Quantum of circulation times 2
Atomic & nuclearMeasured
= 7.273 895 0934(23) × 10−4 m2 s−1
- Value
- 7.273 895 0934 × 10−4 m2 s−1
- Standard uncertainty
- 2.3 × 10−13 m2 s−1
- Relative uncertainty
- 3.2 × 10−10 (316 parts per trillion)
- Status
- Measured
- Symbol
- Source
- CODATA 2022 via NIST · NIST entry
Use in a calculation
# quantum of circulation times 2, CODATA 2022 (NIST)
quantum_of_circulation_times_2 = 7.2738950934e-4 # m^2 s^-1, standard uncertainty 2.3e-13
# SciPy: scipy.constants.physical_constants['quantum of circulation times 2']What it is
h/mₑ, twice the quantum of circulation. Atom-interferometry measurements of h/m for atoms are one of the routes to the fine-structure constant.
In other units
| Unit | Value | |
|---|---|---|
| CGS (cm2 s−1) | 7.273 895 0934 |
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 | 7.273 895 0934(23) × 10−4 | 3.2 × 10−10 | −4.5 σ of 2018 |
| 2018 | 7.273 895 1032(22) × 10−4 | 3.0 × 10−10 | +1.8 σ of 2014 |
| 2014 | 7.273 895 0972(33) × 10−4 | 4.5 × 10−10 | −1.4 σ of 2010 |
| 2010 | 7.273 895 1040(47) × 10−4 | 6.5 × 10−10 | +6.4 σ of 2006 |
| 2006 | 7.273 895 040(10) × 10−4 | 1.4 × 10−9 | −1.3 σ of 2002 |
| 2002 | 7.273 895 101(48) × 10−4 | 6.6 × 10−9 | +1.3 σ of 1998 |
| 1998 | 7.273 895 032(53) × 10−4 | 7.3 × 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).