The nuclear magneton (symbol ) is a
physical constant of
magnetic moment
In electromagnetism, the magnetic moment or magnetic dipole moment is the combination of strength and orientation of a magnet or other object or system that exerts a magnetic field. The magnetic dipole moment of an object determines the magnitude ...
, defined in
SI units by:
and in
Gaussian CGS units by:
where:
* is the
elementary charge
The elementary charge, usually denoted by , is a fundamental physical constant, defined as the electric charge carried by a single proton (+1 ''e'') or, equivalently, the magnitude of the negative electric charge carried by a single electron, ...
,
* is the
reduced Planck constant
The Planck constant, or Planck's constant, denoted by h, is a fundamental physical constant of foundational importance in quantum mechanics: a photon's energy is equal to its frequency multiplied by the Planck constant, and the wavelength of a ...
,
* is the
proton
A proton is a stable subatomic particle, symbol , Hydron (chemistry), H+, or 1H+ with a positive electric charge of +1 ''e'' (elementary charge). Its mass is slightly less than the mass of a neutron and approximately times the mass of an e ...
rest mass, and
* is the
speed of light
The speed of light in vacuum, commonly denoted , is a universal physical constant exactly equal to ). It is exact because, by international agreement, a metre is defined as the length of the path travelled by light in vacuum during a time i ...
Its
CODATA recommended value is:
In
Gaussian CGS units, its value can be given in convenient units as
The nuclear magneton is the natural unit for expressing magnetic dipole moments of heavy particles such as
nucleons and
atomic nuclei.
Due to neutrons and protons having internal structure and not being
Dirac particles, their magnetic moments differ from :
: ''μ'' = ''μ''
: ''μ'' = ''μ''
The magnetic dipole moment of the electron, which is much larger as a consequence of much larger
charge-to-mass ratio, is usually expressed in units of the
Bohr magneton, which is calculated in the same fashion using the electron mass. The result is larger than by a factor equal to the proton-to-electron mass ratio, about 1836.
See also
*
Nucleon magnetic moment
References
External links
* {{cite web , url=https://physics.nist.gov/cgi-bin/cuu/Value?mun%7Csearch_for=nuclear+magneton , title=Nuclear magneton , publisher=
NIST
The National Institute of Standards and Technology (NIST) is an agency of the United States Department of Commerce whose mission is to promote American innovation and industrial competitiveness. NIST's activities are organized into physical s ...
, year=2014 , quote=
CODATA recommended value.
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Magnetism