keV

KeV stands for kiloelectronvolt, a unit of energy commonly used in physics to describe energies of subatomic particles and photons. It equals 1,000 electronvolts; 1 eV is defined as 1.602176634×10^-19 joules, so 1 keV equals 1.602176634×10^-16 joules. A useful relation is that a 1 keV photon has a wavelength of about 1.24 nanometers, illustrating the link between energy and light frequency.

KeV is widely used to quantify photon energies in the X-ray and gamma-ray regimes, as well as kinetic energies in electron spectroscopy and inner-shell binding energies in atoms (especially for heavier elements, where shells lie in the keV range). In practice, X-ray energies from roughly 0.1 keV to tens of keV are common in instrumentation, with hard X-rays reaching into tens or hundreds of keV and gamma rays lying above that range. Prominent spectral features include the iron K-alpha line at approximately 6.4 keV.

Detector technology in X-ray and gamma-ray astronomy and spectroscopy often reports energy measurements in keV or eV, with calibration against known emission lines. KeV-scale energies also appear in theoretical physics and cosmology, where keV-mass particles, such as certain sterile neutrino models, are considered as warm dark matter candidates.

In summary, the keV unit provides a practical scale for describing moderate to high-energy phenomena in atomic, nuclear, astronomical, and particle physics.