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In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which an atomic nucleus emits a beta particle, transforming into an isobar of that nuclide. For example, beta decay of a neutron transforms it into a proton by the emission of an electron accompanied by an antineutrino; or, conversely a proton is converted into a neutron by the emission of a positron with a neutrino in so-called positron emission. Neither the beta particle nor its associated (anti-)neutrino exist within the nucleus prior to beta decay, but are created in the decay process. By this process, unstable atoms obtain a more stable ratio of protons to neutrons. The probability of a nuclide decaying due to beta and other forms of decay is determined by its nuclear binding energy. The binding energies of all existing nuclides form what is called the nuclear band or valley of stability. For either electron or positron emission to be energetically possible, the energy release or Q value must be positive.
The neutron is a subatomic particle, symbol
n
or
n0
, which has a neutral charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons behave similarly within the nucleus, and each has a mass of approximately one atomic mass unit, they are both referred to as nucleons. Their properties and interactions are described by nuclear physics. Protons and neutrons are not elementary particles; each is composed of three quarks.
Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions, in addition to the study of other forms of nuclear matter.
A neutrino is a fermion that interacts only via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass is so small (-ino) that it was long thought to be zero. The rest mass of the neutrino is much smaller than that of the other known elementary particles excluding massless particles. The weak force has a very short range, the gravitational interaction is extremely weak due to the very small mass of the neutrino, and neutrinos do not participate in the strong interaction. Thus, neutrinos typically pass through normal matter unimpeded and undetected.
Proton emission is a rare 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 emission, or can occur from the ground state of very proton-rich nuclei, in which case the process is very similar to alpha decay. For a proton to escape a nucleus, the proton separation energy must be negative —the proton is therefore unbound, and tunnels out of the nucleus in a finite time. The rate of proton emission is governed by the nuclear, Coulomb, and centrifugal potentials of the nucleus, where centrifugal potential affects a large part of the rate of proton emission. Half-life of proton emission is affected by the proton energy and its orbital angular momentum. Proton emission is not seen in naturally occurring isotopes; proton emitters can be produced via nuclear reactions, usually using linear particle accelerators.
The Cowan–Reines neutrino experiment was conducted by Washington University in St. Louis alumnus Clyde L. Cowan and Stevens Institute of Technology and New York University alumnus Frederick Reines in 1956. The experiment confirmed the existence of neutrinos. Neutrinos, subatomic particles with no electric charge and very small mass, had been conjectured to be an essential particle in beta decay processes in the 1930s. With neither mass nor charge, such particles appeared to be impossible to detect. The experiment exploited a huge flux of electron antineutrinos emanating from a nearby nuclear reactor and a detector consisting of large tanks of water. Neutrino interactions with the protons of the water were observed, verifying the existence and basic properties of this particle for the first time.
In nuclear physics, double beta decay is a type of radioactive decay in which two neutrons are simultaneously transformed into two protons, or vice versa, inside an atomic nucleus. As in single beta decay, this process allows the atom to move closer to the optimal ratio of protons and neutrons. As a result of this transformation, the nucleus emits two detectable beta particles, which are electrons or positrons.
In spectroscopy, a forbidden mechanism is a spectral line associated with absorption or emission of photons by atomic nuclei, atoms, or molecules which undergo a transition that is not allowed by a particular selection rule but is allowed if the approximation associated with that rule is not made. For example, in a situation where, according to usual approximations, the process cannot happen, but at a higher level of approximation the process is allowed but at a low rate.
p-nuclei (p stands for proton-rich) are certain proton-rich, naturally occurring isotopes of some elements between selenium and mercury inclusive which cannot be produced in either the s- or the r-process.
Gail Catherine McLaughlin is an American nuclear astrophysicist specializing in astrophysical neutrinos and the r-process for nucleosynthesis. She is Distinguished University Professor of Physics at North Carolina State University.
The Astroparticle and Cosmology (APC) laboratory in Paris gathers researchers working in different areas including high-energy astrophysics, cosmology, gravitation, and neutrino physics.
Magda Galula Ericson (born 1929) is a French-Algerian physicist of Tunisian origin. Her experimental pioneering PhD work changed the understanding of critical phenomena near the Curie point and later in her career she has become known for her theoretical development of the Ericson-Ericson Lorentz-Lorenz correction.
Toshiko Yuasa was a Japanese nuclear physicist who worked in France. She was the first Japanese female physicist.
Karsten M. Heeger is a German–American physicist and Eugene Higgins Professor of Physics at Yale University, where he also serves as both chair of the Yale Department of Physics and director of Wright Laboratory. His work is primarily in the area of neutrino physics, focusing on the study of neutrino oscillations, neutrino mass, and dark matter.
Marielle Chartier is a Professor of Particle Physics at the University of Liverpool in England. Her research investigates the phase diagram of nuclear matter using the ALICE experiment at the Large Hadron Collider (LHC) at CERN Her past work includes nuclear structure at the frontiers of the valley of stability.
Natalie Ann Roe is an experimental particle physicist and observational cosmologist, and the Associate Laboratory Director for the Physical Sciences Area at Lawrence Berkeley National Laboratory (LBNL) since 2020. Previously, she was the Physics Division Director for eight years. She has been awarded as the Fellow of American Physical Society (APS) and American Association for the Advancement of Science (AAAS) for her exceptional scientific career and contributions.
Lucia Reining is a German theoretical spectroscopist who works in France as a director of research with the French National Centre for Scientific Research (CNRS), in the Laboratoire des Solides Irradiés at the École Polytechnique.
Eric B. Norman is an American physicist. He is a professor in the graduate school of the University of California, Berkeley.
Felix Hans Boehm was a Swiss-American experimental physicist, known for his research on weak interactions, parity violation, and neutrino physics.
Carla Fröhlich is a Swiss and American nuclear astrophysicist whose research has included the neutrino p-process for nucleosynthesis in supernovae, and the study of multi-messenger astronomy. She is a professor of physics and University Faculty Scholar at North Carolina State University.
References
- 1 2 3 Page personnelle: (Maria) Cristina Volpe, Laboratoire Astroparticule & Cosmologie, retrieved 2023-07-09
- ↑ "Etude des comportements anharmoniques et non-lineaires des vibrations des noyaux atomiques par Maria Cristina Volpe", Theses.fr, retrieved 2023-07-09
- ↑ "Fellows nominated in 2011 by the Division of Nuclear Physics", APS Fellows archive, American Physical Society, retrieved 2023-07-09
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