B. Solleder

Electron guiding through insulating nanocapillaries

We simulate the electron transmission through insulating Mylar (polyethylene terephthalate, or PET) capillaries. We show that the mechanisms underlying the recently discovered electron guiding are fundamentally different from those for ion guiding. Quantum reflection and multiple near-forward scattering rather than the self-organized charge up are key to the transmission along the capillary axis irrespective of the angle of incidence. We find surprisingly good agreement with recent data. Our simulation suggests that electron guiding should also be observable for metallic capillaries.

Simulation of attosecond streaking of electrons emitted from a tungsten surface

First time-resolved photoemission experiments employing attosecond streaking of electrons emitted by an extended ultraviolet pump pulse and probed by a few-cycle near-infrared pulse found a time delay of about 100 as between photoelectrons from the conduction band and those from the

Fast-atom diffraction at surfaces

4f

Influence of inelastic processes on fast-atom-surface diffraction

core level of tungsten. We present a microscopic simulation of the emission time and energy spectra employing a classical transport theory. Emission spectra and streaking images are well reproduced. Different contributions to the delayed emission of core electrons are identified: larger emission depth, slowing down by inelastic-scattering processes, and possibly, energy-dependent deviations from the free-electron dispersion. We find delay times near the lower bound of the experimental data.

Potential energy - induced nanostructuring of insulator surfaces by impact of slow, very highly charged ions

Fast helium atoms diffracted at alkali-halide surfaces under grazing angles of incidence exhibit intriguing diffraction patterns. The persistence of quantum coherence is remarkable, considering high surface temperatures and high (keV) kinetic energies of the incident atoms. Dissipative and decohering effects such as the momentum transfer between the incident helium atoms and the surface influence the diffraction patterns and control the width of the diffraction peaks, but they are weak enough to preserve the visibility of the diffration patterns. We perform an ab initio simulation of the quantum diffraction of fast helium beams at a LiF (100) surface in the (110) direction. Our results agree well with recent experimental diffraction data.

Spin-dependent low-energy electron scattering and transport in metals

Diffraction of fast helium atoms at alkali-halide surfaces under grazing angles of incidence shows intriguing diffraction patterns. The persistence of quantum coherence is remarkably strong, even though high surface temperatures and high (keV) kinetic energies of the incident atoms would strongly suggest the dominance of dissipative and decohering processes. The main source of decoherence is the excitation or absorption of surface vibrations upon impact. The momentum transfer between the surface and the incident helium atom depends on the amplitude of the thermal vibrations of the surface atoms and the energy of the incident particle. We present an ab initio simulation of the quantum diffraction of fast helium beams at a LiF (100) surface in the (110) direction, and compare with recent experimental diffraction data.

Collisions of Slow Highly Charged Ions with Surfaces

We have recently shown that the impact of individual slow highly charged ions is able to induce permanent nano-sized hillocks on the surface of a CaF2 single crystal. The experimentally observed threshold of the projectile ion potential energy necessary for hillock formation could be linked to a solid-liquid phase transition (nano-melting). In this contribution we report on similar nano-sized surface modifications as a result of the potential energy of impacting highly charged ions for other surfaces.

Creation of nanohillocks on CaF2 surfaces by single slow highly charged ions.

We study spin-dependent scattering and transport of low energy electrons (≤ 500 eV) through metals employing a classical transport theory within which electron trajectories are simulated as a sequence of stochastic scattering events. Elastic as well as spin-dependent inelastic processes are included in our model simulating the complete secondary electron cascade. We apply our model to spin-polarization measurements of electrons emitted from magnetized Fe after impact of unpolarized primary electrons. We find good agreement with experimental data.

Suppression of Decoherence in Fast-Atom Diffraction at Surfaces

Progress in the study of collisions of multiply charged ions with surfaces is reviewed with the help of a few recent examples. They range from fundamental quasi-one electron processes to highly complex ablation and material modification processes. Open questions and possible future directions will be discussed.