Shielded proton magnetic moment

$μ_{p^{'}}$ = 1.410 570 5830(58) × 10⁻²⁶ J T⁻¹

Value: 1.410 570 5830 × 10⁻²⁶ J T⁻¹
Standard uncertainty: 5.8 × 10⁻³⁵ J T⁻¹
Relative uncertainty: 4.1 × 10⁻⁹ (4.1 parts per billion)
Status: Measured
Symbol: $μ_{p^{'}}$
Source: CODATA 2022 via NIST · NIST entry

Use in a calculation

# shielded proton magnetic moment, CODATA 2022 (NIST)
shielded_proton_magnetic_moment = 1.410570583e-26  # J T^-1, standard uncertainty 5.8e-35

# SciPy: scipy.constants.physical_constants['shielded proton mag. mom.']

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: how strongly it behaves like a tiny bar magnet. A negative value means it 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).

Relative uncertainty

CODATA	Value (uncertainty)	Relative uncertainty	Change from previous
2022	1.410 570 5830(58) × 10⁻²⁶	4.1 × 10⁻⁹	+1.5 σ of 2018
2018	1.410 570 560(15) × 10⁻²⁶	1.1 × 10⁻⁸	+0.7 σ of 2014
2014	1.410 570 547(18) × 10⁻²⁶	1.3 × 10⁻⁸	+1.4 σ of 2010
2010	1.410 570 499(35) × 10⁻²⁶	2.5 × 10⁻⁸	+2.1 σ of 2006
2006	1.410 570 419(38) × 10⁻²⁶	2.7 × 10⁻⁸	−0.4 σ of 2002
2002	1.410 570 47(12) × 10⁻²⁶	8.5 × 10⁻⁸	+1.2 σ of 1998
1998	1.410 570 399(59) × 10⁻²⁶	4.2 × 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).