The Experts below are selected from a list of 255 Experts worldwide ranked by ideXlab platform
Andreas Wucher - One of the best experts on this subject based on the ideXlab platform.
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influence of the polar angle of incidence on electronic substrate excitations in kev self bombardment of solid silver
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2011Co-Authors: S Hanke, A Duvenbeck, B Weidtmann, Andreas WucherAbstract:Abstract We present a computer simulation study on the influence of the polar angle of incidence on electronic substrate excitations in the self-sputtering of silver. For the bombardment of a silver target with 5-keV Ag atoms, we employ a standard molecular dynamics code to follow the microscopic particle dynamics within the Atomic Collision cascade following the primary particle impact. The transfer of kinetic energy of cascade atoms into the electronic subsystem of the metal is treated in terms of the Lindhard model of electronic stopping and an electron promotion model describing the generation of hot electrons in close binary Collisions. The transport of excitation energy away from the spot of generation is treated in a diffusive manner. The calculations yield a time- and space-dependent excitation energy density E ( r → , t ) that can be converted into an electron temperature profile T e ( r → , t ) . The results of our calculations show an angle-dependent duration of the initial electron temperature peak at the surface which coincides with the time the projectile needs to cross the first layer of the model crystal.
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influence of the polar angle of incidence on secondary ion formation in self sputtering of silver
Surface and Interface Analysis, 2011Co-Authors: B Weidtmann, S Hanke, A Duvenbeck, Andreas WucherAbstract:The influence of the projectile impact angle on secondary ion formation was studied using a computer simulation model applied to the bombardment of an amorphous silver crystal by 5-keV Ag atoms. The model employs a molecular dynamics (MD) scheme for the description of particle dynamics within the Atomic Collision cascade. The electronic degree of freedom is treated within the framework of a free electron gas model incorporating kinetic excitation by electronic friction and electron promotion. Transport of the excitation energy away from the spot of generation is treated by a diffusive approach. In combination with a rate equation model for electronic charge transfer an individual ionization probability a + is assigned to each sputtered particle. The results reveal that the average ionization probability of sputtered atoms increases upon the transition from normal to oblique incidence. The dependence of α + on the emission velocity of ejected atoms is traced back to the temporal structure of the excitation profile induced after projectile impact.
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modeling hot electron generation induced by electron promotion in Atomic Collision cascades in metals
Physical Review B, 2008Co-Authors: A Duvenbeck, B Weidtmann, Oliver Weingart, Andreas WucherAbstract:We present a computer simulation model for the investigation of electron promotion processes in Atomic Collision cascades in metals. The model combines molecular dynamics and molecular orbital calculations to describe the formation of hot electrons in close Atomic Collisions. We apply this model to a set of Collision cascades initiated by the impact of a 5-keV silver atom onto an Ag(111) surface. The calculations show that about 15% of the bombarding energy originally introduced into the solid is dissipated into the generation of hot electrons in close Collisions. Furthermore, we find that the nascent excitation energy spectrum closely resembles a power law $f({E}_{\text{exc}})\ensuremath{\propto}{E}_{\text{exc}}^{\ensuremath{-}\ensuremath{\delta}}$ with exponents $\ensuremath{\delta}\ensuremath{\approx}2\char21{}3$.
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the role of electronic friction of low energy recoils in Atomic Collision cascades
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2007Co-Authors: A Duvenbeck, Oliver Weingart, Volker Buss, Andreas WucherAbstract:We investigate the influence of low-energy recoils with respect to the electronic excitation of solids generated in Atomic Collision cascades. It is found that the electronic friction experienced by recoil atoms moving with kinetic energies below 10 eV contributes substantially to the total excitation energy dissipated into electronic degrees of freedom. The Collision dynamics, on the other hand, remain virtually unchanged if the friction loss of these particles is switched on or off. This is illustrated by looking at the yield, emission sites and energies of sputtered surface atoms.
