共查询到20条相似文献,搜索用时 15 毫秒
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《Journal of Electron Spectroscopy and Related Phenomena》1998,94(3):259-270
Magnetic dichroism in off-normal photoemission from valence bands of ferromagnets is studied by both symmetry considerations and numerical relativistic calculations. In general set-ups (light polarization, incidence and emission directions, magnetization direction), dichroism is either due to change of the light polarization or due to magnetization reversal, or due to both. Relations between photoemission intensities for different set-ups lead to the definition of asymmetries in order to probe the origin of the dichroism. Numerical relativistic photoemission calculations provide quantitative results for prototypical systems: Ni/Cu(001) with perpendicular magnetization, Co/Cu(001) with in-plane magnetization, and non-magnetic Cu(001). 相似文献
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The overview covers selected topics on magnetic
dichroism in atomic core level photoemission: the geometrical
model in photoionization of laser polarized atoms and its
generalization, contributions to the complete experiment from
magnetic dichroism studies and nondipole effects in magnetic
dichroism. 相似文献
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I. I. Pronin M. V. Gomoyunova D. E. Malygin D. V. Vyalykh Yu. S. Dedkov S. L. Molodtsov 《Physics of the Solid State》2008,50(3):553-556
The effect of magnetic linear dichroism in photoemission of Fe 3p electrons was used to investigate the magnetic properties of the Si(100)2 × 1 surface on which iron films up to 10 monolayers thick were deposited at room temperature under ultrahigh vacuum. The experiments were performed with linearly polarized light (at a photon energy of 135 eV) incident at an angle of 30° to the surface. The photoelectron spectra were measured in a narrow solid angle oriented along the normal to the sample surface for two opposite magnetization directions which were parallel to the surface plane and perpendicular to the polarization vector of the light wave. An analysis of the data obtained showed that the effect has a threshold character and appears after deposition of eight Fe monolayers, when the ferromagnetic silicide Fe3Si is formed on the surface. 相似文献
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A method is described to achieve virtually full absorption of microwave power in an overdense plasma column of low collision frequency. 相似文献
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Some aspects of atomic and solid-state contributions to the angular dependence of photoemission from core levels, and their relevance and utility in the study of surfaces, are reviewed from a personal and historical perspective. In particular, the role played by dipole angular dependence in photoelectron diffraction and X-ray absorption spectroscopy, and by both dipole and non-dipole effects in X-ray standing wave studies are highlighted. 相似文献
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In this communication we present theoretical demonstration of electron dichroism in the relativistic (e, 2e) process for K-shell ionization of atoms in non-coplanar asymmetric geometry. The theoretical formalism has been developed
in plane wave Born approximation and in this approximation the triple differential cross-section (TDCS) has been expressed
as a product of kinematical factors and atomic structure functions. The longitudinal spin asymmetry in the relativistic (e, 2e) process on K-shell of atoms has been shown to depend on the interference between the transition charge and component of
the transition current in the direction perpendicular to the scattering plane. Further, the longitudinal spin asymmetry has
been shown to depend on incident electron energy, atomic number of the target, azimuthal angle of the ejected electron and
scattered electron angle. 相似文献
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Emission spectra and the energy distribution of the excited-state population density of atoms and ions in erosion laser plasma
from CuInS2 with various crystal-structure orderings are analyzed. It is shown that increased ordering of the target crystal structure
causes the excited-state energies of indium atoms generated in the laser erosion plume to increase and that sulfur atoms always
emit only in transitions from highly excited states. The ratio of relative ion concentrations in the laser plasma plume is
Cu+/In+/S+ = 0.3/0.08/2, which corresponds neither to the atomic ratio of Cu/In/S (1/1/2) in the target nor to the ratio of ionization
energies. The results are explained by recombination processes for ions and by the atomization specifics of the CuInS2 target exposed to long-wavelength radiation. The atomization consists essentially of dissociative processes expressed by
CuInS2 → CuInS + S and CuInS2 → Cu + InS + S. The electron temperature of polycrystal (single-crystal) plasma at a distance of 1 mm from the target is
0.3 eV (0.4 eV) for atoms and 1.3 eV (2.7 eV) for ions and varies negligibly for plasma up to a distance of 7 mm from the
target.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 2, pp. 217–223, March–April, 2008. 相似文献
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Jahnke T Weber T Landers AL Knapp A Schössler S Nickles J Kammer S Jagutzki O Schmidt L Czasch A Osipov T Arenholz E Young AT Díez Muiño R Rolles D García de Abajo FJ Fadley CS Van Hove MA Semenov SK Cherepkov NA Rösch J Prior MH Schmidt-Böcking H Cocke CL Dörner R 《Physical review letters》2002,88(7):073002
We have measured the angular distributions of 1s photoelectrons excited by circularly and linearly polarized light from fixed-in-space CO and N2 molecules, in the vicinity of their shape resonances. A strong circular dichroism, i.e., a strong dependence on the sense of rotation of the polarization vector of the photons, is found for both molecules. State-of-the-art one-electron multiple scattering and partially correlated random phase approximation calculations are in good agreement with many, but not all, aspects of the experimental data. 相似文献
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K. Starke Z. Hu F. Hübinger E. Navas G. Kaindl G. van der Laan 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(2):171-178
Magnetic circular dichroism in lanthanide 4
f photoemission (PE) multiplets was studied across the 4
d-4
f excitation threshold for the example of Tb metal. The combined experimental and theoretical analysis demonstrates that resonant
enhancement of the 4
f PE signal and large magnetic contrast in the PE intensity are obtained simultaneously, when the excitation energy is tuned
to the absorption-edge maximum for parallel orientation of magnetization and circular-polarization light helicity.
