Collisions of slow highly charged ions with surfaces

in Fainstein, P.D.; Lima, M.A.P.; Miraglia, J.E. (Eds.) et al Photonic, Electronic and Atomic Collisions, Proceedings of the XXIV International Conference (2006)

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 ... [more ▼]

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. [less ▲]

Multi-electron dynamics for neutralization of highly charged ions near surfaces

in Vacuum (2004), 73(1), 3-7

We present a simulation of the neutralization of highly charged ions in front of a lithium fluoride surface including the close-collision regime above the surface. The present approach employs a Monte ... [more ▼]

We present a simulation of the neutralization of highly charged ions in front of a lithium fluoride surface including the close-collision regime above the surface. The present approach employs a Monte-Carlo solution of the Liouville master equation for the joint probability density of the ionic motion and the electronic population of the projectile and the target surface. It includes single as well as double particle-hole (de)excitation processes and incorporates electron correlation effects through the conditional dynamics of population strings. For slow projectiles and normal incidence, the ionic motion depends sensitively on the interplay between image acceleration towards the surface and repulsion by an ensemble of positive hole charges in the surface ("trampoline effect"). For Ne10+ we find that image acceleration is dominant and no collective backscattering high above the surface takes place. (C) 2004 Elsevier Ltd. All rights reserved. [less ▲]

Liouville master equation for multielectron dynamics: Neutralization of highly charged ions near a LiF surface

in Physical Review. A (2003), 67(1),

We present a simulation of the neutralization of highly charged ions in front of a lithium fluoride surface including the close-collision regime above the surface. The present approach employs a Monte ... [more ▼]

We present a simulation of the neutralization of highly charged ions in front of a lithium fluoride surface including the close-collision regime above the surface. The present approach employs a Monte Carlo solution of the Liouville master equation for the joint probability density of the ionic motion and the electronic population of the projectile and the target surface. It includes single as well as double particle-hole (de)excitation processes and incorporates electron correlation effects through the conditional dynamics of population strings. The input in terms of elementary one- and two-electron transfer rates is determined from classical trajectory Monte Carlo calculations as well as quantum-mechanical Auger calculations. For slow projectiles and normal incidence, the ionic motion depends sensitively on the interplay between image acceleration towards the surface and repulsion by an ensemble of positive hole charges in the surface ("trampoline effect"). For Ne10+ we find that image acceleration is dominant and no collective backscattering high above the surface takes place. For grazing incidence, our simulation delineates the pathways to complete neutralization. In accordance with recent experimental observations, most ions are reflected as neutral or even as singly charged negative particles, irrespective of the charge state of the incoming ions. [less ▲]

Hollow-ion formation in microcapillaries

in Physical Review. A (2001), 64(4),

Transmission of highly charged ions through microcapillaries is studied theoretically by a classical trajectory simulation. The interaction of highly charged ions with the internal surface of the ... [more ▼]

Transmission of highly charged ions through microcapillaries is studied theoretically by a classical trajectory simulation. The interaction of highly charged ions with the internal surface of the capillary is treated within the framework of dielectric-response theory. The simulation is based on the classical over-the-barrier model modified for open cylindrical surfaces. The multielectron evolution and relaxation is taken into account as a stochastic event sequence. We consider N6+ and Ne10+ with an energy of 2.1 keV/amu passing through a metallic microcapillary of Ni. We analyze the distance of closest approach. the angular distribution, and the distribution of the mean occupation numbers of n shells of highly charged ions. We find the resulting charge state distribution of transmitted projectiles in good agreement with recent measurements. Implications for nanotube targets will be discussed. [less ▲]

Vertical incidence of slow Ne10+ ions on an LiF surface: Suppression of the trampoline effect

in Nuclear Instruments and Methods in Physics Research. Section B, Beam Interactions with Materials and Atoms (2001), 182

We present a Monte Carlo simulation of the neutralization of a slow Ne10+ ion in vertical incidence on an LiF(100) surface. The rates for resonant electron transfer between surface F- ions and the ... [more ▼]

We present a Monte Carlo simulation of the neutralization of a slow Ne10+ ion in vertical incidence on an LiF(100) surface. The rates for resonant electron transfer between surface F- ions and the projectile are calculated using a classical trajectory Monte Carlo simulation, We investigate the influence of the hole mobility on the neutralization sequence. It is shown that backscattering above the surface due to the local positive charge up of the surface ("trampoline effect") does not take place. (C) 2001 Elsevier Science B.V. All rights reserved. [less ▲]

Curve-crossing analysis for potential sputtering of insulators

in Surface Science (2000), 451(1-3), 197-202

We develop a theoretical model for the recently observed threshold for potential sputtering of LiF by slow singly and doubly charged ions. The threshold coincides with the potential energy to create a ... [more ▼]

We develop a theoretical model for the recently observed threshold for potential sputtering of LiF by slow singly and doubly charged ions. The threshold coincides with the potential energy to create a cold hole in the valence band of LiF by resonant neutralization. We calculate the level shift of the incident ion and the deformation of the valence band under the influence of the projectile. Resonant neutralization becomes possible for ions with recombination energies larger than 10 eV in agreement with the experimental findings. (C) 2000 Elsevier Science B.V. All rights reserved. [less ▲]

Threshold for potential sputtering of LiF

in Physical Review Letters (1999), 83(19), 3948-3951

We have measured total sputtering yields for impact of slow (less than or equal to 100 eV) singly and doubly charged ions on LiF. The minimum potential energy necessary to induce potential sputtering (PS ... [more ▼]

We have measured total sputtering yields for impact of slow (less than or equal to 100 eV) singly and doubly charged ions on LiF. The minimum potential energy necessary to induce potential sputtering (PS) from UF was determined to be about 10 eV. This threshold coincides with the energy necessary to produce a cold hole in the valence band of LiF by resonant neutralization. This allows the first unambiguous identification of PS induced by cold holes. Further stepwise increase of the sputtering yield with higher projectile potential energies provides evidence for additional defect-mediated sputtering mechanisms operative in alkali halides. [less ▲]