Reduced muon Compton wavelength

$λ̄_C,μ$ = 1.867 594 306(42) × 10⁻¹⁵ m

Value: 1.867 594 306 × 10⁻¹⁵ m
Standard uncertainty: 4.2 × 10⁻²³ m
Relative uncertainty: 2.2 × 10⁻⁸ (22 parts per billion)
Status: Measured
Symbol: $λ̄_C,μ$
Source: CODATA 2022 via NIST · NIST entry

Use in a calculation

# reduced muon Compton wavelength, CODATA 2022 (NIST)
reduced_muon_compton_wavelength = 1.867594306e-15  # m, standard uncertainty 4.2e-23

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

What it is

The Compton wavelength of the muon, an unstable heavier cousin of the electron (about 207 times its mass) that lives about 2.2 microseconds, divided by 2π: ħ/(mc).

In other units

Unit	Value
CGS (cm)	1.867 594 306 × 10⁻¹³
pm picometre	0.001 867 594 306
fm femtometre	1.867 594 306

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	1.867 594 306(42) × 10⁻¹⁵	2.2 × 10⁻⁸	+0.0 σ of 2018
2018	1.867 594 306(42) × 10⁻¹⁵	2.2 × 10⁻⁸	−0.0 σ of 2014
2014	1.867 594 308(42) × 10⁻¹⁵	2.2 × 10⁻⁸	+0.3 σ of 2010
2010	1.867 594 294(47) × 10⁻¹⁵	2.5 × 10⁻⁸	−0.0 σ of 2006
2006	1.867 594 295(47) × 10⁻¹⁵	2.5 × 10⁻⁸	−0.1 σ of 2002
2002	1.867 594 298(47) × 10⁻¹⁵	2.5 × 10⁻⁸	−2.7 σ of 1998
1998	1.867 594 444(55) × 10⁻¹⁵	2.9 × 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).