Sub-electron volt resolutions and surface termination maps may be acquired by the application of an energy filter in a technique based on this phenomenon which is named in analogy to LEED and LEEM. The readouts for a technique based on this phenomenon may be expressed as the product of the dipole selection rules and the spectral function. A family of techniques that utilize this phenomenon include hemispherical analyzers in their setups that allow for the mapping (15[1])of (*) Fermi surfaces. A technique based on this phenomenon developed by Kai Siegbahn irradiates a material with a beam of X-rays to obtain population spectra. Energies of electrons emitted via this phenomenon must be subtracted from a material’s work function to measure (-5[1])electronic (10[1])states. (10[1])For 10 points, name this effect in which electrons are ejected from a material when hit with incident light. ■END■ (10[1])