Shake-down satellites

In light lanthanides (La, Ce, Pr, Nd) the pulled down 4f state is nearly localized and hybridizes only weakly with conduction states. The bandwidth W4f will be very narrow, U high and negative, and the occupation probabiUty by conduction electrons rather low. This results in the occurrence of shake-down satellites at a lower binding energy for lanthanides, accompanying a poorly screened main peak (Fig. 7 a). When proceeding to heavier lanthanides, the occupation probability and the intensity of the shake-down satellite are depressed the symmetric, poorly screened core level is left, i.e. the 4f states are completely localized. 

Fig. 9.13. XPE spectra of 3d3/2 region of Nd203 showing the existence of shake-down charge transfer satellite peak on the lower binding energy side of the main peak [50].

The observed shakedown is analogous to the satellites observed in photoelectron spectroscopy and can be treated in a similar manner [25]. This analysis enables us to quantify the intensity of the Is —> 4p + LMCT shakedown feature as a percentage of the total Is > 4p transition intensity. Comparison of the shakedown intensity to that of the Is > 3d(+4p) pre-edge transition (at 8,979 eV) then allows for quantitation of the amount of 4pz mixing into the 3d orbital. Within the sudden approximation [28-30], the creation of the core hole occurs rapidly, before the electron adjusts to the new potential. Here, the intensity /j of a given transition corresponding to either the main (Is —> 4p ) or shake down (Is —> 4p + LMCT) final state can then be given by the Sudden approximation... 

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