Shielded proton magnetic moment to nuclear magneton ratio

$μₚ′/μ_N$ = 2.792 775 648(11)

Value: 2.792 775 648
Standard uncertainty: 1.1 × 10⁻⁸
Relative uncertainty: 3.9 × 10⁻⁹ (3.9 parts per billion)
Status: Measured
Symbol: $μₚ′/μ_N$
Source: CODATA 2022 via NIST · NIST entry

Use in a calculation

# shielded proton magnetic moment to nuclear magneton ratio, CODATA 2022 (NIST)
shielded_proton_magnetic_moment_to_nucle = 2.792775648  # standard uncertainty 1.1e-8

# SciPy: scipy.constants.physical_constants['shielded proton mag. mom. to nuclear magneton ratio']

What it is

The magnetic moment of a proton in a spherical sample of pure water at 25 °C, whose magnetic field is partly screened by the surrounding electrons, expressed in nuclear magnetons.

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).

Relative uncertainty

CODATA	Value (uncertainty)	Relative uncertainty	Change from previous
2022	2.792 775 648(11)	3.9 × 10⁻⁹	+1.6 σ of 2018
2018	2.792 775 599(30)	1.1 × 10⁻⁸	−0.0 σ of 2014
2014	2.792 775 600(30)	1.1 × 10⁻⁸	+0.1 σ of 2010
2010	2.792 775 598(30)	1.1 × 10⁻⁸	+0.0 σ of 2006
2006	2.792 775 598(30)	1.1 × 10⁻⁸	−0.2 σ of 2002
2002	2.792 775 604(30)	1.1 × 10⁻⁸	+0.2 σ of 1998
1998	2.792 775 597(31)	1.1 × 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).