Helion shielding shift

$σ_{h}^{'}$ = 5.996 7029(23) × 10⁻⁵

Value: 5.996 7029 × 10⁻⁵
Standard uncertainty: 2.3 × 10⁻¹¹
Relative uncertainty: 3.8 × 10⁻⁷ (384 parts per billion)
Status: Measured
Symbol: $σ_{h}^{'}$
Source: CODATA 2022 via NIST · NIST entry

Use in a calculation

# helion shielding shift, CODATA 2022 (NIST)
helion_shielding_shift = 5.9967029e-5  # standard uncertainty 2.3e-11

# SciPy: scipy.constants.physical_constants['helion shielding shift']

What it is

The fraction by which the two electrons of a helium-3 atom reduce the magnetic field felt by its nucleus. It links the magnetic moment of the bare helion to the shielded value that experiments measure.

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	5.996 7029(23) × 10⁻⁵	3.8 × 10⁻⁷	−4.0 σ of 2018
2018	5.996 743(10) × 10⁻⁵	1.7 × 10⁻⁶

“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).