Shielded helion gyromagnetic ratio

$γ_{h^{'}}$ = 2.037 894 6078(18) × 10⁸ s⁻¹ T⁻¹

Value: 2.037 894 6078 × 10⁸ s⁻¹ T⁻¹
Standard uncertainty: 0.18 s⁻¹ T⁻¹
Relative uncertainty: 8.8 × 10⁻¹⁰ (883 parts per trillion)
Status: Measured
Symbol: $γ_{h^{'}}$
Source: CODATA 2022 via NIST · NIST entry

Use in a calculation

# shielded helion gyromagnetic ratio, CODATA 2022 (NIST)
shielded_helion_gyromagnetic_ratio = 2.0378946078e8  # s^-1 T^-1, standard uncertainty 0.18

# SciPy: scipy.constants.physical_constants['shielded helion gyromag. ratio']

What it is

The ratio of magnetic moment to angular momentum for a helion in a helium-3 gas atom (spherical sample at 25 °C), screened by the atom's two electrons. In a magnetic field B the spin precesses at angular frequency γB; this is the basis of magnetic resonance.

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	2.037 894 6078(18) × 10⁸	8.8 × 10⁻¹⁰	+1.6 σ of 2018
2018	2.037 894 569(24) × 10⁸	1.2 × 10⁻⁸	−0.6 σ of 2014
2014	2.037 894 585(27) × 10⁸	1.3 × 10⁻⁸	−1.5 σ of 2010
2010	2.037 894 659(51) × 10⁸	2.5 × 10⁻⁸	−1.3 σ of 2006
2006	2.037 894 730(56) × 10⁸	2.7 × 10⁻⁸	+0.2 σ of 2002
2002	2.037 894 70(18) × 10⁸	8.8 × 10⁻⁸	−0.8 σ of 1998
1998	2.037 894 764(85) × 10⁸	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).