Line Narrowing in Photoemission by Coincidence Spectroscopy

We present photoemission spectra from the 3p level of Cu (100) obtained in coincidence with the M₃VV Auger line. The 3p level is narrowed from its 2. 2-eV core-lifetime-broadened width to 1. 0 eV, representing the intrinsic width of the ^1G Auger final state. The core line changes its energy within the 2. 2-eV envelope as the Auger coincidence energy is changed, conserving the sum of Auger-electron and photoelectron kinetic energies.