| System of units | Value |
|---|---|
| SI | 5.0507837393(16)×10−27 J⋅T−1[1] |
| Gaussian | 5.05078374×10−24 erg·G−1[2] |
| eV | 3.15245125417(98)×10−8 eV·T−1[3] |
| MHz/T (per h) | 7.6225932188(24) MHz/T[4] |
The nuclear magneton (symbol μN) is a physical constant of magnetic moment, defined in SI units by: and in Gaussian CGS units by: where:
- e is the elementary charge,
- ħ is the reduced Planck constant,
- mp is the proton rest mass, and
- c is the speed of light
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 μN:
- μp = 2.793 μN
- μn = −1.913 μN
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 μN by a factor equal to the proton-to-electron mass ratio, about 1836.
- ^ "2022 CODATA Value: nuclear magneton". The NIST Reference on Constants, Units, and Uncertainty. NIST. May 2024. Retrieved 2024-05-18.
- ^ Since the 2019 revision of the SI, the Gauss is no longer exactly corresponds to 10−4 T.
- ^ "2022 CODATA Value: nuclear magneton in eV/T". NIST. 2022.
- ^ "2022 CODATA Value: nuclear magneton in MHz/T: μN/h". NIST. 2022.