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electron promotion and electronic friction in Atomic Collision cascades
New Journal of Physics, 2007Co-Authors: A Duvenbeck, Oliver Weingart, Volker Buss, Andreas WucherAbstract:We present a computer simulation model for the space- and time-resolved calculation of electronic excitation energy densities in Atomic Collision cascades. The model treats electronic friction as well as electron promotion as a source term of electronic energy that is carried away from the original point of excitation according to a nonlinear diffusion equation. While the frictional source is treated within the Lindhard model of electronic stopping, electron promotion is described using diabatic correlation curves derived from ab initio molecular orbital energy level calculations in combination with the Landau–Zener curve crossing model. Results calculated for two selected Collision cascades show that the electron promotion mechanism may contribute significantly to the excitation energy density in the cascade volume, giving rise to distinct peaks of the local electron temperature at the surface. This contribution is essentially restricted to the first 100 fs after the projectile impact and may therefore be of significance for either external or internal kinetic electron emission. At later times, where the bombardment-induced particle kinetics lead to the sputter ejection of material from the surface, the excitation is shown to be primarily governed by electronic friction. This finding is important in light of excitation and ionization probabilities of sputtered particles.
A Duvenbeck - One of the best experts on this subject based on the ideXlab platform.
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influence of the polar angle of incidence on electronic substrate excitations in kev self bombardment of solid silver
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2011Co-Authors: S Hanke, A Duvenbeck, B Weidtmann, Andreas WucherAbstract:Abstract We present a computer simulation study on the influence of the polar angle of incidence on electronic substrate excitations in the self-sputtering of silver. For the bombardment of a silver target with 5-keV Ag atoms, we employ a standard molecular dynamics code to follow the microscopic particle dynamics within the Atomic Collision cascade following the primary particle impact. The transfer of kinetic energy of cascade atoms into the electronic subsystem of the metal is treated in terms of the Lindhard model of electronic stopping and an electron promotion model describing the generation of hot electrons in close binary Collisions. The transport of excitation energy away from the spot of generation is treated in a diffusive manner. The calculations yield a time- and space-dependent excitation energy density E ( r → , t ) that can be converted into an electron temperature profile T e ( r → , t ) . The results of our calculations show an angle-dependent duration of the initial electron temperature peak at the surface which coincides with the time the projectile needs to cross the first layer of the model crystal.
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influence of the polar angle of incidence on secondary ion formation in self sputtering of silver
Surface and Interface Analysis, 2011Co-Authors: B Weidtmann, S Hanke, A Duvenbeck, Andreas WucherAbstract:The influence of the projectile impact angle on secondary ion formation was studied using a computer simulation model applied to the bombardment of an amorphous silver crystal by 5-keV Ag atoms. The model employs a molecular dynamics (MD) scheme for the description of particle dynamics within the Atomic Collision cascade. The electronic degree of freedom is treated within the framework of a free electron gas model incorporating kinetic excitation by electronic friction and electron promotion. Transport of the excitation energy away from the spot of generation is treated by a diffusive approach. In combination with a rate equation model for electronic charge transfer an individual ionization probability a + is assigned to each sputtered particle. The results reveal that the average ionization probability of sputtered atoms increases upon the transition from normal to oblique incidence. The dependence of α + on the emission velocity of ejected atoms is traced back to the temporal structure of the excitation profile induced after projectile impact.
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modeling hot electron generation induced by electron promotion in Atomic Collision cascades in metals
Physical Review B, 2008Co-Authors: A Duvenbeck, B Weidtmann, Oliver Weingart, Andreas WucherAbstract:We present a computer simulation model for the investigation of electron promotion processes in Atomic Collision cascades in metals. The model combines molecular dynamics and molecular orbital calculations to describe the formation of hot electrons in close Atomic Collisions. We apply this model to a set of Collision cascades initiated by the impact of a 5-keV silver atom onto an Ag(111) surface. The calculations show that about 15% of the bombarding energy originally introduced into the solid is dissipated into the generation of hot electrons in close Collisions. Furthermore, we find that the nascent excitation energy spectrum closely resembles a power law $f({E}_{\text{exc}})\ensuremath{\propto}{E}_{\text{exc}}^{\ensuremath{-}\ensuremath{\delta}}$ with exponents $\ensuremath{\delta}\ensuremath{\approx}2\char21{}3$.
