Neutron-proton mass difference energy equivalent in MeV
Atomic & nuclearMeasured
= 1.293 332 51(38) MeV
- Value
- 1.293 332 51 MeV
- Standard uncertainty
- 3.8 × 10−7 MeV
- Relative uncertainty
- 2.9 × 10−7 (294 parts per billion)
- Status
- Measured
- Symbol
- Source
- CODATA 2022 via NIST · NIST entry
Use in a calculation
# neutron-proton mass difference energy equivalent in MeV, CODATA 2022 (NIST)
neutron_proton_mass_difference_energy_eq = 1.29333251 # MeV, standard uncertainty 3.8e-7
# SciPy: scipy.constants.physical_constants['neutron-proton mass difference energy equivalent in MeV']What it is
The neutron–proton mass difference expressed as an energy, in mega-electronvolts: the energy available, apart from recoil, when a free neutron decays.
In other units
| Unit | Value | |
|---|---|---|
| CGS (cm2 g s−2) | 2.072 147 13 × 10−6 | |
| eV electronvolt | 1 293 332.51 | |
| keV kiloelectronvolt | 1293.332 51 | |
| GeV gigaelectronvolt | 0.001 293 332 51 | |
| Eₕ hartree | 47 529.0931 | unit is itself measured |
| Ry rydberg | 95 058.1862 | unit is itself measured |
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 | 1.293 332 51(38) | 2.9 × 10−7 | +0.3 σ of 2018 |
| 2018 | 1.293 332 36(46) | 3.6 × 10−7 |
“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).