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Tytuł:
L$\text{}_{1}$ Absorption Edge of the 4f Heavy Rare-Earth Metals
Autorzy:
Shrivastava, B. D.
Joshi, S. K.
Powiązania:
https://bibliotekanauki.pl/articles/1920520.pdf
Data publikacji:
1992-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Dm
Opis:
The wavelengths of the L$\text{}_{1}$ absorption edges of the 4f heavy rare-earth metals ($\text{}^{65}$Tb to $\text{}^{71}$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$\text{}_{1}$ edges of the rare earths in metallic form and its occurrence in their compounds has been discussed.
Źródło:
Acta Physica Polonica A; 1992, 81, 3; 385-392
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Heating-Induced Conversion of Sr-Contaminated Brushite - EXAFS Data Analysis
Autorzy:
Rokita, E.
Łażewski, J.
Hermes, C.
Nolting, H.-F.
Powiązania:
https://bibliotekanauki.pl/articles/1931728.pdf
Data publikacji:
1994-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Dm
Opis:
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.
Źródło:
Acta Physica Polonica A; 1994, 86, 5; 767-770
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Chemical Shift of X-Ray K-Absorption Edge of Ni in Some of its Compounds and its Correlation with Partial Charge
Autorzy:
Singh, V. K.
Chetal, A. R.
Sarode, P. R.
Powiązania:
https://bibliotekanauki.pl/articles/1933455.pdf
Data publikacji:
1995-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Dm
Opis:
X-ray absorption Ni K-edge spectra are recorded for the following systems: Ni metal, Ni(NO$\text{}_{3}$)$\text{}_{2}$ • 6H$\text{}_{2}$0, Ni$\text{}_{3}$(PO$\text{}_{4}$)$\text{}_{2}$ • 6H$\text{}_{2}$0, NiSO$\text{}_{4}$ • 6H$\text{}_{2}$0, NiCO$\text{}_{3}$, NiO and La$\text{}_{2}$NiO$\text{}_{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$\text{}_{0}$ + A$\text{}_{1}$q + A$\text{}_{2}$q$\text{}^{2}$ -A$\text{}_{3}$q$\text{}^{3}$ + A$\text{}_{4}$q$\text{}^{4}$ between the chemical shift, ΔE, and the partial charge, q, has been suggested. The discrepancy in the shift of NiO and La$\text{}_{2}$NiO$\text{}_{4}$ has also been discussed.
Źródło:
Acta Physica Polonica A; 1995, 87, 6; 1003-1008
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The XANES K-Edge Spectra for HgMnSe and HgFeSe
Autorzy:
Kisiel, A.
Oleszkiewicz, J.
Goniakowski, J.
Markowski, R.
Burattini, E.
Dalba, G.
Rocca, F.
Powiązania:
https://bibliotekanauki.pl/articles/1890922.pdf
Data publikacji:
1991-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Dm
Opis:
X-ray absorption near-edge structure for Hg$\text{}_{1-x}$Mn$\text{}_{x}$Se and Hg$\text{}_{1-x}$Fe$\text{}_{x}$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.
Źródło:
Acta Physica Polonica A; 1991, 80, 3; 373-376
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Amorphous Bi-Ge-S(Se) Systems Studied by X-Ray Ge K Emission and Absorption Bands
Autorzy:
Drahokoupil, J.
Drbohlav, I.
Polčik, M.
Tichý, L.
Powiązania:
https://bibliotekanauki.pl/articles/1931701.pdf
Data publikacji:
1994-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Dm
Opis:
The X-ray Ge K absorption (emission) bands were measured in the stoichiometric glass system (GeS$\text{}_{2}$)$\text{}_{x}$(Bi$\text{}_{2}$S$\text{}_{3}$)$\text{}_{1-x}$ (x = 0 ÷ 0.5) and in the Ge$\text{}_{20}$Bi$\text{}_{y}$Se$\text{}_{80-y}$ system (y = 0, 7 and 13). The results do not confirm the existence of the Ge-Bi bond and they imply that the GeS$\text{}_{2}$-clusters are formed in both studied systems.
Źródło:
Acta Physica Polonica A; 1994, 86, 5; 721-726
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
X-Ray Absorption Near Edge Structure Analysis of HgMnSe, HgFeSe and HgTeSe
Autorzy:
Burattini, E.
Kisiel, A.
Markowski, R.
Dalba, G.
Giriat, W.
Powiązania:
https://bibliotekanauki.pl/articles/1924330.pdf
Data publikacji:
1993-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Dm
Opis:
Experimental studies of the Se K X-ray absorption edges have been carried out in HgTe$\text{}_{0.5}$Se$\text{}_{0.5}$, Hg$\text{}_{0.8}$Mn$\text{}_{0.2}$Se and Hg$\text{}_{0.9}$Fe$\text{}_{0.1}$Se. A comparison is made for Hg$\text{}_{0.5}$Mn$\text{}_{0.5}$Se and Hg$\text{}_{0.5}$Fe$\text{}_{0.5}$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.
Źródło:
Acta Physica Polonica A; 1993, 83, 1; 107-114
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Comparative Study of the Methods of Speciation Using X-ray Absorption Fine Structure
Autorzy:
Gaur, A.
Shrivastava, B.
