutron decay) is a type of radioactive decay in which a beta particle (an electron or a positron) is emitted. ... Cluster decay is the nuclear process in which a radioactive atom emits a cluster of neutrons and protons. ... In the process of beta decay unstable nuclei decay by converting a neutron in the nucleus to a proton and emitting an electron and anti-neutrino. ... Electron capture is a decay mode for chemical elements that will occur when there are too many protons in the nucleus of an atom, and there isnt enough energy to emit a positron; however, it continues to be a viable decay mode for radioactive elements that can decay by... This article is about electromagnetic radiation. ... This article is about the nuclear process. ... Internal conversion or isomeric transition is the act of returning from an excited state by an atom or molecule. ... Neutron emission is a type of radioactive decay in which an atom contains excess neutrons and a neutron is simply ejected from the nucleus. ... Positron emission is a type of beta decay, sometimes referred to as beta plus (β+). In beta plus decay, a proton is converted to a neutron via the weak nuclear force and a beta plus particle (a positron) and a neutrino are emitted. ... Proton emission (also known as proton radioactivity) is a type of radioactive decay in which a proton is ejected from a nucleus. ... 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 amu (elements near ruthenium). ... Nucleosynthesis is the process of creating new atomic nuclei either by nuclear fusion or nuclear fission. ...

  • Neutron Capture
    • The R-process
    • The S-process
  • Proton capture:
    • The P-process

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 has to occur when the mass of the nuclide of (A, Z-2) is lower. The R process (R for rapid) is a neutron capture process for radioactive elements which occurs in high neutron density, high temperature conditions. ... The S process (S for slow) is a neutron capture process in the decay of radioactive elements that occurs in lower neutron density, lower temperature conditions. ... The p process was believed to be a proton capture process which occurrs during supernovae explosions. ... In physics, the decay mode describes a particular way a particle decays. ... A stylized representation of a lithium atom. ... In physics a nucleon is a collective name for the two baryons: the neutron and the proton. ... The atomic number (Z) is a term used in chemistry and physics to represent the number of protons found in the nucleus of an atom. ...

In this mode of decay, two of the orbital electrons are captured by two protons in the nucleus, forming two neutrons. Two neutrinos are emitted in the process. Since the protons are changed to neutrons, the number of neutrons increases by 2, the number of protons Z decreases by 2, and the atomic mass A remains unchanged. By changing the number of protons, double electron capture transforms the nuclide into a new element. Properties The electron is a fundamental subatomic particle which carries a negative electric charge. ... Properties In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ... Properties In physics, the neutron is a subatomic particle with no net electric charge and a mass of 939. ... The neutrino is an elementary particle. ... The atomic mass of a chemical element (also known as the relative atomic mass or average atomic mass or atomic weight) is the average atomic mass of all the chemical elements isotopes as found in a particular environment, weighted by isotopic abundance. ... Isotopes are atoms of a chemical element whose nuclei have the same atomic number, Z, but different atomic weights, A. The word isotope, meaning at the same place, comes from the fact that isotopes are located at the same place on the periodic table. ... A chemical element, often called simply element, is a chemical substance that cannot be divided or changed into other chemical substances by any ordinary chemical technique. ...


In most of cases this decay mode is masked by more probable modes (single electon capture etc.), but when all these modes are forbidden or strongly suppressed, double electron capture becames the main mode of decay. There exist 35 naturally occurring isotopes that can undergo double electron capture. However, there are no confirmed observations of this process. The one reason is that the probability of double electron capture is enormously small (the theoretical predictions of half-lives for this mode lies well above 1020 years). The second reason is that the only detectable particles created in this process are X-rays and Auger-electrons that are emitted by the excited atomic shell. In the range of their energies (~1-10 keV), the background is usually high. Thus, the experimental detection of double electron capture is more difficult than that for double beta decay. Half-Life For a quantity subject to exponential decay, the half-life is the time required for the quantity to fall to half of its initial value. ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... Kev is a derogatory term originating in the United Kingdom and applying to a yobbish young man or boy. ... In the process of beta decay unstable nuclei decay by converting a neutron in the nucleus to a proton and emitting an electron and anti-neutrino. ...

If the mass difference between the mother and daughter atoms is more than two masses of electron (1.022 MeV), the energy released in the process is enough to allow another mode of decay: electron capture with positron emission. It occurs simultaneously with double electron capture, their branching ratio depending on nuclear properties. When the mass difference is more than four electron masses (2.044 MeV), the third mode - double positron decay - is allowed. Only 6 naturally occurring nuclides can decay via these three modes simultaneously. An electronvolt (symbol: eV) is the amount of energy gained by a single unbound electron when it falls through an electrostatic potential difference of one volt. ... This is a technical term in particle physics and nuclear physics. ...

Neutrinoless double electron capture

The above described process with capture of two electrons and emission of two neutrinos (two-neutrino double electron capture) is allowed by the Standard Model of particle physics: no conservation laws (including lepton number conservation) are violated. However, if the lepton number is not conserved, another kind of the process can occur: the so-called neutrinoless double electron capture. In this case, two electrons are captured by nucleus, but neutrinos are not emitted. The energy released in this process is carried away by an internal bremsstrahlung gamma quantum. This mode of decay has also never been observed experimentally. The Standard Model of Fundamental Particles and Interactions The Standard Model of particle physics is a theory which describes the strong, weak, and electromagnetic fundamental forces, as well as the fundamental particles that make up all matter. ... Particles erupt from the collision point of two relativistic (100GeV) gold ions in the STAR detector of the Relativistic Heavy Ion Collider. ... Bremsstrahlung   listen?, German for braking radiation, is electromagnetic radiation produced by the acceleration of a charged particle, such as an electron, when deflected by another charged particle, such as an atomic nucleus. ... This article is about electromagnetic radiation. ...


See also

  Results from FactBites:
Electron capture - Wikipedia, the free encyclopedia (387 words)
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 a viable decay mode for radioactive isotopes that can decay by positron emission.
In this case, one of the orbital electrons, usually from the K or L electron shell (K-electron capture, also K-capture, or L-electron capture, L-capture), is captured by a proton in the nucleus, forming a neutron and a neutrino.
Since the proton is changed to a neutron, the number of neutrons increases by 1, the number of protons decreases by 1, and the atomic mass number remains unchanged.
Atomic, Molecular & Optical Sciences: Publications: M.H. Prior (1725 words)
Double photo-ionization of He is a simple example of the extensive, and largely undeveloped study of many particle dynamics in AMO physics, and is a bridge between single particle and multiple particle excitation.
Since electron rearrangement is central to nearly all reactive processes, basic studies of orientation dependent electron transfer form a useful window into the correlation between structure and collision dynamics.
Using the techniques of electron and ion momentum spectroscopy, we have measured the complete emission patterns of core photoelectrons emitted from the C and O atoms for any (and all) relative orientations of the CO molecular axis and the linearly polarization of the incident soft X-ray photons.
  More results at FactBites »



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