Full-text resources of PSJD and other databases are now available in the new Library of Science.
Visit https://bibliotekanauki.pl

Refine search results

Journals help

  1. 39 Acta Physica Polonica A

Years help

  1. 1 2015

  2. 1 2014

  3. 2 2012

  4. 3 2010

  5. 2 2009

More...
Authors help

  1. 7 Kisiel A.

  2. 5 Markowski R.

  3. 4 Oleszkiewicz J.

  4. 4 Ławniczak-Jabłońska K.

  5. 3 Burattini E.

More...
Preferences help
Polish version English version Language
enabled [disable] Abstract
Number of results

Results found: 39

Number of results on page
first rewind previous Page / 2 next fast forward last

Search results

Search:
in the keywords:  78.70.Dm
help Sort By:

help Limit search:
first rewind previous Page / 2 next fast forward last
1
Content available remote

Determination by X-Ray Absorption of Redox Induced Structural Changes in Iron-Sulfur Cluster F_{x} in Photosystem I

100%
Sagi I., Bunker G., Hochman Y., Carmeli C., Zeng M. T.
Acta Physica Polonica A
|
1997
|
vol. 91
|
issue 5
871-875
EN
X-ray absorption spectra of photosystem I core protein containing F_{x}, the low potential iron-sulfur cluster was measured. X-ray absorption of the iron K-edge was obtained in the reduced and oxidized forms of F_{x}. An edge shift of 0.5 eV to lower energy and a change in the X-ray absorption near edge structure was observed. Some of the alterations in edge shape of F_{x} are interpreted to indicate structural changes of the iron-sulfur cluster in F_{x} upon reduction.
2
Content available remote

L_{1} Absorption Edge of the 4f Heavy Rare-Earth Metals

100%
Shrivastava B., Joshi S.
Acta Physica Polonica A
|
1992
|
vol. 81
|
issue 3
385-392
EN
The wavelengths of the L_{1} absorption edges of the 4f heavy rare-earth metals (^{65}Tb to ^{71}Lu) have been measured using a 40 cm curved crystal spectrograph of the Cauchois-type in the transmission mode. The measured values have been found to fit nicely in the modified Moseley diagrams. The absence of the white lines at the L_{1} edges of the rare earths in metallic form and its occurrence in their compounds has been discussed.
3
Content available remote

Amorphous Bi-Ge-S(Se) Systems Studied by X-Ray Ge K Emission and Absorption Bands

100%
Drahokoupil J., Drbohlav I., Polčik M., Tichý L.
Acta Physica Polonica A
|
1994
|
vol. 86
|
issue 5
721-726
EN
The X-ray Ge K absorption (emission) bands were measured in the stoichiometric glass system (GeS_{2})_{x}(Bi_{2}S_{3})_{1-x} (x = 0 ÷ 0.5) and in the Ge_{20}Bi_{y}Se_{80-y} system (y = 0, 7 and 13). The results do not confirm the existence of the Ge-Bi bond and they imply that the GeS_{2}-clusters are formed in both studied systems.
4
Content available remote

Chemical Shifts at K-Absorption Edges of Transition Metals Admixed To ZnS and ZnSe

100%
Iwanowski R. J., Ławniczak-Jabłońska K., Traverse A.
Acta Physica Polonica A
|
1997
|
vol. 91
|
issue 4
803-808
EN
This paper gives the experimental evidence of systematic X-ray K-absorption edge studies in an effort to analyse the effect of cation chemical shift in the group of compounds type Zn_{1-x}M_{x}A (M = Mn, Fe, Co, Ni; A = S, Se). The observed chemical shift was found practically independent of the choice of anion, whereas it revealed a noticeable decrease when passing from Mn to Zn. The effect was ascribed to the change of the 3d shell occupation. The calculations of the effective cation charge (based on the theoretical approach of Kitamura and Chen, 1991) have shown that in the case of transition metals admixed to ZnS and ZnSe there is a contribution of the 3d electrons to the overall charge transfer, which indicates that the ability of 3d electrons to participate in predominantly ionic bond decreases with 3d orbit filling.
5
Content available remote

