“…The latter process is of physical relevance also to gastarget experiments as e.g. performed by Wittmann and Anddi [35,25]. In this case, the observed atomic polarization is produced by impact parameter selection.…”
Section: Discussionmentioning
confidence: 96%
“…In our model circular polarization (S:I=0) is essentially determined by the modified charge density (25) at the surface plane. Because 7 < 0 in the high-velocity regime, Eq.…”
Section: {10 B~>0 (28) B(b)= Bx<0mentioning
confidence: 99%
“…A very simple model of this anisotropic interaction process is that of surface channeling referred to as "impact parameter selection". It is based on information gained from energy-loss measurements [25] at ions reflected from a flat surface under grazing incidence conditions. It turns out that most of the projectiles are reflected at the outermost layer and that only a small fraction of them (depending on Z) penetrates the atomic surface layer.…”
Section: Comparison With the Density-gradient Modelmentioning
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 sin fl dependence of the circular polarization on the tilt angle ft. Model calculations for beamsurface scattering show good agreement with experimental data for the relative Stokes parameters.
“…The latter process is of physical relevance also to gastarget experiments as e.g. performed by Wittmann and Anddi [35,25]. In this case, the observed atomic polarization is produced by impact parameter selection.…”
Section: Discussionmentioning
confidence: 96%
“…In our model circular polarization (S:I=0) is essentially determined by the modified charge density (25) at the surface plane. Because 7 < 0 in the high-velocity regime, Eq.…”
Section: {10 B~>0 (28) B(b)= Bx<0mentioning
confidence: 99%
“…A very simple model of this anisotropic interaction process is that of surface channeling referred to as "impact parameter selection". It is based on information gained from energy-loss measurements [25] at ions reflected from a flat surface under grazing incidence conditions. It turns out that most of the projectiles are reflected at the outermost layer and that only a small fraction of them (depending on Z) penetrates the atomic surface layer.…”
Section: Comparison With the Density-gradient Modelmentioning
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 sin fl dependence of the circular polarization on the tilt angle ft. Model calculations for beamsurface scattering show good agreement with experimental data for the relative Stokes parameters.
“…This gives us a handle to systematically vary to, the time of excited term formation, and the time of postformation interaction in order to learn about the interaction mechanism involved. As warned earlier [13] and proved recently [14] the post-formation Stark interaction in hydrogen-like systems in the surface electric field F=-grad U(y) tends to obscure by unpredictable phase-developments the information on the acutal excited term formation. We therefore try to reduce the influence of the Stark interaction to a negligible minimum by definitely avoiding hydrogen-like systems for our studies of the excited term formation -noting, however, that for other questions H-like systems may be of interest.…”
Section: Basic Considerations On Experimentsmentioning
confidence: 95%
“…In the experiments to be discussed we try to approach the so called "ideal experiment" [13] as good as possible. On an ideally clean and flat polycrystalline or single crystal surface, described by a collective planar potential U(y) an incoming ion with perpendicular energy E• moves up to a distance of closest approach r 0 and is nearly specularly reflected after some energy loss and excitation.…”
Section: Basic Considerations On Experimentsmentioning
The analysis of charge state distributions after the interaction of fast Li-and N-ions with a surface at grazing incidence at energies between 50 and 350keV yields for Li a strongly suppressed and for N an enhanced fraction of neutrals in comparison to the beam-foil interaction. These findings are supported by corresponding alkali-spectra which are dominated by lines from transitions in singly ionized atoms. The experiments are consistently interpreted in terms of a two step model: (1) collisional excitation in the close vicinity of the surface and (2) modification of this population by resonant electron transfer from (to) non localized states in the conduction (valence) band to (from) the ion. The model is also applied to interpret recent beam-foil experiments where preferential populations of Rydberg levels in highly ionized atoms were found.
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