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the role of electronic friction of low energy recoils in Atomic Collision cascades
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2007Co-Authors: A Duvenbeck, Oliver Weingart, Volker Buss, Andreas WucherAbstract:We investigate the influence of low-energy recoils with respect to the electronic excitation of solids generated in Atomic Collision cascades. It is found that the electronic friction experienced by recoil atoms moving with kinetic energies below 10 eV contributes substantially to the total excitation energy dissipated into electronic degrees of freedom. The Collision dynamics, on the other hand, remain virtually unchanged if the friction loss of these particles is switched on or off. This is illustrated by looking at the yield, emission sites and energies of sputtered surface atoms.
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electron promotion and electronic friction in Atomic Collision cascades
New Journal of Physics, 2007Co-Authors: A Duvenbeck, Oliver Weingart, Volker Buss, Andreas WucherAbstract:We present a computer simulation model for the space- and time-resolved calculation of electronic excitation energy densities in Atomic Collision cascades. The model treats electronic friction as well as electron promotion as a source term of electronic energy that is carried away from the original point of excitation according to a nonlinear diffusion equation. While the frictional source is treated within the Lindhard model of electronic stopping, electron promotion is described using diabatic correlation curves derived from ab initio molecular orbital energy level calculations in combination with the Landau–Zener curve crossing model. Results calculated for two selected Collision cascades show that the electron promotion mechanism may contribute significantly to the excitation energy density in the cascade volume, giving rise to distinct peaks of the local electron temperature at the surface. This contribution is essentially restricted to the first 100 fs after the projectile impact and may therefore be of significance for either external or internal kinetic electron emission. At later times, where the bombardment-induced particle kinetics lead to the sputter ejection of material from the surface, the excitation is shown to be primarily governed by electronic friction. This finding is important in light of excitation and ionization probabilities of sputtered particles.
Thomas Pfeifer - One of the best experts on this subject based on the ideXlab platform.
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roadmap on photonic electronic and Atomic Collision physics i light matter interaction
Journal of Physics B, 2019Co-Authors: K Ueda, E Sokell, S Schippers, F Aumayr, H R Sadeghpour, J Burgdorfer, C Lemell, Xiaomin Tong, Thomas PfeiferAbstract:Author(s): Ueda, K; Sokell, E; Schippers, S; Aumayr, F; Sadeghpour, H; Burgdorfer, J; Lemell, C; Tong, XM; Pfeifer, T; Calegari, F; Palacios, A; Martin, F; Corkum, P; Sansone, G; Gryzlova, EV; Grum-Grzhimailo, AN; Piancastelli, MN; Weber, PM; Steinle, T; Amini, K; Biegert, J; Berrah, N; Kukk, E; Santra, R; Muller, A; Dowek, D; Lucchese, RR; McCurdy, CW; Bolognesi, P; Avaldi, L; Jahnke, T; Schoffler, MS; Dorner, R; Mairesse, Y; Nahon, L; Smirnova, O; Schlatholter, T; Campbell, EEB; Rost, JM; Meyer, M; Tanaka, KA | Abstract: © 2019 IOP Publishing Ltd. We publish three Roadmaps on photonic, electronic and Atomic Collision physics in order to celebrate the 60th anniversary of the ICPEAC conference. In Roadmap I, we focus on the light-matter interaction. In this area, studies of ultrafast electronic and molecular dynamics have been rapidly growing, with the advent of new light sources such as attosecond lasers and x-ray free electron lasers. In parallel, experiments with established synchrotron radiation sources and femtosecond lasers using cutting-edge detection schemes are revealing new scientific insights that have never been exploited. Relevant theories are also being rapidly developed. Target samples for photon-impact experiments are expanding from atoms and small molecules to complex systems such as biomolecules, fullerene, clusters and solids. This Roadmap aims to look back along the road, explaining the development of these fields, and look forward, collecting contributions from twenty leading groups from the field.
