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An anomaly in the hysteresis loop of the polarisation of KNbO 3 is observed at low frequencies. This gives a value for the remanent polarisation which is an order of magnitude larger than that in the frequency regime of traditional measurements. We correlate this observation with the specific properties of the surfaces of ABO 3 -type perovskites. Surface analytical methods are used to characterise the structure of electrochemically induced surface layers of KNbO 3 . We find that the chemical composition, together with the crystallographic structure of the surface, differs drastically from the crystal bulk. In particular we observe a network of extended defects which serves as a fast diffusion path for oxygen and potassium and allows special segregation and redox processes.

Monolayers of CaF 2 on Si(111) are characterized by photoemission spectra of the valence and core electrons. Three different phases can be distinguished, depending on the annealing temperature. The near edge structure at teh F 1s edge was found to be strongly polarization dependent. By comparison of these absorption spectra with X-α-SCF cluster calculations, and with bulk spectra SiF bonding can be ruled out, a Ca bonded interface being ascertained.

After almost ten years of successful operation at a bending magnet beamline of HASYLAB, the Flipper monochromator was transferred to a 32-pole wiggler/undulator. With new grazing incidence optics the original energy range of 15–450 eV could be extended to more than 1500 eV. The gain in intensity is approximately two orders of magnitude. Undulator effects are observed between 36 and 900 eV and contribute considerably to this intensity gain. Monochromators of the Flipper type are ideally matching the emission characteristics of undulators. The main problem with wigglers at high energy storage rings is the heat load on the optical elements.

In Nd, Sm, Eu and Gd the decay of the 3d-4f resonance excitation into different photoionization channels (4f, 4d) was measured. Spin-orbit splitting of the 3d hole dominates the spectra. Depop- ulation of the 3d 3 2 due to the M4M5N57 Auger effect leads to a much larger 3d 5 2 :3d 3 2 int than in absorption. The use of synchrotron radiation from an undulator was decisive.

We present a SEXAFS (surface extended X-ray absorption fine structure) investigation of oxygen adsorbed on Si(100) at the oxygen K absorption edge (EK=535 eV), in the photon energy range 500–800 eV. The oxygen uptake on Si(100) at room temperature reaches a saturation at about one monolayer coverage, where the (2×1) reconstruction of the clean surface is lost. Our results demonstrate the following: the oxygen atoms occupy two types of bridge positions, namely between Si atoms belonging to the first layer and between Si atoms belonging to different topmost layers. The bridge site is characterized by a bond distance of 1.65 A and a Si−O−Si bond angle of ∼120°. No evidence of other types, of adsorption geometries is found nor the presence of adsorbed molecular oxygen is observed.