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Encyclopedia > Nuclear physics
Nuclear physics
Radioactive decay
Nuclear fission
Nuclear fusion
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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. Image File history File links CNO_Cycle. ... Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. ... For the generation of electrical power by fission, see Nuclear power plant. ... The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing sustainable fusion power. ... Alpha decay Alpha decay is a type of radioactive decay in which an atom emits an alpha particle (two protons and two neutrons bound together into a particle identical to a helium nucleus) and transforms (or decays) into an atom with a mass number 4 less and atomic number 2... 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. ... This article is about electromagnetic radiation. ... 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. ... Double electron capture is a decay mode of atomic nucleus. ... . 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. ... 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. ... Electron capture is a decay mode for isotopes 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 isotopes that can decay by positron... The process of neutron capture can proceed in two ways - as a rapid process (an r-process) or a slow process (an s-process). ... The R process (R for rapid) is a neutron capture process for radioactive elements which occurs in high neutron density, high temperature conditions. ... This article or section does not cite its references or sources. ... 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. ... The rp process (rapid proton capture process) consists of consecutive proton captures onto seed nuclei to produce heavier elements. ... 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). ... In general, spallation is a process in which fragments of material are ejected from a body due to impact or stress. ... Cosmic ray spallation is a form of naturally occuring nuclear fission and nucleosynthesis. ... Photodisintegration is a physics process in which extremely high energy Gamma rays impact an atomic nucleus and cause it to break apart in a nuclear fission reaction. ... Nucleosynthesis is the process of creating new atomic nuclei from preexisting nucleons (protons and neutrons). ... Cross section of a red giant showing nucleosynthesis and elements formed Stellar nucleosynthesis is the collective term for the nuclear reactions taking place in stars to build the nuclei of the heavier elements. ... In cosmology, Big Bang nucleosynthesis (or primordial nucleosynthesis) refers to the production of nuclei other than H-1, the normal, light hydrogen, during the early phases of the universe, shortly after the Big Bang. ... Supernova nucleosynthesis refers to the production of new chemical elements inside supernovae. ... For the SI unit of radioactivity, see Becquerel. ... This article is about the chemist and physicist. ... Pierre Curie (May 15, 1859 – died April 19, 1906) was a French physicist, a pioneer in crystallography, magnetism, piezoelectricity and radioactivity. ... Hans Albrecht Bethe (pronounced bay-tuh; July 2, 1906 – March 6, 2005), was a German-American physicist who won the Nobel Prize in Physics in 1967 for his work on the theory of stellar nucleosynthesis. ... A magnet levitating above a high-temperature superconductor demonstrates the Meissner effect. ... The nucleus of an atom is the very small dense region, of positive charge, in its centre consisting of nucleons (protons and neutrons). ... For other uses, see Atom (disambiguation). ... In particle physics, an elementary particle is a particle of which other, larger particles are composed. ... For other uses, see Proton (disambiguation). ... This article or section does not adequately cite its references or sources. ...

Contents

Forces

Nuclei are bound together by a strong force. The strong force acts over a very short range and causes an attraction between nucleons (protons and neutrons). The strong nuclear force is so named because it is significantly larger in magnitude than the other fundamental forces (electroweak, electromagnetic and gravitational). The strong force is highly attractive at only very small distances which, combined with repulsion between protons due to the electromagnetic force, allows the nucleus to be stable. The strong force felt between nucleons arises due to the exchange of gluons. The study of the strong force is dealt with by quantum chromodynamics (QCD). The strong nuclear force or strong interaction (also called color force or colour force) is a fundamental force of nature which affects only quarks and antiquarks, and is mediated by gluons in a similar fashion to how the electromagnetic force is mediated by photons. ... For alternative meanings see proton (disambiguation). ... Properties In physics, the neutron is a subatomic particle with no net electric charge and a mass of 940 MeV/c² (1. ... In physics, the electroweak theory presents a unified description of two of the four fundamental forces of nature: electromagnetism and the weak nuclear force. ... In physics, the electromagnetic force is the force that the electromagnetic field exerts on electrically charged particles. ... This article covers the physics of gravitation. ... In physics a nucleon is a collective name for two baryons: the neutron and the proton. ... In physics, gluons are the bosonic particles which are responsible for the strong nuclear force. ... Quantum chromodynamics (abbreviated as QCD) is the theory of the strong interaction (color force), a fundamental force describing the interactions of the quarks and gluons found in hadrons (such as the proton, neutron or pion). ...

Nuclear models

Nucleons in the nucleus move about in a potential energy well which they themselves create arising from their interaction with, and movement with respect to, each other. Nucleons can interact with each other via 2-body, 3-body or multiple-body forces. The fact that many nucleons interact with each other in a complicated way makes the nuclear many-body problem difficult to solve. This article is about the many-body problem in quantum mechanics. ...