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roadmap on photonic electronic and Atomic Collision physics i light matter interaction
Journal of Physics B, 2019Co-Authors: K Ueda, E Sokell, S Schippers, F Aumayr, H R Sadeghpour, J Burgdorfer, C Lemell, Xiaomin Tong, Thomas PfeiferAbstract:We publish three Roadmaps on photonic, electronic and Atomic Collision physics in order to celebrate the 60th anniversary of the ICPEAC conference. In Roadmap I, we focus on the light-matter intera ...
Oliver Weingart - One of the best experts on this subject based on the ideXlab platform.
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modeling hot electron generation induced by electron promotion in Atomic Collision cascades in metals
Physical Review B, 2008Co-Authors: A Duvenbeck, B Weidtmann, Oliver Weingart, Andreas WucherAbstract:We present a computer simulation model for the investigation of electron promotion processes in Atomic Collision cascades in metals. The model combines molecular dynamics and molecular orbital calculations to describe the formation of hot electrons in close Atomic Collisions. We apply this model to a set of Collision cascades initiated by the impact of a 5-keV silver atom onto an Ag(111) surface. The calculations show that about 15% of the bombarding energy originally introduced into the solid is dissipated into the generation of hot electrons in close Collisions. Furthermore, we find that the nascent excitation energy spectrum closely resembles a power law $f({E}_{\text{exc}})\ensuremath{\propto}{E}_{\text{exc}}^{\ensuremath{-}\ensuremath{\delta}}$ with exponents $\ensuremath{\delta}\ensuremath{\approx}2\char21{}3$.
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the role of electronic friction of low energy recoils in Atomic Collision cascades
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2007Co-Authors: A Duvenbeck, Oliver Weingart, Volker Buss, Andreas WucherAbstract:We investigate the influence of low-energy recoils with respect to the electronic excitation of solids generated in Atomic Collision cascades. It is found that the electronic friction experienced by recoil atoms moving with kinetic energies below 10 eV contributes substantially to the total excitation energy dissipated into electronic degrees of freedom. The Collision dynamics, on the other hand, remain virtually unchanged if the friction loss of these particles is switched on or off. This is illustrated by looking at the yield, emission sites and energies of sputtered surface atoms.
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electron promotion and electronic friction in Atomic Collision cascades
New Journal of Physics, 2007Co-Authors: A Duvenbeck, Oliver Weingart, Volker Buss, Andreas WucherAbstract:We present a computer simulation model for the space- and time-resolved calculation of electronic excitation energy densities in Atomic Collision cascades. The model treats electronic friction as well as electron promotion as a source term of electronic energy that is carried away from the original point of excitation according to a nonlinear diffusion equation. While the frictional source is treated within the Lindhard model of electronic stopping, electron promotion is described using diabatic correlation curves derived from ab initio molecular orbital energy level calculations in combination with the Landau–Zener curve crossing model. Results calculated for two selected Collision cascades show that the electron promotion mechanism may contribute significantly to the excitation energy density in the cascade volume, giving rise to distinct peaks of the local electron temperature at the surface. This contribution is essentially restricted to the first 100 fs after the projectile impact and may therefore be of significance for either external or internal kinetic electron emission. At later times, where the bombardment-induced particle kinetics lead to the sputter ejection of material from the surface, the excitation is shown to be primarily governed by electronic friction. This finding is important in light of excitation and ionization probabilities of sputtered particles.
F Aumayr - One of the best experts on this subject based on the ideXlab platform.
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roadmap on photonic electronic and Atomic Collision physics iii heavy particles with zero to relativistic speeds
Journal of Physics B, 2019Co-Authors: F Aumayr, K Ueda, E Sokell, S Schippers, H R Sadeghpour, Frederic Merkt, T F Gallagher, Barry F Dunning, P ScheierAbstract:We publish three Roadmaps on photonic, electronic and Atomic Collision physics in order to celebrate the 60th anniversary of the ICPEAC conference. Roadmap III focusses on heavy particles: with zer ...
