megaelectronvolts

Megaelectronvolt (MeV) is a unit of energy commonly used in atomic, nuclear, and particle physics. It equals one million electronvolts, with the symbol MeV. The electronvolt is the energy gained by an elementary charge moving through one volt, making MeV a convenient energy scale for subatomic particles. In particle physics, energies are frequently stated in MeV, while masses are often given in MeV/c^2.

One electronvolt is exactly 1.602176634×10−19 joule, so 1 MeV = 10^6 eV = 1.602176634×10−13 J.

This scale covers particle rest energies, nuclear binding energies, and reaction thresholds. For example, the rest energy of the electron is about 0.511 MeV, while the proton and neutron rest energies are about 938 MeV and 939 MeV, respectively. Nuclear binding energies average around 8 MeV per nucleon.

MeV are used to describe energy releases in nuclear transitions, radiative processes, and the energy of particles produced in accelerators and cosmic sources. In practical applications, MeV-level photons and electrons are common in medical radiotherapy; high-energy accelerators generate photons and electrons in the several MeV range, while gamma rays from some nuclear decays reach into the MeV scale.

The megavolt prefix is part of the same set of SI-derived prefixes as keV and GeV, and the MeV unit is widely used in contexts alongside other energy scales. In particle physics, masses are often quoted in MeV/c^2.