There broadly exists two types of nuclear models which attempt to predict and understand characteristics of nuclei. These are microscopic and macroscopic nuclear models. Microscopic nuclear models approximate the potential which the nucleons create in the nucleus. Individual interactions are combined as linear sums of potentials. Almost all models use a central potential plus a spin orbit potential. The difference between models is then defined by the 3-body potential used, and/or the shape of the central potential. The form of this potential is then inserted into the Schrodinger equation. Solution of the Schrödinger equation then yields the nuclear wavefunction, spin, parity and excitation energy of individual levels. The form of the potential used to determine these nuclear properties indicates the type of microscopic model. The shell model and deformed shell model (Nilsson model) are two examples of microscopic nuclear models. In physics, spin refers to the angular momentum intrinsic to a body, as opposed to orbital angular momentum, which is the motion of its center of mass about an external point. ... This box:      For a non-technical introduction to the topic, please see Introduction to quantum mechanics. ... A wave function is a mathematical tool that quantum mechanics uses to describe any physical system. ... In physics, a parity transformation (also called parity inversion) is the simultaneous flip in the sign of all spatial coordinates: A 3×3 matrix representation of P would have determinant equal to –1, and hence cannot reduce to a rotation. ... After absorbing energy, an electron may jump from the ground state to a higher energy excited state. ... In nuclear physics, the nuclear shell model is a model of the atomic nucleus. ...


Macroscopic nuclear models attempt to describe such attributes as the nuclear size, shape and surface diffuseness. Rather than calculating individual levels, macroscopic models predict nuclear radii, degree of deformation and diffuseness parameter. A simple approximation for the nuclear radius is that it is proportional to the cube root of the nuclear mass.


R propto A^{1/3}


This implies that all nuclei are spherical and their radius is directly proportional to the cube root of their volume (volume of a sphere = 4 / 3πR3). Nuclei can also exist in a deformed shape and thus a degree of deformation ,β2, can be included to take this into account. The fact that the nucleus may not be entirely incompressible is also considered by the diffuseness parameter δ. An example of a macroscopic model is the droplet model of Myers and Schmidt. In mathematics, an incompressible surface is a kind of two-dimensional surface inside of a 3-manifold. ...


Some quite successful attempts have been made to combine the microscopic and macroscopic models together. These so called mic-mac models begin with a nuclear potential, solve the Schrödinger equation and proceed to predict macroscopic nuclear parameters.


Protons and neutrons

Protons and neutrons are fermions, with different values of the isospin quantum number, so two protons and two neutrons can share the same space wave function. In the rare case of a hypernucleus, a third baryon called a hyperon, with a different value of the strangeness quantum number can also share the wave function. Fermions, named after Enrico Fermi, are particles which form totally-antisymmetric composite quantum states. ... Isospin (isotopic spin, isobaric spin) is a physical quantity which is mathematically analogous to spin. ... Quantum numbers describe values of conserved quantity in the dynamics of the quantum system. ... A wave function is a mathematical tool that quantum mechanics uses to describe any physical system. ... A Hypernucleus is a nucleus which contains at least one hyperon in addition to nucleons. ... Combinations of three u, d or s-quarks with a total spin of 3/2 form the so-called baryon decuplet. ... In particle physics, a hyperon is any subatomic particle which is a baryon (and hence a hadron and a fermion) with non-zero strangeness, but with zero charm and zero bottomness. ... In particle physics, strangeness, denoted as , is a property of particles, expressed as a quantum number for describing decay of particles in strong and electro-magnetic reactions, which occur in a short period of time. ...


Nuclear activity

Alpha decay

Main article: Alpha decay

Alpha decay Alpha decay is a type of radioactive decay in which an atom emits an alpha particle (two protons and two neutrons bound together into a particle identical to a helium nucleus) and transforms (or decays) into an atom with a mass number 4 less and atomic number 2...

Beta decay

Main article: Beta decay

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. ...

Gamma decay

Main article: Gamma decay

This article is about electromagnetic radiation. ...

Fission

Main article: Nuclear fission

For the generation of electrical power by fission, see Nuclear power plant. ...

Fusion

Main article: Nuclear fusion

The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing sustainable fusion power. ...

