Lawrence Berkeley National Laboratory

The independent particle approximation is shown to break down for the photoionization of both inner and outer nl \(l>0\) electrons of all atoms, at high enough energy, owing to interchannel interactions with the nearby ns photoionization channels. The effect is illustrated for Ne 2p in the 1 keV photon energy range through a comparison of theory and experiment. The implications for x-ray photoelectron spectroscopy of molecules and condensed matter are discussed.