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roadmap on photonic electronic and Atomic Collision physics i light matter interaction
Journal of Physics B, 2019Co-Authors: K Ueda, E Sokell, S Schippers, F Aumayr, H R Sadeghpour, J Burgdorfer, C Lemell, Xiaomin Tong, Thomas PfeiferAbstract:Author(s): Ueda, K; Sokell, E; Schippers, S; Aumayr, F; Sadeghpour, H; Burgdorfer, J; Lemell, C; Tong, XM; Pfeifer, T; Calegari, F; Palacios, A; Martin, F; Corkum, P; Sansone, G; Gryzlova, EV; Grum-Grzhimailo, AN; Piancastelli, MN; Weber, PM; Steinle, T; Amini, K; Biegert, J; Berrah, N; Kukk, E; Santra, R; Muller, A; Dowek, D; Lucchese, RR; McCurdy, CW; Bolognesi, P; Avaldi, L; Jahnke, T; Schoffler, MS; Dorner, R; Mairesse, Y; Nahon, L; Smirnova, O; Schlatholter, T; Campbell, EEB; Rost, JM; Meyer, M; Tanaka, KA | Abstract: © 2019 IOP Publishing Ltd. We publish three Roadmaps on photonic, electronic and Atomic Collision physics in order to celebrate the 60th anniversary of the ICPEAC conference. In Roadmap I, we focus on the light-matter interaction. In this area, studies of ultrafast electronic and molecular dynamics have been rapidly growing, with the advent of new light sources such as attosecond lasers and x-ray free electron lasers. In parallel, experiments with established synchrotron radiation sources and femtosecond lasers using cutting-edge detection schemes are revealing new scientific insights that have never been exploited. Relevant theories are also being rapidly developed. Target samples for photon-impact experiments are expanding from atoms and small molecules to complex systems such as biomolecules, fullerene, clusters and solids. This Roadmap aims to look back along the road, explaining the development of these fields, and look forward, collecting contributions from twenty leading groups from the field.
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roadmap on photonic electronic and Atomic Collision physics i light matter interaction
Journal of Physics B, 2019Co-Authors: K Ueda, E Sokell, S Schippers, F Aumayr, H R Sadeghpour, J Burgdorfer, C Lemell, Xiaomin Tong, Thomas PfeiferAbstract:We publish three Roadmaps on photonic, electronic and Atomic Collision physics in order to celebrate the 60th anniversary of the ICPEAC conference. In Roadmap I, we focus on the light-matter intera ...
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roadmap on photonic electronic and Atomic Collision physics ii electron and antimatter interactions
Journal of Physics B, 2019Co-Authors: S Schippers, K Ueda, E Sokell, F Aumayr, H R Sadeghpour, Igor Bray, Klaus Bartschat, Andrew James Murray, Jonathan Tennyson, Alexander DornAbstract:We publish three Roadmaps on photonic, electronic and Atomic Collision physics in order to celebrate the 60th anniversary of the ICPEAC conference. In Roadmap II we focus on electron and antimatter interactions. Modern theoretical and experimental approaches provide detailed insight into the many body quantum dynamics of leptonic Collisions with targets of varying complexity ranging from neutral and charged atoms to large biomolecules and clusters. These developments have been driven by technological progress and by the needs of adjacent areas of science such as astrophysics, plasma physics and radiation biophysics. This Roadmap aims at looking back along the road, explaining the evolution of the field, and looking forward, collecting contributions from eighteen leading groups from the field.
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modelling of fast neutral li beams for fusion edge plasma diagnostics
Plasma Physics and Controlled Fusion, 1999Co-Authors: R Brandenburg, F Aumayr, J Schweinzer, S Fiedler, Hannspeter WinterAbstract:We present an experimental and theoretical study on the modelling of fast Li beams which are used for diagnostics of fusion edge plasmas. The Atomic Collision database utilized for modelling the Li beam attenuation has been revised and extended by detailed investigations of populations resulting from ion impact excitation. We obtain good agreement between measured and calculated Li(nl) populations for an Li beam passing the edge plasma region of the ASDEX Upgrade tokamak and WENDELSTEIN 7 AS stellarator, respectively, at IPP Garching.