Ni L-Edge Absorption Structure of K₂Ni(CN)₄ Ionic Solid Investigated with Resonant Photoelectron Spectroscopy

Abstract
Resonant photoelectron spectra of the K₂Ni(CN)₄ ionic solid following the Ni 2p photoabsorption were measured to interpret the I^edge absorption spectrum. [Ni₂CN₄]^2- is a square-planar complex ion and its absorption spectrum shows rather complicated resonance features in comparison with those of nickel oxide and nickel dihalides. In the resonant photoelectron spectra, all the peaks enhanced by resonant photoabsorption have higher kinetic energies than the normal Auger peaks and are attributable to spectator Auger transitions. It is clearly observed that the kinetic energies of all the spectator Auger electrons decrease with increase of the photon energy in the Ni 2p_3/2 photoexcited region. The kinetic energy dependence observed is reasonable assuming that the Ni L-edee resonance absorptions are exciton-like and excited electrons are shaken up with high probability.