History

The binding energies of the protons and neutrons are on the order of 1% of their relativistic rest masses, so non-relativistic quantum mechanics can be used with errors usually smaller than those from other approximations. Once the chemists of the 18th century had elucidated the chemical elements, the rules governing their combinations in matter, and their systematic classification (Mendeleev's periodic table of elements) and John Dalton had, in 1803, applied Democritus's idea of atom to them, it was natural that the next step would be a study of the fundamental properties of individual atoms of the various elements, an activity that we would today classify as atomic physics. These studies led to the discovery in 1896 by Becquerel of the radioactivity of certain species of atoms and to the further identification of radioactive substances by the Curies in 1898. Ernest Rutherford next took up the study of radiation and its properties; once he had achieved an understanding of the nature of the radioactivity, he turned around and used radiated particles to probe the atoms themselves. In the process he proposed in 1911 the existence of the atomic nucleus, the confirmation of which (through the painstaking experiments of Geiger and Marsden) provided a new branch of science, nuclear physics. Two-dimensional analogy of space-time curvature described in General Relativity. ... For a generally accessible and less technical introduction to the topic, see Introduction to quantum mechanics. ... A chemist is a scientist who specializes in chemistry. ... Mendeleyevs portrait by Ilya Repin. ... The periodic table of the chemical elements, also called the Mendeleev periodic table, is a tabular display of the known chemical elements. ... ‎ Democritus (Greek: ) was a pre-Socratic Greek materialist philosopher (born at Abdera in Thrace ca. ... Properties For alternative meanings see atom (disambiguation). ... Atomic physics (or atom physics) is the field of physics that studies atoms as isolated systems comprised of electrons and an atomic nucleus. ... For other uses, see Becquerel (disambiguation). ... Radioactivity may mean: Look up radioactivity in Wiktionary, the free dictionary. ... The curie (symbol Ci) is a former unit of radioactivity, defined as 3. ... Ernest Rutherford, 1st Baron Rutherford of Nelson OM PC FRS (30 August 1871 – 19 October 1937), widely referred to as Lord Rutherford, was a chemist (B.Sc. ... The nucleus of an atom is the very small dense region, of positive charge, in its centre consisting of nucleons (protons and neutrons). ... Johannes (Hans) Wilhelm Geiger (September 30, 1882 – September 24, 1945) was a German physicist. ... Sir Ernest Marsden (1888 - 1970), was a British-New Zealand physicist. ...


Following Rutherford's work, physicists around the world began trying to "split" the atom. The first to achieve this were two of Rutherford's students, John Cockcroft and Ernest Walton, who divided an atom using a particle accelerator in 1932. In 1938, the German physicists Otto Hahn and Errol Von Straussenberg conducted the first successful experiment in nuclear fission. See also: John Cockroft (politician) Sir John Douglas Cockcroft (May 27, 1897 - September 18, 1967) was a British physicist. ... Ernest Thomas Sinton Walton (October 6, 1903 – June 25, 1995) was an Irish physicist and Nobel laureate for his work with John Cockcroft with atom-smashing experiments done at Cambridge University in the early 1930s. ... Atom Smasher redirects here. ... Otto Hahn and Lise Meitner, 1913, at the KWI for Chemistry in Berlin Otto Hahn (March 8, 1879 – July 28, 1968) was a German chemist and received the 1944 Nobel Prize in Chemistry. ... For the generation of electrical power by fission, see Nuclear power plant. ...


In the 1940s and 1950s, it was discovered that there was yet another level of structure even more fundamental than the nucleus, which is itself composed of protons and neutrons. Thus nuclear physics can be regarded as the descendant of chemistry and atomic physics and in turn the progenitor of particle physics. For other uses, see Proton (disambiguation). ... This article or section does not adequately cite its references or sources. ... For other uses, see Chemistry (disambiguation). ... Atomic physics (or atom physics) is the field of physics that studies atoms as isolated systems comprised of electrons and an atomic nucleus. ... Thousands of particles explode from the collision point of two relativistic (100 GeV per nucleon) gold ions in the STAR detector of the Relativistic Heavy Ion Collider. ...


Experiments with nuclei continue to contribute to the understanding of basic interactions. Investigation of nuclear properties and the laws governing the structure of nuclei is an active and productive area of research. Practical applications—nuclear power, smoke detectors, cardiac pacemakers, medical imaging devices, and so on—have become common. This article is about applications of nuclear fission reactors as power sources. ... A smoke detector or smoke alarm is a device that detects smoke and issues an alarm to alert nearby people that there is a potential fire. ... A pacemaker, scale in centimeters A pacemaker (or artificial pacemaker, so as not to be confused with the hearts natural pacemaker) is a medical device which uses electrical impulses, delivered by electrodes contacting the heart muscles, to regulate the beating of the heart. ... Medical imaging designates the ensemble of techniques and processes used to create images of the human body (or parts thereof) for clinical purposes (medical procedures seeking to reveal, diagnose or examine disease) or medical science (including the study of normal anatomy and function). ...


See also

Physics Portal

Image File history File links Portal. ... For the generation of electrical power by fission, see Nuclear power plant. ... The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing sustainable fusion power. ... Most nuclear reactors use a chain reaction to induce a controlled rate of nuclear fission in fissile material, releasing both energy and free neutrons. ...

References

Image File history File links Question_book-3. ...

External links

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  Results from FactBites:
 
Nuclear physics (1674 words)
The reason why nuclear power plants do not exploses is that there are control rods to control the number of the neutrons in the reactor.
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Nuclear physics - Wikipedia, the free encyclopedia (662 words)
Nuclear physics is the branch of physics concerned with the nucleus of the atom.
Thus nuclear physics can be regarded as the descendant of chemistry and atomic physics and in turn the progenitor of particle physics.
Investigation of nuclear properties and the laws governing the structure of nuclei is an active and productive area of research, and practical applications, such as nuclear power, smoke detectors, cardiac pacemakers, and medical imaging devices, have become common.
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