Crystal momentum dependence of the correlation satellite intensity in the 3p-3d resonant photoemission spectra of Bi2Sr2CaCu2O8+

Angle-resolved resonant photoemission measurements at the Cu3p -> Cu3d threshold have been performed on the superconducting cuprate Bi2Sr2CaCu2O8+?. We have investigated in particular the correlation satellite appearing in the valence band photoemission spectrum to investigate the effect of solid state on the interference effect occurring at resonance. We found that the intensity of the correlation satellite changes with the electron take-off angle in a way that depends on the particular crystallographic direction and on the sample hole doping. These results indicate that the intensity enhancement at the absorption edge is a real resonance albeit the intermediate state in the autoionization process is partly delocalised. This fact does not prevent the occurrence of interference between indirect and direct photoemission.