Chemical Shift of X-Ray K-Absorption Edge of Ni in Some of its Compounds and its Correlation with Partial Charge

100%
Singh V. K., Chetal A. R., Sarode P. R.
Acta Physica Polonica A
|
1995
|
vol. 87
|
issue 6
1003-1008
EN
X-ray absorption Ni K-edge spectra are recorded for the following sys­tems: Ni metal, Ni(NO_{3})_{2} • 6H_{2}0, Ni_{3}(PO_{4})_{2} • 6H_{2}0, NiSO_{4} • 6H_{2}0, NiCO_{3}, NiO and La_{2}NiO_{4} using a Cauchois-type bent crystal spectrograph. The chemical shift of these systems is correlated with the partial charge deter­mined using Sanderson's method. On the basis of regression analysis a rela­tion ΔE = A_{0} + A_{1}q + A_{2}q^{2} -A_{3}q^{3} + A_{4}q^{4} between the chemical shift, ΔE, and the partial charge, q, has been suggested. The discrepancy in the shift of NiO and La_{2}NiO_{4} has also been discussed.
6
Content available remote

EXAFS Determination of Bond Lengths in Zn_{1-x}Fe_{x}S Ternary Alloys

100%
Iwanowski R. J., Ławniczak-Jabłońska K.
Acta Physica Polonica A
|
1997
|
vol. 91
|
issue 4
797-801
EN
Studies of local atomic structure in the zinc-blende Zn_{1-x}Fe_{x}S (x=0.11-0.50) diluted magnetic semiconductors with the use of the EXAFS technique are reported for the first time. They include the K-edge EXAFS measurements for both cationic elements (Zn, Fe). The experiment was carried out at room temperature in the transmission mode using synchrotron radiation of the DCI storage ring in Orsay, France. A detailed EXAFS analysis for different crystal compositions (x) gave a convincing evidence for a bimodal distribution of the nearest-neighbour interatomic distances in Zn_{1-x}Fe_{x}S within the iron solid-solubility limit. It has also revealed, within the accuracy of this method, constancy of both the nearest-neighbour cation-anion distances (i.e. Zn-S and Fe-S) in the composition range studied.
7
Content available remote

The XANES K-Edge Spectra for HgMnSe and HgFeSe

100%
Kisiel A., Oleszkiewicz J., Goniakowski J., Markowski R., Burattini E., Dalba G., Rocca F.
Acta Physica Polonica A
|
1991
|
vol. 80
|
issue 3
373-376
EN
X-ray absorption near-edge structure for Hg_{1-x}Mn_{x}Se and Hg_{1-x}Fe_{x}Se was studied with the use of synchrotron radiation. The self-consistent, semirelativistic LMTO method within the LD approximation was used to calculate electronic band structure and K-edge spectra of these semimagnetic semiconductors. The theoretical results for X-ray absorption spectra were compared with experimental data.
8
Content available remote

X-Ray Absorption Near Edge Structure Analysis of HgMnSe, HgFeSe and HgTeSe

100%
Burattini E., Kisiel A., Markowski R., Dalba G., Giriat W.
Acta Physica Polonica A
|
1993
|
vol. 83
|
issue 1
107-114
EN
Experimental studies of the Se K X-ray absorption edges have been carried out in HgTe_{0.5}Se_{0.5}, Hg_{0.8}Mn_{0.2}Se and Hg_{0.9}Fe_{0.1}Se. A comparison is made for Hg_{0.5}Mn_{0.5}Se and Hg_{0.5}Fe_{0.5}Se theoretical results obtained by the self-consistent, semi-relativistic LMTO method within the LD approximation. Small differences of Se K edge XANES have been shown for HgTeSe and HgSe in contrary to evident differences for HgMnSe and HgFeSe. This behaviour of the absorption Se K edges is related to significant, hybridized contribution of the 3d and 4s Mn or Fe unoccupied states. The maximal contributions of the hybridized bands of the hypothetic zinc-blende MnSe or FeSe were estimated using the virtual crystal model. These maximal contributions are situated at about 6 eV and 17 eV in zinc-blende MnSe and at -0.8 eV and 5.5 eV in zinc-blende FeSe. For HgFeSe apart from the evidence of the strongly localized resonant donor (empty for low Fe concentrations) the complementary hybridized contribution of Fe 3d empty states also situated around the conduction band minimum should be taken into consideration.
9
Content available remote

