Nuclear relaxation, core electron excitation

In the main, Cu Is —> 4p, and the shakedown, Cu Is 4p + LMCT, processes, excitation of a Is core electron into the 4p orbital (an electric dipole -allowed transition z-pol for Is —> 4pz) creates a core hole, which results in an increased effective nuclear charge on the Cu felt by the valence d orbitals shifting these to deeper binding energies as shown schematically in Fig. 6B, 1 —> 2. For Cu(II) complexes, the half occupied 3d v v orbital relaxes to an energy below that of the filled ligand valence orbitals. As a result of this relaxation, a lower energy... 

The efficient screening approximation means essentially that the final state of the core, containing a hole, is a completely relaxed state relative to its immediate surround-ing In the neighbourhood of the photoemission site, the conduction electron density of charge redistributes in such a way to suit the introduction of a core in which (differently from the normal ion cores of the metal) there is one hole in a deep bound state, and one valence electron more. The effect of a deep core hole (relative to the outer electrons), may be easily described as the addition of a positive nuclear charge (as, e.g. in P-radioactive decay). Therefore, the excited core can be described as an impurity in the metal. If the normal ion core has Z nuclear charges (Z atomic number) and v outer electrons (v metallic valence) the excited core is similar to an impurity having atomic number (Z + 1) and metalhc valence (v + 1) (e.g., for La ion core in lanthanum metal, the excited core is similar to a Ce impurity). 

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