Two-Electron Resonance at the $3 p$ Threshold of $Cu$ and $Ni$

A sharp 3d-electron satellite excitation has been found for Cu which exhibits a strorg resonant enhancement (x 5) at the Cu 3p-core-level threshold similar to the 6-eV resonant satellite observed previously in Ni. This satellite, which has two peaks at 11.8 and 14.6 eV below EF, is identified as a quasiatomic two-electron excitation with bvo 3d holes plus one 4s electron (3d 4s). Present models for the 1iresonant satellite are not able to describe our Cu results.