High energy resolution spectroscopy of electrons emitted from deep core transitions induced by hard X-rays in solids is playing an increasingly significant role in the studies of the local electronic structure around specific atoms having key importance for materials properties, as well as in the quantitative analysis of buried interfaces or nanostructures in materials of great practical relevance. KLL Auger spectra photoexcited from 3d metals using resonant conditions provide information on the density of the 4p unoccupied electronic states through the shape of the spectra near the K-shell photoionization threshold [1]. Although the resonant KLL spectra of Cu and Ni metals, corrected for background from electrons scattered inelastically within the solids, can be successfully interpreted by the help of a simple model based on resonant inelastic X-ray scattering theory with partial density of states obtained from cluster molecular orbital calculations, in the case of Ni the agreement between model and experiment is only qualitative [1]. In the present work, using the semiclassical dielectric response model developed by Yubero and Tougaard [2] for describing electron energy losses during photoexcitation and electron transport, it is shown that the differences between the simple theoretical approximation mentioned above and the experiment can be attributed mainly to the contribution of intrinsic type electron energy losses, induced by the sudden appearance of the core hole(s) during the Auger process. For Ni metal, at about 10 eV energy loss, this intrinsic type loss contribution to the resonant KLL Auger spectrum is significantly larger than in the case of the Cu metal.
This work has been supported by the DESY/HASYLAB and the European Community under Contract RII3-CT-2004-506008 (IA-SFS).
[1] L. Kövér, W. Drube, Z. Berényi, I. Cserny, V. R. R. Medicherla, T. Ishii, H. Ikeno, H. Adachi, Surf. Sci. 601(2007)1085.
[2] Yubero F., Tougaard S., Phys. Rev. B71(2005)045414.
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