4.3.1: Energy Units in Nuclear Physics


The relevant energies in nuclear physics, even the largest ones, are only tiny fractions of a Joule, the standard unit in the SI system. For instance, the products of the most energetic $$a, \beta$$ and $$\gamma$$ decays carry energies of the order of $$10^{-13} \mathrm{~J}$$. The record-high energies, those observed in fission reactions, are still of the order of one hundredth of one billionth $$\left(10^{-11}\right)$$ of one Joule. Working with such small numbers is certainly not too convenient. Therefore, nuclear physicists created a more "user-friendly" energy unit, the electronVolt, with a symbol "eV". By definition, it is the amount of energy gained (or lost) by the charge of a single electron moving across an electric potential difference of one volt: $$1 \mathrm{eV}=1.602^{*} 10^{-19}$$.

Practical units based on the electron-Volt are: the kilo-electron-Volt, 1 $$\mathrm{keV}=$$ one thousand eV; the mega-electron-Volt, $$1 \mathrm{MeV}=$$ one million $$\mathrm{eV}$$; as well as the milli-electronvolt, $$1 \mathrm{meV}=$$ one thousandth of $$1 \mathrm{eV}$$, and the micro-electron-Volt, $$1 \mu \mathrm{eV}=$$ one millionth of $$1 \mathrm{eV}$$.

4.3.1: Energy Units in Nuclear Physics is shared under a CC BY 1.3 license and was authored, remixed, and/or curated by Tom Giebultowicz.