The story
Named after Oskar Klein and Yoshio Nishina who derived the equation in 1928.
Etymology from Wiktionary, CC BY-SA 4.0.
Klein-Nishina formula
Today it means: A formula for the differential cross section of photons scattered from a single free electron, calculated in the lowest order of quantum electrodynamics: (dσ)/(dΩ)=1/2r_e²(λ/(λ'))²[λ/(λ')+(λ')/λ- sin ²(θ)], where r_e is the classical electron radius, λ/λ' is the ratio of the wavelengths of the incident and scattered photons, and θ is the scattering angle (0 for an undeflected photon). Full definition →