Resonant photoemission at the 3p-core threshold from quasiatomic Ni in nickel-phthalocyanine

In nickel-phthalocyanine a resonant enhancement at the 3p?Ni photo-absorption maximum ($\text{hv ? 68.5 eV}$) of a peak approximately 6 eV below the maximum of the Ni 3d derived states is observed in photoemission experiments with variable excitation energy (synchrotron radiation). Our observation of this resonance, explained by configuration interaction of Ni 3p→3d and 3d-continuum transitions, gives direct evidence for the atomic nature of the 6 eV resonance structure in photoemission from bulk Ni.