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1
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Extended X-ray Bremsstrahlung Isochromat Fine Structure of SiO_{2}

100%
Sobczak E., Nietubyć R.
Acta Physica Polonica A
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1995
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vol. 87
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issue 3
649-656
EN
X-ray bremsstrahlung isochromat of amorphous SiO_{2} deposited on Si crystal was measured in an energy range up to 250 eV above the threshold. Extended X-ray bremsstrahlung isochromat he structure (EXBIFS) was observed up to 150 eV for SiO_{2} studied. The Fourier transform of EXBIFS showed two peaks originated from first and second neighbors around silicon and oxygen ions. Model calculations of EXBIFS of amorphous SiO_{2} were performed in terms of single scattering of spherical waves and compared with experimental results.
2
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Partial Probabilities of X-Ray Bremsstrahlung Transitions

100%
Nietubyć R., Sobczak E., S̆imůnek A., Vackár̆ J., S̆ipr O.
Acta Physica Polonica A
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1997
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vol. 91
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issue 5
841-846
EN
High-energy electrons bombarding a solid produce X-ray bremsstrahlung radiation, which is one of few elementary processes occurring during electron-solid interactions. Photon emission results from electron transition to an unoccupied electron state above the Fermi level. In this work matrix elements of X-ray bremsstrahlung transitions were calculated for solids containing elements from N (Z=7) to Pd (Z=46) and photon energies 1487 eV and 5415 eV. It was found that in the case of light elements the X-ray bremsstrahlung transitions to s-type final states dominate over all other symmetries. It was also shown that X-ray bremsstrahlung transition probabilities increase with decreasing photon energy and increasing atomic number Z. Dependence of X-ray bremsstrahlung transition probabilities on the electron final state energy is also presented in this work.
3
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Extended Structure of Fe BIS as Compared to Fe K EXAFS

100%
Sobczak E., Mobilio S.
Acta Physica Polonica A
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1992
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vol. 82
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issue 2
333-335
EN
The X-ray bremsstrahlung isochromat of Fe was measured for the photon energy 5415 eV in an extended energy range up to 300 eV above the threshold and compared to the Fe K-edge X-ray absorption spectrum. The Fourier analysis was performed for both spectra. It was stated that the extended structure of the Fe bremsstrahlung isochromat is clearly visible and is characteristic of the Fe bcc structure. Using the beat-node method, the distance between first and second shells in the bcc Fe was obtained quite close to the crystallographic value.
4
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Comparison between Mo BIS and Mo K-Edge Absorption Spectrum

100%
Sobczak E.
Acta Physica Polonica A
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1992
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vol. 82
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issue 2
329-332
EN
The extended X-ray bremsstrahlung isochromat fine structure of bcc Mo for the photon energy 5415 eV is studied and compared with the extended X-ray absorption fine structure at the Mo K-edge from the literature. In both spectra a minimum of oscillation amplitude is observed at the momentum 4.2 and 5.3 Å^{-1} for extended X-ray bremsstrahlung isochromat fine structure and extended X-ray absorption fine structure respectively, which is caused by the Ramsauer-Townsend effect at 5.5 Å^{-1} and by beating effect at 3.7 Å^{-1} from the first and second atomic shells. The Fourier transform of Mo extended X-ray bremsstrahlung isochromat fine structure was found to be in good agreement with the radial structure function of bcc Mo only in the case when the integration was performed in momentum range below 4.2 Å^{-1}.
5
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Extended X-Ray Bremsstrahlung Isochromat Fine Structure

100%
Sobczak E.
Acta Physica Polonica A
|
1993
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vol. 83
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issue 2
135-155
EN
Main aspects concerning a new method of extended X-ray bremsstrahlung isochromat fine structure (EXBIFS) are specified and discussed. The EXBIFS effect is studied here by application of a single-scattering theory, which explains well the experimental phenomenon that EXBIFS of Cu and Pd is strikingly similar to the p partial density of states, although the s- and d-symmetry contributions are not negligible. The single-scattering model of EXBIFS has been successfully applied for explanation of temperature effects resulting in a smearing of oscillations for big k values. It is established here that interatomic distances can be evaluated from EXBIFS by means of the single-scattering theory and the Fourier analysis.
6
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Photoemission and Inverse Photoemission Studies of SiO_{2}

80%
Sobczak A., Nietubyć R., Sobczak J. W.
Acta Physica Polonica A
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1994
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vol. 86
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issue 5
837-843
EN
Occupied and unoccupied electron states of amorphous silicon dioxide film supported on Si crystal are studied by using X-ray photoemission and, for the first time, X-ray inverse photoemission (X-ray bremsstrahlung isochromat method). A special care was undertaken to minimize decomposition of silicon oxide during X-ray bremsstrahlung measurements. The experimental spectra are compared with theoretical band structure calculations for amorphous SiO_{2} from the literature and good overall agreement is found.
7
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Thermally Stimulated Electron Emission from K-Bi-GICs

80%
Chrzanowski J., Klimkiewicz R., Morawski A.
Acta Physica Polonica A
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1998
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vol. 93
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issue 3
531-537
EN
The results of the investigations of thermally stimulated electron emission from graphite submitted to intercalation of K-Bi alloy, in the temperature range of 100-400 K, are presented. Total and partial pressure in the measuring chamber in relation to the temperature of the sample are also reported. The insertion of a K-Bi alloy into the interlayers of graphite considerably changes thermally stimulated electron emission properties. The emission images I(T) depend on the content of intercalate and the emission maxima obtained at temperatures of about 170 and 210 K are conditioned by the desorption of a gas while the total pressure above the different samples is of the same order. The desorption of gases at a temperature over 250 K does not cause any increase in the electron emission.
8
Content available remote

Electron Structure of d-Transition Metals and their Alloys on the Basis of EELS Study

70%
Kołodziej H. B.
Acta Physica Polonica A
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1995
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vol. 88
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issue 1
171-176
EN
Analysis of characteristic electron energy losses in reflection from the surface provides information on electron and band structure of the solid state. Study of transition metals, their alloys (Fe-N, Zn-Ni) and amorphous alloys Fe_{78}Si_{9}B_{13} show that there are two subsets of electron gas characterized by different oscillation frequency. The presence of independent components of volume plasmons corresponding to s and d electrons is an evidence that despite collectivization both the subsets preserve individual features characteristic of the structure of an isolated atom. From the energy losses the following quantities are determined: the effective mass (μ) for particular electron subsets, the Fermi energy (E_{F}), the band widths (δE) for s and d electrons and contribution of the subsets to the metal conductivity (γ). The obtained results for metals are compared to analogous data for alloys both in crystalline and amorphous phase.
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