We report recent results on the performance of FLASH (Free Electron Laser in Hamburg) operating at a wavelength of 13.7 nm where unprecedented peak and average powers for a coherent EUV radiation source have been measured. In the saturation regime the peak energy approached 170 µJ for individual pulses while the average energy per pulse reached 70 µJ. The pulse duration was in the region of 10 femtoseconds and peak

Many scientific disciplines ranging from physics, chemistry and biology to material sciences, geophysics and medical diagnostics need a powerful X-ray source with pulse

Colloids of nanocrystalline tin dioxide containing 9.1 at. % and 16.7 at. % antimony have been prepared by the coprecipitation method. High-resolution transmission electron microscopy (TEM) images show crystalline particles in the 2–6 nm size regime. X-ray powder diffraction patterns of nanocrystalline powders obtained by drying the colloids and heating to 100 °C indicate the same rutile lattice structure known from bulk SnO2. On heating to 500 °C in air, the nanocrystalline powder shows a slight increase in particle size but especially a change in color from yellowish to bluish which is accompanied by the development of n-type conductivity. The coordination of antimony in the SnO2 nanocrystallites has been investigated by extended x-ray absorption fine structure measurements (EXAFS) at the Sb K-edge at 5 K while its valence state was determined by near edge x-ray absorption fine structure measurements (XANES) at the Sb L1 edge. The Sb higher neighbor shell distances in the doped material differ from the corresponding distances in Sb2O3 or Sb2O5 but are identical to those in tin dioxide, indicating that antimony is almost completely incorporated into the tin dioxide lattice despite the high doping level. XANES measurements reveal that a large fraction of SbIII employed during the synthesis is already oxidized to SbV at low temperatures. On the basis of these observations, a two-step model for the formation of n-conductive Sb-doped SnO2 nanocrystals is given and quantitatively discussed with respect to the data.

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Thiolcapped CdTe nanocrystals (18 Å diameter) are investigated by extended x-ray absorption fine structure (EXAFS) measurements between 8 and 290 K at the Cd and Te K-edge. The different coordination sites of Cd in the particle core and at the surface are identified and are consistent with a CdTe particle core which is covered by a Cd–SR surface layer (R=organic rest). We are able to study individually changes of the properties of the interior and the surface of the nanoparticle with respect to bulk material. Structure and dynamics of the CdTe nanocrystals are mainly altered by the requirement of heteroepitaxial growth at the interface between the CdTe core and the Cd–SR shell. As a consequence, bond lengths and Debye temperatures of particle core and surface show a tendency to accommodate in thiolcapped CdTe nanocrystals. The trends in bond lengths variation observed in the experiment can be reproduced by calculations of the strain distribution induced by the lattice mismatch in a simplified isotropic model of a spherical CdTe nanoparticle which is encapsulated by a CdS bulklike shell. The experiment also shows a significantly enhanced static disorder both in particle core and surface. In contrast, the asymmetry of the radial pair distribution function of the Cd–S surface bonds is strongly elevated whereas the Cd–Te bonds in the interior of the particle show no enhancement with respect to bulk material. Experimental coordination numbers at the Cd and Te K-edge and the Cd/Te edge jump ratio are in good agreement with the expected values of a Cd54Te32(SR)528−-nanocrystal. This structural model is a larger homolog of a series of analogous CdS nanoparticles and consists of a CdTe tetrahedron which is partially coated by a Cd–SR surface layer.