Gunnarsson-Schonhammer

The results show that is the same for a-Ce and y-Ce and hence that changes in the n are directly related to changes in Values of the 4f-occupation (Allen et al. 1983) derived from BIS experiments on the basis of the Gunnarsson-Schonhammer (1983) (G-S) model are 1.0 for y-Ce and 0.85 for a-Ce. In our case, n is derived in a simple way by finding the minimum of the total energy curve and is different from the 4f-occupation number in the G-S model, which is the eigenvalue of a number operator in their model Hamiltonian. Since our basic quantities are total energies, a direct comparison of our results with the experimental spectra is more appropriate than is a comparison with the G-S values. 

Wuilloud et al. (1985) reported XPS and BIS measurements of CeSij which showed a peak at the Fermi level that they assigned to Ce 4f emission. They argued that these states did not overlap significantly with the Si-derived valence band states in the spectrum. These authors used the Gunnarsson-Schonhammer model to fit their BIS and XPS spectrum, adjusting the location of the bare 4f state in the elliptical valence band. 

Fig. 32. High-resolution EDC of CeCu near the Fermi energy, (a) experimental spectrum measured with a resolution of 20meV. (b) Simulation of the spectrum using the Gunnarsson-Schonhammer model with spin-orbit splitting and a constant background (dashed) of valence states. The inset shows the Fermi edge measured with a resolution of 12meV. (After Patthey et al. 1986b.)...

In the spirit of the Kotani/Toyozawa/Gunnarsson/Schonhammer approach, which was shown to work well for the calculation of the core levels of La203, the core level spectra of CeOj have been calculated (Jo and Kotani 1985 see also Schneider et al. 1985, Fujimori 1985). Figure 9 shows the calculated spectrum for one of the 3d3/2,s/2 doublets and the inset gives a measured spectrum (Kotani and Jo 1986). The calculation clearly reproduces the three final states which can be read off the diagram in fig. 7. The inset shows a measured 3d spectrum of Ce02 (similar to the one in fig. 8) and one can realize that the theory represents the experimental data quite well (Kotani and Jo 1986). 

O. Gunnarsson and K. Schonhammer, Many-body formulation of spectra of mixed valence systems 103... 

Such models, applied by Gunnarsson and Schonhammer [616], or by Jo and Kotani [618] have provided a very successful framework for reconciling results from a wide variety of different spectroscopies (X-ray photoabsorption (XAS), photoemission (PES), bremstrahlung isochromat spectroscopy (BIS), etc.) by the use of only a few adjustable parameters. 

Gunnarsson, O., and K. Schonhammer, 1987, in Handbook on the Physics and Chemistry of Rare Earths, Vol. 10, eds K.A. Gschneidner, L. Eyring and S. Hufner (North-Holland, Amsterdam). 

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