A Comparative Study of the Methods of Speciation Using X-ray Absorption Fine Structure

100%
Gaur A., Shrivastava B.
|
EN
Determination of the chemical forms along with the relative quantity of the different species in a given sample, termed as speciation, can be done by analyzing X-ray absorption fine structure spectra. The different methods that can be used for speciation are: principal component analysis, target transformation, methods based on derivative spectra, method based on the relative position of the absorption edge, residual phase analysis, normalized difference absorption edge spectra analysis and linear combination fitting. An attempt has been made to make a comparative study of these different methods of speciation by recording the X-ray absorption fine structure at the copper K-edge in a mixture having cuprous oxide and cupric oxide in a specific ratio. The X-ray absorption fine structure spectra of the two oxides have also been recorded separately and the different characteristic X-ray absorption near edge structure features have been identified and their origins have been discussed. Speciation of the mixture has been done using these different methods and the results obtained have been compared and discussed.
10
Content available remote

Correlation of Nearest Neighbour Distance and Bonding Parameters of Exafs of Some Mn and Co Systems

100%
Singh V., Chetal A.
|
EN
Analysing the EXAFS of several Mn and Co systems, the absorbing atom phase shift α and backscattering amplitude phase shift β are evaluated. It is shown that the parameters α and β vary linearly with the nearest neighbour distance, R, except in the systems CoCl_{2}·6H_{2}O, MnSO_{4}·H_{2}O and MnF_{2}. The nearest neighbour distance, R, in the complicated systems like smaltite and braunite minerals was also determined. The values are close to the crystallographic values.
11
Content available remote

Heating-Induced Conversion of Sr-Contaminated Brushite - EXAFS Data Analysis

100%
Rokita E., Łażewski J., Hermes C., Nolting H.-F.
Acta Physica Polonica A
|
1994
|
vol. 86
|
issue 5
767-770
EN
The extended X-ray absorption fine structure method was applied to determine changes of the coordination parameters of Sr atoms during the thermal conversion of Sr-contaminated brushite into calcium pyrophosphate. The results revealed that the changes of the crystallographic structure induced by heating are correlated with the rearrangement of the Sr environment. It was also confirmed that Sr may be used as a marker of Ca in cases of thermal conversions of orthophosphate groups into pyrophosphate groups.
12
Content available remote

Extended X-Ray Bremsstrahlung Isochromat Fine Structure

63%
Sobczak E.
Acta Physica Polonica A
|
1993
|
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.
13
Content available remote

Computational Method of X-Ray Harmonic Elimination in EXAFS Treating

63%
Ovsjannikov P. M.
Acta Physica Polonica A
|
1994
|
vol. 86
|
issue 5
749-752
EN
The computational method of EXAFS amplitude correction by harmonics elimination and intensity leakage assessment has been worked out. In conventional absorption measurements, the major sources of errors are the transition of harmonics by the monochromator and inevitable leakage of radiation around and (or) through the sample. In this paper we present the method of the effective corrections being based on the measurements of the intensity of X-ray radiation passed through calibrated metal foils both without and together with investigated samples. As the advantage of the method one may emphasise the fact that it does not require any additional data for the investigated samples such as chemical composition, density, table absorption coefficients.
14
Content available remote

