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1
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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
|
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.
2
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Comparison between Mo BIS and Mo K-Edge Absorption Spectrum

100%
Sobczak E.
Acta Physica Polonica A
|
1992
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vol. 82
|
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}.
3
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Extended Structure of Fe BIS as Compared to Fe K EXAFS

64%
Sobczak E., Mobilio S.
Acta Physica Polonica A
|
1992
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vol. 82
|
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

Utility of Aureobasidium pullulans and pullulan in food biotechnology

64%
Gniewosz M., Sobczak E.
Biotechnologia
|
1999
|
issue 2
81-93
EN
Fungus Aureobasidium pullulans is the producer of numerous valuable substances (enzymes, melanins, antibiotics). Pullulan - the product of metabolism of A. pullulans strains has a great potential utility in food industry. Since chemical synthesis of pullulan is expensive, a great effort has been made to improve the productivity of A. pullulans strains. The application of mutagenesis (UV light, several chemical mutagenes) allowed to receive mutants with high productivity of that compound. The most promising mutants are those which produce pullulan with
5
Content available remote

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

64%
Sobczak E., Nietubyć R.
Acta Physica Polonica A
|
1995
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vol. 87
|
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.
6
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Surface Studies of Re_{3}Fe_{5}O_{12} Garnets, ReFeO_{3} Orthoferrites and ReVO_{4} Orthovanadates

51%
Sobczak E., Żymierska D., Ebel H.
Acta Physica Polonica A
|
1996
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vol. 89
|
issue 3
329-333
EN
The X-ray photoelectron spectra for Re_{3}Fe_{5}O_{12} garnets, ReFeO_{3} orthoferrites and ReVO_{4} orthovanadates have been measured by using Mg K_{α} radiation. The O 1s, Re 4d, Fe 2p, and V 2p photoelectron spectra were studied. A very big difference was observed between ReFeO_{3} orthoferrites and ReVO_{4} orthovanadates, mainly the Fe 2p_{3/2} lines were double broader than V 2p_{3/2} ones, and the O 1s line is split by about 1.6 eV for orthoferrites, while this line is single for orthovanadates. The O 1s peak at 531.8 eV with intensity about 70% of the main peak is interpreted as originated from a charge fluctuation between oxygen and iron ions due to superexchange interaction.
7
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Photoemission of Cd(0001) Using Synchrotron Radiation

51%
Sobczak E., Nilsson P., Karlsson K.
Acta Physica Polonica A
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1992
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vol. 82
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issue 2
337-339
EN
Photoemission spectra for the Cd(0001) surface in the Γ̅-M̅ azimuth were calculated using a multiple scattering method. The emission angle of the photoelectrons θ was kept constant and equal to 35°. The photon energy was varied from 20 eV to 27 eV. The self-consistent potential used in the calculations was generated by the scalar-relativistic LMTO method. A modified image potential for the surface barrier potential was applied. The photoemission spectra show a strong surface state peak at an energy of about 1 eV below the Fermi level.
8
Content available remote

Fe Clusters in Fe Intercalated Fullerite

51%
Sobczak E., Żymierska D., Byszewski P., Traverse A.
Acta Physica Polonica A
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1997
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vol. 91
|
issue 2
447-450
EN
The local structure around Fe ions in the C_{60}Fe_{2} fullerites before and after heat treatment in temperature of 850 K was investigated by means of Fe K edge X-ray absorption near edge structure and extended X-ray absorption near edge structure methods. The X-ray absorption measurements were performed at liquid nitrogen temperature using synchrotron radiation in transmission mode. The X-ray absorption near edge structure and extended X-ray absorption near edge structure studies showed that the heat treatment of the C_{60}Fe_{2} fullerite at temperature 850 K causing an irreversible transition from monoclinic to fcc structure is accompanied with changes in the state of Fe ions, part of them forms clusters in bcc structure, while others turn to Fe^{3+} ions bonded to fullerenes.
9
Content available remote

X-Ray Absorption Studies of Fe_{73.5}Cu_{1}Nb_{3}Si_{15.5}B_{7} Amorphous and Nanocrystalline Alloys

45%
Swilem Y., Sobczak E., Nietubyć R., Ślawska-Waniewska A., Dynowska E.
Acta Physica Polonica A
|
1997
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vol. 91
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issue 5
883-886
EN
The nanocrystalline state of the formally amorphous alloy Fe_{73.5}Cu_{1}Nb_{3}Si_{15.5}B_{7} is achieved by a heat treatment at temperatures between 500°C and 600°C. The XANES and EXAFS methods were applied for investigation of local structure and chemical bonding around Fe atoms in amorphous and nanocrystalline alloys. The Fe K absorption spectra were measured in the transmission mode at room temperature for Fe_{73.5}Cu_{1}Nb_{3}Si_{15.5}B_{7} amorphous and nanocrystalline alloys and compared with the spectra for Fe metallic foil and Fe_{3}Si polycrystalline samples.
10
Content available remote

Partial Probabilities of X-Ray Bremsstrahlung Transitions

45%
Nietubyć R., Sobczak E., S̆imůnek A., Vackár̆ J., S̆ipr O.
Acta Physica Polonica A
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1997
|
vol. 91
|
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.
11
Content available remote

C_{60}FeC_{60} Complexes in Fe Intercalated Fullerite Studied by X-Ray Absorption

39%
Sobczak E., Traverse A., Nietubyć R., Swilem Y., Byszewski P., Żymierska D.
Acta Physica Polonica A
|
1997
|
vol. 91
|
issue 5
877-881
EN
The aim of Fe K edge XANES and EXAFS studies is to reveal the local structure around Fe ions in C_{60}Fe_{x} intercalated fullerites. The measurements are performed in transmission mode at LN_{2} temperature for C_{60}Fe_{x} powder samples and other materials: ferrocene Fe(C_{5}H_{5})_{2}, Fe metal foil and α-Fe_{2}O_{3}. The main result is that the XAFS spectra of the C_{60}Fe_{2} intercalate is almost identical to that of ferrocene and very different from α-Fe and α-Fe_{2}O_{3}. The results support opinion that in the C_{60}Fe_{x} intercalates the ferrocene-like bonds in complexes C_{60}FeC_{60} are formed. Additionally, the XAFS spectra showed that neither remarkable amount of Fe metallic clusters nor oxidized iron particles are present in the C_{60}Fe_{x} sample.
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