Nuclear force
The nuclear force (or nucleon-nucleon interaction) is the force between two or more nucleons. It affects the binding of nucleons into nuclei and the scattering of two nucleons. The force depends not only on the distance between two nucleons, but also on their relative velocity, and on their isospin.
There has been a lot of work on understanding and parametrizing the nuclear force. The long-range part of this force is of the form of a Yukawa potential due to the exchange of light mesons, such as the pions.
Sometimes the nuclear force is called the residual strong force, in contrast to the strong interactions which are now understood to arise from quantum chromodynamics. This phrasing was forced during the 1970s due to a change in paradigm. Before that time, the strong nuclear force refererred to the inter-nucleon potential. After the introduction of the quark model, strong interaction came to mean QCD. Whatever the history, the phrase could be misleading today. Since nucleons have no color charge, the nuclear force does not directly involve the force carriers of quantum chromodynamics, the gluons.
History
The nuclear force has been at the heart of nuclear physics ever since the field was born in 1932 with the discovery of the neutron by Chadwick. The traditional goal of nuclear physics is to understand the properties of atomic nuclei in terms of the 'bare' interaction between pairs of nucleons.
The oldest attempt to explain the nature of the nuclear force is due to Yukawa. According to his theory, massive bosons (mesons) mediate the interaction between two nucleons. Although, in the light of QCD, meson theory is no longer perceived as fundamental, the meson exchange concept (where nucleons are assumed to be elementary particles) continues to represent the best working model for a quantitative nucleon-nucleon potential.
Historically, it turned out to be a formidable task to describe the nuclear force just phenomenologically, and it took a quarter of a century to come up with the first semi-empirical quantitative models - in the mid-1950s. Ever since, there has been substancial progress in experiment and theory related to the the nuclear force. Most basic questions were settled in the 1960s and 1970s. In recent years, we could concentrate on the subtelties of this peculiar force, such as charge dependence, the precise value of the πNN coupling constant, improved phase shift analysis, high-precision NN data, high-precision NN potentials, NN scattering at intermediate and high energies, and attempts to derive the nuclear force from QCD.
Main properties of the strong nuclear force
- At typical nucleon separation (1.3×10-15m) it is a very strong attractive force (104 N).
- At much smaller separations between nucleons the force is very powerfully repulsive.
- Beyond about 1.3×10-15m separation, the force exponentially dies off to zero.
- Thus, the strong nuclear force is a very short-range force.
- The strong nuclear force does not depend on electric charge.
- The much smaller Coulomb force between protons has a much larger range and becomes the only significant force between protons when their separation exceeds about 2.5×10-15m.
See also
References
- Gerald Edward Brown and A. D. Jackson, The Nucleon-Nucleon Interaction, (1976) North-Holland Publishing, Amsterdam ISBN 0-7204-0335-9
- R. Machleidt and I. Slaus, The nucleon-nucleon interaction, J. Phys. G 27 (2001) R69 (topical review).
 | This physics-related article is a stub. You can help Wikipedia by expanding it. |