  We have re-examined the valence-band (VB) and core-level electronic structure
of NiO by means of hard and soft x-ray photoemission spectroscopy (PES). The
spectral weight of the lowest energy state found to be enhanced in the bulk
sensitive Ni 2p core-level PES. A configuration-interaction model including the
bound state screening has shown significant agreement with the core-level
spectra, and the off and on-resonance VB spectra. These results identify the
lowest energy state in core-level and VB-PES as the Zhang-Rice doublet bound
state, consistent with the spin-fermion model and recent ab initio calculation
with dynamical mean-field theory (LDA + DMFT).
