No abstract available

[en] Large electron yields, compared to theoretical predictions, have often been observed in the high-energy part of the electron spectra in collisions of energetic ions with atomic, molecular or solid targets. The relative enhancement of the electron emission yield at high energies can be especially strong in ion-solid collisions. In this work, following a brief overview, recent experimental evidences are presented for Fermi-shuttle type accelerating electron scattering sequences in ion-atom collisions. Signatures for double (projectile-target, P-T), triple (projectile-target-projectile, P-T-P) and quadruple (P-T-P-T) scattering sequences have been found in different collision systems. Our new results indicate the presence of even higher-order scattering contributions in the collisions of few keV energy N⁺ ions with inert gas atoms. The observations support that high-energy electrons produced by accelerating scattering sequences may play a significant role in ion-solid collisions

[en] We have studied the energy loss of slow (velocity v∼0.06 a.u.) highly charged Ar⁹⁺ ions scattered at large angles from a clean Au(1 1 1) single crystal surface. The influence of the scattering geometry on the energy loss has been investigated for different incidence angles (5 deg. ≤ψ≤37.5 deg.) and scattering angles (30 deg. ≤θ≤75 deg.). At large angles (ψ=37.5 deg., θ=75 deg.), the main peak in the measured energy spectrum agrees well with the position expected for binary elastic scattering. With decreasing incidence angle a shift of the 'binary peak' to lower energy is observed, and for decreasing scattering angles, a shift of the binary peak to higher energy than calculated by kinematics is found. The additional energy loss seen at small ψ (ψ=5 deg.) is interpreted by inelastic energy loss. A model calculation which combines s rate-equation description of Auger cascades, recapture to the surface with a Firsov type model and image charge acceleration during ion-surface interaction is used to describe the data

[en] Dielectronic recombination of Pb⁵³⁺ has been studied and a resonance is detected only ∼0.1 meV above the ground state. The possibility to determine the 4p_1/2-4s_1/2 energy splitting with a similar accuracy from the determination of the resonance position is discussed. Such a precision can only be achieved by calculations which treat QED in a many-body environment at levels which can still not be reached. A fully relativistic many-body calculation of the splitting is described and the uncertainties are discussed

No abstract available

[en] The energy distributions of positrons scattered around 0 deg. from H₂O have been measured in coincidence with the remnant ions (H₂O⁺, OH⁺ and H⁺) at 100 eV and 153 eV incident energies. The maxima of the distributions (d²σ/dE₊dΩ) associated with the production of OH⁺ and H⁺ are about 5-10 times smaller than that for H₂O⁺. At both incident energies, a small shoulder has been observed at ∼28 eV in the energy loss spectra associated with H₂O⁺ production possibly arising from a shake-up band associated with the 2a₁ orbital. The branching ratios for the H⁺ and HO⁺ fragments are also presented.

[en] We measured the energy and angular distribution of ionic fragments produced by the interaction of 1-220 keV Xe²²⁺ ions with water molecules. The measured distributions strongly depend on the projectile charge state and energy, as seen from the comparison of the results with previously published data for 5 keV He²⁺, and 2 and 90 keV Ne^(3-9)+ ions. A significant forward-backward asymmetry of the energy and intensity of the H⁺ fragments is observed. The interpretation of the experimental results is guided by means of classical trajectory simulations based on a Coulomb explosion model. The experimental finding of a strong enhancement of the H⁺ yield at 90 deg. is attributed to an alignment of the molecular axis during the collision and the momentum transfer from the slow projectile.

[en] The coherence and imaging beamline I13 is dedicated to hard x-ray imaging on the micro- and nano-lengthscale, performing microscopy either in direct or reciprocal space. For both, lens-based and lensless imaging, two independent stations will be operated in a separate building at a distance of 250 m from the source. The imaging branch will perform in-line phase contrast imaging and tomography over a large field of view in the 6- to 35-keV energy range. In addition, it will be possible to switch to full-field microscopy with 50-nm spatial resolution. Other microscopies will be developed according to the scientific needs. Resolution beyond the limitations given by the detector and x-ray optics will be achieved with techniques working in the far field. Coherent x-ray diffraction (CXRD) and other coherent diffraction imaging techniques such as ptychography will also be implemented on the same 'coherence' branch. The beamline hosts a number of innovative features such as the so-called 'mini-beta' layout for electron optics in the storage ring or new concepts for beamline instrumentation. The stations will be operational in 2011.

[en] We report an experimental study of guided transmission of low-energy (200-350 eV) electrons through highly ordered Al₂O₃ nanocapillaries with large aspect ratio (140 nm diameter and 15 μm length). The nanochannel array was prepared using self-ordering phenomena during a two-step anodization process of a high-purity aluminum foil. The experimental results clearly show the existence of the guiding effect, as found for highly charged ions. The guiding of the electron beam was observed for tilt angles up to 12 degree sign . As seen for highly charged ions, the guiding efficiency increases with decreasing electron incident energy. The transmission efficiency appeared to be significantly lower than observed for highly charged ions and, moreover, the intensity of transmitted electrons significantly decreases with decreasing impact energy

[en] Interatomic energy and charge transfer in a Xe doped Ar cluster have been investigated. Besides interatomic Coulombic decay (ICD), electron transfer mediated decay (ETMD) seems to play a significant role in the relaxation process of heterogeneous systems which is in strong contrast to pristine clusters. Ar 2p electrons have been measured in coincidences with cluster fragments. The high resolution in time and energy of the detectors enabled us to determine the site of ionization on the cluster and the kind of the resulting fragments.