Proton-neutron magnetic moment ratio

$μₚ/μₙ$ = −1.459 898 02(34)

Value: −1.459 898 02
Standard uncertainty: 3.4 × 10⁻⁷
Relative uncertainty: 2.3 × 10⁻⁷ (233 parts per billion)
Status: Measured
Symbol: $μₚ/μₙ$
Source: CODATA 2022 via NIST · NIST entry

Use in a calculation

# proton-neutron magnetic moment ratio, CODATA 2022 (NIST)
proton_neutron_magnetic_moment_ratio = -1.45989802  # standard uncertainty 3.4e-7

# SciPy: scipy.constants.physical_constants['proton-neutron mag. mom. ratio']

What it is

The magnetic moment of the proton divided by the magnetic moment of the neutron. Ratios like this are often measured more precisely than either quantity on its own, which is why CODATA lists them.

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	−1.459 898 02(34)	2.3 × 10⁻⁷	+0.1 σ of 2018
2018	−1.459 898 05(34)	2.3 × 10⁻⁷	+0.0 σ of 2014
2014	−1.459 898 05(34)	2.3 × 10⁻⁷	+0.0 σ of 2010
2010	−1.459 898 06(34)	2.3 × 10⁻⁷	+0.0 σ of 2006
2006	−1.459 898 06(34)	2.3 × 10⁻⁷	−0.0 σ of 2002
2002	−1.459 898 05(34)	2.3 × 10⁻⁷	+0.0 σ of 1998
1998	−1.459 898 05(34)	2.3 × 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).