Received 23 February 1999 相似文献
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Emissions from high-density potassium atoms excited by either nanosecond or femtosecond laser pulses
A study of the emissions, for high atomic density potassium, under nanosecond (ns) or femtosecond (fs) two-photon excitation
is presented. It is shown that the parametric emissions (connected to the |6S1/2〉↔|5P3/2〉↔|4S1/2〉 transitions) strongly depend on the excitation intensity and they have a nonlinear and a linear response region, in both
kinds of excitation. In the ns excitation, the calculated results of a four-level atomic configuration agree well with the
experimental ones, in the case of the path-1 parametric emissions (|6S1/2〉↔|5P3/2〉↔|4S1/2〉) for certain excitation and atomic density parameters. Also, the fields of the atomic path-2 (|6S1/2〉↔|4P3/2〉↔|4S1/2〉) are numerically shown to be amplified spontaneous emission (ASE) or cascade ASE without population inversion, due to the
population transfer to the |6S1/2〉 level initially and its subsequent collapse to the lower levels. In the fs excitation, only parametric emissions are observed
from both atomic paths and there are not yet numerical calculations available to compare with. However, there is strong similarity
of the experimental ns and fs results for the path-1 parametric emissions. 相似文献
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Ebrahim Ghanbari-Adivi Azime Najafabadi Velayati 《Central European Journal of Physics》2014,12(3):192-202
The four-body Coulomb-Born distorted-wave approximation with correct boundary conditions (CBDW-4B) is applied to the K-shell positronium formation from multi-electron atoms at intermediate and high impact energies. In the present approach, both K-shell electrons are treated as active electrons. For collisions of positrons with helium, carbon, and neon atoms, both the post and prior forms of the transition amplitude are calculated and the corresponding differential and integral cross sections are compared with the results of the three-body version of the formalism (CBDW-3B). In order to investigate the effects of the static electronic correlations on the process, initial bound states of the active electrons in helium atoms are described by Hylleraas and Silverman wave functions. Also for positronium formation from helium atoms the obtained cross sections are compared with the available experimental data and also with the results of the other theories. 相似文献
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L. Vriens 《Physics letters. A》1976,55(6):331-332
Cross sections are calculated for near-resonant light scattering from n=2 excited hydrogen atoms. Previous derivations of these cross sections are shown to be incorrect. 相似文献
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H. Kitamura 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,52(1-3):147-150
Molecular-orbital calculations are performed to elucidate electronic structures and optical properties of lithium clusters in which several K-shell electrons are simultaneously excited to the valence levels. It is shown that relaxation of valence electrons around localized core holes influences the photoabsorption near-edge spectra significantly. The spectra in the excited state are modified from those in the ground state due to the presence of initial core holes. Potential energy surfaces are calculated for core-ionized Li9 z+ clusters, which exhibit bound states for z≤3. The present cluster calculations would serve as prototypical models of laser-excited hollow atom solids with applications to X-ray optics. 相似文献
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The population ratio of Zeeman sublevels of atoms on the surface of superfluid helium droplets (T=0.37 K) has been measured. Laser induced fluorescence spectra of K atoms are measured in the presence of a moderately strong magnetic field (2.9 kG). The relative difference between the two states of circular polarization of the exciting laser is used to determine the electron spin polarization of the ensemble. Equal fluorescence levels indicate that the two spin sublevels of the ground-state K atom are equipopulated, within 1%. Thermalization to 0.37 K would give a population ratio of 0.35. We deduce that the rate of spin relaxation induced by the droplet must be <520/s. For the K2 triplet dimer we find instead full thermalization of the spin. 相似文献