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Encyclopedia > Nuclear physics
Nuclear physics
Nuclear fission
Nuclear fusion
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## Contents

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 3Ã—3 matrix representation of P would have determinant equal to â€“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

### 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

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 â€“ 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 â€“ 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). ...

 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. ...

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. This is a controlled nuclear chain reaction in the opposite of an uncontrolled nuclear chain reaction in nuclear bombs. The nuclear power plants in the future will be fusion reactors which do not crack heavy atomic nucleus, but fuses light atomic nucleus.
 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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