Reduced proton Compton wavelength

$λ̄_C,p$ = 2.103 089 100 51(66) × 10⁻¹⁶ m

Value: 2.103 089 100 51 × 10⁻¹⁶ m
Standard uncertainty: 6.6 × 10⁻²⁶ m
Relative uncertainty: 3.1 × 10⁻¹⁰ (314 parts per trillion)
Status: Measured
Symbol: $λ̄_C,p$
Source: CODATA 2022 via NIST · NIST entry

Use in a calculation

# reduced proton Compton wavelength, CODATA 2022 (NIST)
reduced_proton_compton_wavelength = 2.10308910051e-16  # m, standard uncertainty 6.6e-26

# SciPy: scipy.constants.physical_constants['reduced proton Compton wavelength']

What it is

The Compton wavelength of the proton, the nucleus of the hydrogen atom, divided by 2π: ħ/(mc).

In other units

Unit	Value
CGS (cm)	2.103 089 100 51 × 10⁻¹⁴
fm femtometre	0.210 308 910 051

Converted with ConstantID's unit table; digits are rounded to the precision of the value, and a long exact value is rounded only for display. The relative uncertainty is unchanged by conversion to an exactly defined unit.

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	2.103 089 100 51(66) × 10⁻¹⁶	3.1 × 10⁻¹⁰	−4.5 σ of 2018
2018	2.103 089 103 36(64) × 10⁻¹⁶	3.0 × 10⁻¹⁰	+2.3 σ of 2014
2014	0.210 308 910 109(97) × 10⁻¹⁵	4.6 × 10⁻¹⁰	−2.4 σ of 2010
2010	0.210 308 910 47(15) × 10⁻¹⁵	7.1 × 10⁻¹⁰	+6.2 σ of 2006
2006	0.210 308 908 61(30) × 10⁻¹⁵	1.4 × 10⁻⁹	−1.3 σ of 2002
2002	0.210 308 9104(14) × 10⁻¹⁵	6.7 × 10⁻⁹	+0.9 σ of 1998
1998	0.210 308 9089(16) × 10⁻¹⁵	7.6 × 10⁻⁹

“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).