Resonant photoemission vs. Coster-Kronig Auger decay at the LIII thresholds of Ni metal and CuO

We report on a resonant photoemission study of Ni metal and CuO at the LIII soft-X-ray absorption thresholds. The valence band spectra exhibit a strong enhancement of electron emission at resonance, which is shown to be mostly due to an incoherent superposition of a photoemission signal with a more intense signal from L3M4,5M4,5 Coster-Kronig decay of the core-ionized state. The resonant enhancement of the valence band photoemission satellite amounts to a factor of ≅ 12, far short of the recent claim of a giant resonance. Implications of these results with respect to the nature of the 3d states in these materials are briefly discussed