nanoelectronvolt

The nanoelectronvolt (neV) is a unit of energy equal to one billionth of an electronvolt. Since 1 eV equals 1.602176634×10^-19 joules, 1 neV equals 1.602176634×10^-28 joules. This is an extremely small energy scale used in specialized areas of physics where energies at or below microkelvin temperatures or very small quantum splittings are relevant.

Converting neV into other common quantities helps place its size. In frequency terms, E = h f, so 1 neV corresponds to f ≈ 2.42×10^5 Hz (about 240 kHz). In temperature units, E = k_B T gives T ≈ 1.16×10^-5 K (about 11 μK). For photons, the energy relation E = hc/λ implies a wavelength of roughly 1,240 meters (about 1.2 km) for a 1 neV photon.

In practice, neV-scale energies arise in ultracold physics and precision measurements, where thermal energies are suppressed to tens of microkelvin or below and energy level splittings become tiny. The neV unit is useful for expressing very small energy differences in nanoscale systems, ultracold atomic experiments, and certain condensed-matter or quantum-information contexts. It is much smaller than typical electronic energies (eV to meV) and far below everyday laboratory energies, reflecting the niche but important role of ultra-low-energy phenomena in modern physics.