Angular and energy differential electron emission cross sections in collisions between antiprotons and helium atoms

We present theoretical singly- and doubly-differential ionization cross sections in collisions between antiprotons and helium atoms at 50 and 100 keV impact energies. The calculations were performed within the frame work of the continuum distorted wave eikonal initial state approximation and a three-body classical trajectory Monte Carlo method. We find clear evidence for the formation of the anti-cusp in the differential distributions.     

Electrical response of molecular systems: the power of self-interaction corrected kohn-sham theory

The accurate prediction of electronic response properties of extended molecular systems has been a challenge for conventional, explicit density functionals. We demonstrate that a self-interaction correction (SIC) implemented rigorously within Kohn-Sham theory via the optimized effective potential (OEP) yields polarizabilities close to the ones from highly accurate wave-function-based calculations and exceeding the quality of exact-change OEP. The orbital structure obtained with the OEP-SIC functional and approximations to it are discussed.     

Theory of optical polarization due to electron capture from localized target states by fast ions

The excited-projectile state density matrix is derived from the impact-parameter version of the Oppenheimer-Brinkman-Kramers approximation for a one electron-capture process from localized target states. The result is used to determine the Stokes parameters of the emitted light. General conditions for the production of atomic orientation are investigated and the connection to a recently published classical model is established. Large values of atomic orientation and alignment are found for capture into a hydrogenic 2p state of the projectile. A simple model for the beam-tilted-foil interaction yields a sinβ dependence of the circular polarization on the tilt angleβ. Model calculations for beam-surface scattering show good agreement with experimental data for the relative Stokes parameters.     

Group-theoretical classification of angular momentum coherences in hydrogen

Results of photon-scattered atom coincidence measurements are presented for Mg-inert gas collisions. A polarisation analysis of the collision induced Mg(3¹ P-3¹ S) photons emitted perpendicular to the scattering plane was carried out at 1 keV collision energy as a function of the impact parameter. From these data the quantum-mechanical scattering amplitudes for the excitation of one of the two available Mg 3s-valence electrons are derived. The results are compared with the corresponding ones for the Mg⁺-inert gas collisions. A good qualitative understanding of the mechanism can be obtained.     

Generation of GW radiation pulses from a VUV free-electron laser operating in the femtosecond regime

Experimental results are presented from vacuum-ultraviolet free-electron laser (FEL) operating in the self-amplified spontaneous emission (SASE) mode. The generation of ultrashort radiation pulses became possible due to specific tailoring of the bunch charge distribution. A complete characterization of the linear and nonlinear modes of the SASE FEL operation was performed. At saturation the FEL produces ultrashort pulses (30-100 fs FWHM) with a peak radiation power in the GW level and with full transverse coherence. The wavelength was tuned in the range of 95-105 nm.     

Photoproduction of η -mesons off protons

Photoproduction of η -mesons was studied with the Crystal-Barrel detector at ELSA for photon energies in the range from 0.75 to 3GeV. Total and differential cross-sections are presented. The η mesons are detected in two decay modes, in η → 2γ and in η → 3π⁰ → 6γ . The cross-sections vary slowly as functions of energy and η production angle suggesting that only few resonances make significant contributions to the cross-section. For photon energies above 1.5GeV, the differential cross-sections show a strong forward peak due to meson exchanges in the t channel. A comparison of the η -photoproduction cross-sections with SAID and MAID as well as with a partial-wave analysis performed on our data in combination with other data sets shows good agreement. The Bonn-Gatchina partial-wave analysis suggests that the largest contribution to η photoproduction for energies below 3GeV proceeds via three resonances, the well-known N(1535)S ₁₁ , via N(1720)P ₁₃ , and a newly suggested N(2070)D ₁₅ .     

Zur Definition von Hyperfunktionen

Hyperfunctions are defined by means of functional analysis and within the theory of local cohomology of sheaves. In the same way we study the hyperfunctions of coherent analytic sheaves and the vectorvalued situation.Applications as generalized Bochner-Hartogs- and edge-of-the-wedge-theorems and solutions of boundary value-problems for sections of coherent analytic sheaves will follow.     

Time resolved Fano resonances

Recent advances in the generation of sub-fs extreme ultraviolet pulses and attosecond metrology have opened up the possibility to trace the time evolution of electronic wave packets inside atoms in pump-probe experiments. We investigate the feasibility of observing the buildup of a Fano resonance in the time domain by attosecond streaking techniques. A time-resolved resonance is initialized by a sub-fs extreme ultraviolet-pump pulse in the presence of a synchronized phase-controlled probe laser pulse. The time evolution of the coherent superposition of resonant state and continuum is mapped onto a modulation of the electron spectrum as a function of the time delay between pump and probe pulse. (super-)Coster-Kronig transitions with lifetimes of approximately 400 asec( are identified as prime candidates.     

Experimental investigations to establish acoustic fatigue design charts

The investigations presented in this paper show that the acoustically induced stresses in stiffened panels can be estimated with sufficient accuracy. Due consideration is given to the effect of the parameters aspect ratio, stringer pitch, curvature, skin thickness and skin doublers. The stresses can be evaluated by means of random SN curves for different joining techniques.