ConstantID

Neutron g factor

Atomic & nuclearMeasured

gn = −3.826 085 52(90)

Value
−3.826 085 52
Standard uncertainty
9 × 10−7
Relative uncertainty
2.4 × 10−7 (235 parts per billion)
Status
Measured
Symbol
gn
Source
CODATA 2022 via NIST · NIST entry

Use in a calculation

# neutron g factor, CODATA 2022 (NIST)
neutron_g_factor = -3.82608552  # standard uncertainty 9e-7

# SciPy: scipy.constants.physical_constants['neutron g factor']

What it is

The g-factor of the neutron, the electrically neutral nucleon: the pure number that relates its magnetic moment to its spin angular momentum. A negative value means the moment points opposite to the spin.

How the value changed, 1998–2022

Each point is one CODATA adjustment, plotted as its difference from the 2022 value; the bars show one standard uncertainty (an arrowhead means the bar runs off the chart).

neutron g factor: CODATA values 1998–2022 relative to the 2022 value, in parts per billion, with one-standard-uncertainty bars−600−400−2000+200+400+600parts per billion1998200220062010201420182022

Relative uncertainty

neutron g factor: relative standard uncertainty in each CODATA adjustment, logarithmic scale10⁻⁸10⁻⁷10⁻⁶1998200220062010201420182022
CODATAValue (uncertainty)Relative uncertaintyChange from previous
2022−3.826 085 52(90)2.4 × 10−7 −0.1 σ of 2018
2018−3.826 085 45(90)2.4 × 10−7 +0.0 σ of 2014
2014−3.826 085 45(90)2.4 × 10−7 +0.0 σ of 2010
2010−3.826 085 45(90)2.4 × 10−7 +0.0 σ of 2006
2006−3.826 085 45(90)2.4 × 10−7 +0.0 σ of 2002
2002−3.826 085 46(90)2.4 × 10−7 −0.0 σ of 1998
1998−3.826 085 45(90)2.4 × 10−7

“Change from previous” is the shift in the value divided by the standard uncertainty of the previous adjustment. Earlier values are converted into the current unit where NIST changed it (for example J s to J Hz⁻¹).

Related constants

Atomic & nuclear λC,n Neutron Compton wavelength 1.319 590 903 82(67) × 10−15 m Atomic & nuclear μn/μe Neutron-electron magnetic moment ratio 1.040 668 84(24) × 10−3 Atomic & nuclear mn/me Neutron-electron mass ratio 1838.683 662 00(74) Atomic & nuclear γn Neutron gyromagnetic ratio 1.832 471 74(43) × 108 s−1 T−1 Atomic & nuclear γn/2π Neutron gyromagnetic ratio in MHz/T 29.164 6935(69) MHz T−1 Atomic & nuclear μn Neutron magnetic moment −9.662 3653(23) × 10−27 J T−1 Atomic & nuclear μn/μB Neutron magnetic moment to Bohr magneton ratio −1.041 875 65(25) × 10−3 Atomic & nuclear μn/μN Neutron magnetic moment to nuclear magneton ratio −1.913 042 76(45)