Electron to shielded helion magnetic moment ratio

$μₑ/μₕ′$ = 864.058 239 86(70)

Value: 864.058 239 86
Standard uncertainty: 7 × 10⁻⁷
Relative uncertainty: 8.1 × 10⁻¹⁰ (810 parts per trillion)
Status: Measured
Symbol: $μₑ/μₕ′$
Source: CODATA 2022 via NIST · NIST entry

Use in a calculation

# electron to shielded helion magnetic moment ratio, CODATA 2022 (NIST)
electron_to_shielded_helion_magnetic_mom = 8.6405823986e2  # standard uncertainty 7e-7

# SciPy: scipy.constants.physical_constants['electron to shielded helion mag. mom. ratio']

What it is

The magnetic moment of the electron divided by the magnetic moment of the shielded helion. 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	864.058 239 86(70)	8.1 × 10⁻¹⁰	−1.7 σ of 2018
2018	864.058 257(10)	1.2 × 10⁻⁸	+0.0 σ of 2014
2014	864.058 257(10)	1.2 × 10⁻⁸	+0.0 σ of 2010
2010	864.058 257(10)	1.2 × 10⁻⁸	+0.0 σ of 2006
2006	864.058 257(10)	1.2 × 10⁻⁸	+0.2 σ of 2002
2002	864.058 255(10)	1.2 × 10⁻⁸	+0.0 σ of 1998
1998	864.058 255(10)	1.2 × 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).