Resonance photoemission at the 2p excitation threshold of Ni{001}

Resonance enhancement of the 3d photoemission intensity in angle-integrated electron-distribution curves from Ni{001} is observed when the photon energy is varied in the vicinity of the Ni 2p absorption threshold. Explanation of the effect involves a Fano-like interference between continuum excitation from the 3d band and discrete excitation from the 2p level to form a core exciton, coupled to each other via the decay of the exciton and the ejection of a 3d electron into the continuum. The binding energy of the core exciton is about 3.5 eV below the absorption threshold. Differences between the 2p 3d and the well-known 3p 3d resonance effect are discussed.