Two-electron resonance at the 3p threshold of Cu and Ni

A sharp 3d-electron satellite excitation has been found for Cu which exhibits a strong resonant enhancement (× 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 two 3d holes plus one 4s electron (3d84s). Present models for the Ni resonant satellite are not able to describe our Cu results. © 1979 The American Physical Society.