Helion mass energy equivalent
Atomic & nuclearMeasured
= 4.499 539 4185(14) × 10−10 J
- Value
- 4.499 539 4185 × 10−10 J
- Standard uncertainty
- 1.4 × 10−19 J
- Relative uncertainty
- 3.1 × 10−10 (311 parts per trillion)
- Status
- Measured
- Symbol
- Source
- CODATA 2022 via NIST · NIST entry
Use in a calculation
# helion mass energy equivalent, CODATA 2022 (NIST)
helion_mass_energy_equivalent = 4.4995394185e-10 # J, standard uncertainty 1.4e-19
# SciPy: scipy.constants.physical_constants['helion mass energy equivalent']What it is
The rest energy (mass × c²) of the helion, the nucleus of helium-3 (two protons and one neutron), in joules.
In other units
| Unit | Value | |
|---|---|---|
| CGS (cm2 g s−2) | 0.004 499 539 4185 | |
| keV kiloelectronvolt | 2 808 391.6111 | |
| MeV megaelectronvolt | 2808.391 6111 | |
| GeV gigaelectronvolt | 2.808 391 6111 | |
| erg erg | 0.004 499 539 4185 |
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 | 4.499 539 4185(14) × 10−10 | 3.1 × 10−10 | +4.3 σ of 2018 |
| 2018 | 4.499 539 4125(14) × 10−10 | 3.1 × 10−10 | +1.3 σ of 2014 |
| 2014 | 4.499 539 341(55) × 10−10 | 1.2 × 10−8 | +1.6 σ of 2010 |
| 2010 | 4.499 539 02(20) × 10−10 | 4.4 × 10−8 | +1.7 σ of 2006 |
| 2006 | 4.499 538 64(22) × 10−10 | 4.9 × 10−8 | −0.3 σ of 2002 |
| 2002 | 4.499 538 84(77) × 10−10 | 1.7 × 10−7 | +1.0 σ of 1998 |
| 1998 | 4.499 538 48(35) × 10−10 | 7.8 × 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).