Electronic structure in the bulk and at the surface of lanthanide materials. A detailed study with X-ray emission and inverse photoemission

This dissertation is concerned with the occupied and unoccupied electronic structure of lanthanide materials. With surface sensitive electron-excited x-ray emission spectroscopy (XES) we could experimentally determine a surface and bulk partial density of states (p-DOS) for the metals Lanthanum, Lutetium and Samarium. From calculations of the O3-XE transition probability we anticipate a three times higher probability for s-like than for d-like electrons to fill the 5p3/2-hole; this was confirmed experimentally. A surface state could not be observed in any XE spectrum. The emission from this surface state of dZ2-symmetry is suppressed by more than one order of magnitude relative to emissions from s-like valence states. In the case of Samarium we could identify satellite emission in XES. Photoemission (PE) measurements were needed to determine the binding energy of 5p-1 hole states - including the 5p-replica shift* in Samarium. For the determination of the Samarium p-DOS we developed a model descripting the generation of IPE background radiation in XES, caused by Auger electrons which are created in a radiationless decay of the 5p core-hole. The absence of O2-XE in all metals could be explained with intense Auger decays of the 5p1/2-hole. With the present work we have set the basics for further surface sensitive XE measurements, e.g. at 3d transition metals. In the second part of this work we have measured the occupied and unoccupied electronic structure of LaS, LaSe and LaTe. With measurements of the O3-XE in the Lanthanum-Chalcogenides we could demonstrate the transfer of s-like valence electrons from the Lanthanum atom to the Chalcogen atom. Furthermore, the binding energy of the state at the Lanthanum atom was determined. The surface core-level shift is smaller by 25 % in the Chalcogenides than in La-metal. We also describe a theoretical model, which qualitatively explains the observed larger shifts of the core-level binding energy in PE than in IPE from Lanthan-Chalcogenides