Oxygen and Silicon K-EXAFS in SiO_{2}

63%
Nietubyć R.
Acta Physica Polonica A
|
1994
|
vol. 86
|
issue 5
741-748
EN
The aim of this work was to calculate EXAFS (extended X-ray absorption fine structure) profile of the constituent elements for SiO_{2} in β-quartz and in its amorphous form within a single scattering curved waves approximation. This method extends the EXAFS analysis to lower energies than the plane wave approximation. We have used wave functions for free ions and Pendry's procedure for central atom phase shifts calculation. Our results for Si K-EXAFS were consistent with experiment, whereas a significant deviation from experimental results for O K-EXAFS was observed. Similar EXAFS profiles for β-quartz and amorphous SiO_{2} were obtained from calculations.
15
Content available remote

X-Ray Absorption Spectroscopy

63%
Mobilio S.
Acta Physica Polonica A
|
1994
|
vol. 86
|
issue 5
645-661
EN
X-ray absorption spectroscopy, today widely used as a tool for structural investigations, is described. Theoretically it is shown that above an absorption edge the absorption coefficient is well approximated by a sum of terms, each one describing a particular path followed by the photoelectron outgoing from the atom. Such geometrical feature allows to use X-ray absorption spectroscopy for structural investigations. The data analysis procedures are outlined. Applications of the single scattering region, generally known as EXAFS to semiconductors alloys, to metallic clusters and to the crystallization of amorphous metallic glasses are illustrated. Multiple scattering calculations and their relation to experimental spectra is discussed in the case of Mn ions in solution. Application of the multiple scattering to determine the three-body correlation function in a-Si:H is shown.
16
Content available remote

Application of EXAFS to Catalysis and Surface Science

63%
Renouprez A. J.
Acta Physica Polonica A
|
1994
|
vol. 86
|
issue 5
663-674
EN
The paper gives recent applications of EXAFS to the structural study of microcrystalline bimetallic particles. Special attention has been paid to the case of systems composed of neighbouring elements. Also it is shown how the use of X-ray diffraction techniques and surface science methods like ion scattering can be indispensable to interpret the EXAFS data correctly. In catalysis and surface science, experiments performed in total reflection mode can provide a detailed description of the adsorption site of atoms on a flat surface.
17
Content available remote

Comparison between Mo BIS and Mo K-Edge Absorption Spectrum

63%
Sobczak E.
Acta Physica Polonica A
|
1992
|
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}.
18
Content available remote

Extended Structure of Fe BIS as Compared to Fe K EXAFS

63%
Sobczak E., Mobilio S.
Acta Physica Polonica A
|
1992
|
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.
19
Content available remote

Interpretation of Differential Anomalous X-Ray Scattering Data for Amorphous Cd-As

63%
Burian A., Lecante P., Mosset A., Galy J., Tonnerre J. M., Raoux D.
Acta Physica Polonica A
|
1994
|
vol. 86
|
issue 4
633-640
EN
The computational procedure, based on Warren's exact method for an amorphous sample with more than one atom, was developed to obtain the short-range order structural parameters from the differential anomalous X-ray scattering data, collected using the synchrotron radiation. The experimental differential radial distribution functions were fitted with the true distribution functions expressed in an analytical form and broadened by convolution with the pair functions. It was found that atoms in the amorphous Cd-As films remain almost tetrahedrally coordinated and the investigated alloys are chemically ordered.
20
Content available remote

Surface X-Ray Absorption Spectroscopy: Basic Concepts and Applications

63%
Lagarde P.
Acta Physica Polonica A
|
1997
|
vol. 91
|
issue 4
641-647
EN
The application to surface problems of X-ray spectroscopy has started almost at the same time as in materials science. While the theoretical basis is obviously the same, SEXAFS has some experimental peculiarities which are reviewed here. Some examples will then be given.
first rewind previous Page / 2 next fast forward last
JavaScript is turned off in your web browser. Turn it on to take full advantage of this site, then refresh the page.