ConstantID

Proton g factor

Atomic & nuclearMeasured

gp = 5.585 694 6893(16)

Value
5.585 694 6893
Standard uncertainty
1.6 × 10−9
Relative uncertainty
2.9 × 10−10 (286 parts per trillion)
Status
Measured
Symbol
gp
Source
CODATA 2022 via NIST · NIST entry

Use in a calculation

# proton g factor, CODATA 2022 (NIST)
proton_g_factor = 5.5856946893  # standard uncertainty 1.6e-9

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

What it is

The g-factor of the proton, the nucleus of the hydrogen atom: 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).

proton g factor: CODATA values 1998–2022 relative to the 2022 value, in parts per billion, with one-standard-uncertainty bars−6−4−20+2+4+6parts per billion1998200220062010201420182022

Relative uncertainty

proton g factor: relative standard uncertainty in each CODATA adjustment, logarithmic scale10⁻¹⁰10⁻⁹10⁻⁸10⁻⁷1998200220062010201420182022
CODATAValue (uncertainty)Relative uncertaintyChange from previous
20225.585 694 6893(16)2.9 × 10−10 +0.0 σ of 2018
20185.585 694 6893(16)2.9 × 10−10 −0.7 σ of 2014
20145.585 694 702(17)3.0 × 10−9 −0.2 σ of 2010
20105.585 694 713(46)8.2 × 10−9 +0.0 σ of 2006
20065.585 694 713(46)8.2 × 10−9 +0.2 σ of 2002
20025.585 694 701(56)1.0 × 10−8 +0.5 σ of 1998
19985.585 694 675(57)1.0 × 10−8

“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 e/mp Proton charge to mass quotient 9.578 833 1430(30) × 107 C kg−1 Atomic & nuclear λC,p Proton Compton wavelength 1.321 409 853 60(41) × 10−15 m Atomic & nuclear mp/me Proton–electron mass ratio 1836.152 673 426(32) Atomic & nuclear γp Proton gyromagnetic ratio 2.675 221 8708(11) × 108 s−1 T−1 Atomic & nuclear γp/2π Proton gyromagnetic ratio in MHz/T 42.577 478 461(18) MHz T−1 Atomic & nuclear μp Proton magnetic moment 1.410 606 795 45(60) × 10−26 J T−1 Atomic & nuclear μp/μB Proton magnetic moment to Bohr magneton ratio 1.521 032 202 30(45) × 10−3 Atomic & nuclear μp/μN Proton magnetic moment to nuclear magneton ratio 2.792 847 344 63(82)