Shielded proton magnetic moment to Bohr magneton ratio

$μₚ′/μ_B$ = 1.520 993 1551(62) × 10⁻³

Value: 1.520 993 1551 × 10⁻³
Standard uncertainty: 6.2 × 10⁻¹²
Relative uncertainty: 4.1 × 10⁻⁹ (4.1 parts per billion)
Status: Measured
Symbol: $μₚ′/μ_B$
Source: CODATA 2022 via NIST · NIST entry

Use in a calculation

# shielded proton magnetic moment to Bohr magneton ratio, CODATA 2022 (NIST)
shielded_proton_magnetic_moment_to_bohr_ = 1.5209931551e-3  # standard uncertainty 6.2e-12

# SciPy: scipy.constants.physical_constants['shielded proton mag. mom. to Bohr 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 Bohr 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	1.520 993 1551(62) × 10⁻³	4.1 × 10⁻⁹	+1.6 σ of 2018
2018	1.520 993 128(17) × 10⁻³	1.1 × 10⁻⁸	+0.0 σ of 2014
2014	1.520 993 128(17) × 10⁻³	1.1 × 10⁻⁸	+0.0 σ of 2010
2010	1.520 993 128(17) × 10⁻³	1.1 × 10⁻⁸	+0.0 σ of 2006
2006	1.520 993 128(17) × 10⁻³	1.1 × 10⁻⁸	−0.2 σ of 2002
2002	1.520 993 132(16) × 10⁻³	1.1 × 10⁻⁸	+0.0 σ of 1998
1998	1.520 993 132(16) × 10⁻³	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).