Resonant Inverse Photoemission and Many-Body Effect in Nickel

Abstract

We calculate a resonant inverse photoemission spectroscopy (IPES) spectrumat the Ni 3p core threshold (3dⁿ → 3p⁵3dⁿ⁺² → 3dⁿ⁺¹), from a viewpoint of a many-bodyconfiguration interaction (CI), on the basis of the Anderson impurity model. The calculated IPES spectrum exhibits a single main peak just above theFermi level E_F under off-resonance, while it has a shoulder extending to 4 eV aboveE_F under on-resonance conditions. Under on-resonance conditions, the main peak intensity shows a dip whosemagnitude is a function of the incident electron energy ε, while the shoulder isresonantly enhanced. The interference between the direct 3d⁸ → 3d⁹ and resonant 3d⁸ → 3p⁵3d¹⁰ → 3d⁹ processesand CI in both the initial and final states leads to the above result.Resonant IPES is therefore considered to be a promising method of directlydetermining whether a 3d⁸ configuration in the initial state, inferred by analysis of various high-energy spectroscopic data, does in fact exist.The main peak is assigned to the bonding state of 3d¹⁰ and 3d⁹configurations and the shoulder a non-bonding and the anti-bonding states of them.