Shielded proton gyromagnetic ratio

$γ_{p^{'}}$ = 2.675 153 194(11) × 10⁸ s⁻¹ T⁻¹

Value: 2.675 153 194 × 10⁸ s⁻¹ T⁻¹
Standard uncertainty: 1.1 s⁻¹ T⁻¹
Relative uncertainty: 4.1 × 10⁻⁹ (4.1 parts per billion)
Status: Measured
Symbol: $γ_{p^{'}}$
Source: CODATA 2022 via NIST · NIST entry

Use in a calculation

# shielded proton gyromagnetic ratio, CODATA 2022 (NIST)
shielded_proton_gyromagnetic_ratio = 2.675153194e8  # s^-1 T^-1, standard uncertainty 1.1

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

What it is

The ratio of magnetic moment to angular momentum for a proton in a spherical sample of pure water at 25 °C, whose magnetic field is partly screened by the surrounding 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	2.675 153 194(11) × 10⁸	4.1 × 10⁻⁹	+1.5 σ of 2018
2018	2.675 153 151(29) × 10⁸	1.1 × 10⁻⁸	−0.6 σ of 2014
2014	2.675 153 171(33) × 10⁸	1.2 × 10⁻⁸	−1.5 σ of 2010
2010	2.675 153 268(66) × 10⁸	2.5 × 10⁻⁸	−1.3 σ of 2006
2006	2.675 153 362(73) × 10⁸	2.7 × 10⁻⁸	+0.1 σ of 2002
2002	2.675 153 33(23) × 10⁸	8.6 × 10⁻⁸	−0.7 σ of 1998
1998	2.675 153 41(11) × 10⁸	4.1 × 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).