L-edge x-ray absorption spectra ofγ− and α−cerium

Abstract

The $L$ absorption spectra of $\gamma - \mathrm{and} \alpha -\mathrm{Ce}$ have been measured. The $L_2$ and $L_3$ spectra of both systems show white lines, but $\alpha -\mathrm{Ce}$ exhibits an additional peak 9 eV above the white line. In a mixed-valence model $\alpha -\mathrm{Ce}$ has a ratio [${\mathrm{Ce}}^{3+}$] to [${\mathrm{Ce}}^{4+}$] of about 0.8 to 0.2. However, this interpretation is in conflict with Compton scattering. The measured extended x-ray-absorption fine-structure (EXAFS) spectra of $\alpha -\mathrm{Ce}$ allow only for one value $E_0$ (zero of photoelectron energy). It is an open question why only one value $E_0$ is observed in the EXAFS of mixed-valent systems.