Reduced tau Compton wavelength
Atomic & nuclearMeasured
= 1.110 538(75) × 10−16 m
- Value
- 1.110 538 × 10−16 m
- Standard uncertainty
- 7.5 × 10−21 m
- Relative uncertainty
- 6.8 × 10−5 (68 parts per million)
- Status
- Measured
- Symbol
- Source
- CODATA 2022 via NIST · NIST entry
Use in a calculation
# reduced tau Compton wavelength, CODATA 2022 (NIST)
reduced_tau_compton_wavelength = 1.110538e-16 # m, standard uncertainty 7.5e-21
# SciPy: scipy.constants.physical_constants['reduced tau Compton wavelength']What it is
The Compton wavelength of the tau, the heaviest of the three charged leptons, divided by 2π: ħ/(mc).
In other units
| Unit | Value | |
|---|---|---|
| CGS (cm) | 1.110 538 × 10−14 | |
| fm femtometre | 0.111 0538 |
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 | 1.110 538(75) × 10−16 | 6.8 × 10−5 | +0.0 σ of 2018 |
| 2018 | 1.110 538(75) × 10−16 | 6.8 × 10−5 | −0.2 σ of 2014 |
| 2014 | 0.111 056(10) × 10−15 | 9.0 × 10−5 | +0.0 σ of 2010 |
| 2010 | 0.111 056(10) × 10−15 | 9.0 × 10−5 | +0.6 σ of 2006 |
| 2006 | 0.111 046(18) × 10−15 | 1.6 × 10−4 | +0.0 σ of 2002 |
| 2002 | 0.111 046(18) × 10−15 | 1.6 × 10−4 | +0.2 σ of 1998 |
| 1998 | 0.111 042(18) × 10−15 | 1.6 × 10−4 |
“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).