Powiązania:
https://bibliotekanauki.pl/articles/1489872.pdf
Data publikacji:
2012-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Dm
Opis:
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.
Źródło:
Acta Physica Polonica A; 2012, 121, 3; 647-652
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Correlation of Nearest Neighbour Distance and Bonding Parameters of Exafs of Some Mn and Co Systems
Autorzy:
Singh, V. K.
Chetal, A. R.
Powiązania:
https://bibliotekanauki.pl/articles/1968861.pdf
Data publikacji:
1998-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Dm
Opis:
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$\text{}_{2}$·6H$\text{}_{2}$O, MnSO$\text{}_{4}$·H$\text{}_{2}$O and MnF$\text{}_{2}$. 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.
Źródło:
Acta Physica Polonica A; 1998, 93, 3; 523-526
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
EXAFS Determination of Bond Lengths in Zn$\text{}_{1-x}$Fe$\text{}_{x}$S Ternary Alloys
Autorzy:
Iwanowski, R. J.
Ławniczak-Jabłońska, K.
Powiązania:
https://bibliotekanauki.pl/articles/1963384.pdf
Data publikacji:
1997-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Dm
Opis:
Studies of local atomic structure in the zinc-blende Zn$\text{}_{1-x}$Fe$\text{}_{x}$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$\text{}_{1-x}$Fe$\text{}_{x}$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.
Źródło:
Acta Physica Polonica A; 1997, 91, 4; 797-801
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Chemical Shifts at K-Absorption Edges of Transition Metals Admixed To ZnS and ZnSe
Autorzy:
Iwanowski, R. J.
Ławniczak-Jabłońska, K.
Traverse, A.
Powiązania:
https://bibliotekanauki.pl/articles/1963385.pdf
Data publikacji:
1997-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Dm
Opis:
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$\text{}_{1-x}$M$\text{}_{x}$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.
Źródło:
Acta Physica Polonica A; 1997, 91, 4; 803-808
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Determination by X-Ray Absorption of Redox Induced Structural Changes in Iron-Sulfur Cluster F$\text{}_{x}$ in Photosystem I
Autorzy:
Sagi, I.
Bunker, G.
Hochman, Y.
Carmeli, C.
Zeng, M. T.
Powiązania:
https://bibliotekanauki.pl/articles/1963399.pdf
Data publikacji:
1997-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Dm
Opis:
X-ray absorption spectra of photosystem I core protein containing F$\text{}_{x}$, 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$\text{}_{x}$. 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$\text{}_{x}$ are interpreted to indicate structural changes of the iron-sulfur cluster in F$\text{}_{x}$ upon reduction.
Źródło:
Acta Physica Polonica A; 1997, 91, 5; 871-875
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Femtosecond X-ray Absorption Spectroscopy οf a Light-Driven Spin-Crossover Process
Autorzy:
Milne, C.
Pham, V.
Gawelda, W.
Nahhas, A.
van der Veen, R.
Johnson, S.
Beaud, P.
Ingold, G.
Borca, C.
Grolimund, D.
Abela, R.
Chergui, M.
Bressler, Ch.
Powiązania:
https://bibliotekanauki.pl/articles/1539083.pdf
Data publikacji:
2010-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Dm
75.30.Wx
Opis:
Understanding the initial steps during ultrafast molecular reactions involving large spin state changes is a vital goal in structural dynamics research. These involve knowledge of the geometric structure of the system. Ultrafast X-ray absorption spectroscopy with 50-100 picosecond time resolution establishes the geometric structure of the short-lived (τ = 0.6 ns) high spin state. Here we focus on time-resolved X-ray absorption studies with 160-200 fs temporal resolution to monitor the structural evolution in this spin-conversion process.
Źródło:
Acta Physica Polonica A; 2010, 117, 2; 391-393
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Comparison between Mo BIS and Mo K-Edge Absorption Spectrum
Autorzy:
Sobczak, E.
Powiązania:
https://bibliotekanauki.pl/articles/1920907.pdf
Data publikacji:
1992-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
79.20.Kz
78.70.Dm
Opis:
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$\text{}^{-1}$ 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$\text{}^{-1}$ and by beating effect at 3.7 Å$\text{}^{-1}$ 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$\text{}^{-1}$.
Źródło:
Acta Physica Polonica A; 1992, 82, 2; 329-332
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Oxygen and Silicon K-EXAFS in SiO$\text{}_{2}$
Autorzy:
Nietubyć, R.
Powiązania:
https://bibliotekanauki.pl/articles/1931716.pdf
Data publikacji:
1994-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.10.Wg
78.70.Dm
Opis:
The aim of this work was to calculate EXAFS (extended X-ray absorption fine structure) profile of the constituent elements for SiO$\text{}_{2}$ 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$\text{}_{2}$ were obtained from calculations.
Źródło:
Acta Physica Polonica A; 1994, 86, 5; 741-748
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Computational Method of X-Ray Harmonic Elimination in EXAFS Treating
Autorzy:
Ovsjannikov, Ph. M.
Powiązania:
https://bibliotekanauki.pl/articles/1931720.pdf
Data publikacji:
1994-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
87.64.Fb
78.70.Dm
Opis:
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.
Źródło:
Acta Physica Polonica A; 1994, 86, 5; 749-752
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł

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