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Wyświetlanie 1-15 z 22
Tytuł:
Asymmetry in Mössbauer spectra of FeIII-azaporphyrin complexes
Autorzy:
Kaczmarzyk, T.
Jackowski, T.
Dziliński, K.
Sinyakov, G.
Powiązania:
https://bibliotekanauki.pl/articles/148331.pdf
Data publikacji:
2007
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
Mössbauer spectroscopy
iron porphyrins
azaporphyrins
asymmetry in Mössbauer spectra
spin-spin and spin-lattice relaxation
Opis:
Temperature dependence of asymmetry as well as isomer shift and quadrupole splitting values of Mössbauer spectra of trivalent iron complexes coordinated to porphyrin ligands such as octaethylporphyrin, monoazaethioporphyrin, diazaoctaethylporphyrin and phthalacyanine is discussed in this paper. All the above mentioned complexes have the chloride axial ligand at the fifth coordination site. Different temperature changes of asymmetry and other parameters of Mössbauer spectra of these complexes can be correlated with a number of methine bridges CH substituted by nitrogen atoms in the porphyrin macrocycle. The form of this asymmetry is such that the higher-energy component of the doublet is more broadened than the lower-energy one, while the areas (intensities) under each of two components are the same. The most distinct asymmetry is observed at room temperature. When temperature is decreasing, the spectrum becomes successively more symmetrical and at liquid helium temperature linewidths of both components of the quadrupole splitting are very close one another. The Mössbauer spectrum of the FeCl-monoazaethioporphyrin complex exhibits reversed asymmetry at liquid helium temperature in comparison with the spectra of the remaining complexes i.e. the lower-energy component of the doublet is slightly more broadened than the higher-energy one. The spin-spin and spinlattice relaxation mechanisms in the context of quantum mechanically mixed spin states S = 5/2 + 3/2 of FeIII ions are considered as a source of the observed asymmetry.
Źródło:
Nukleonika; 2007, 52, supl. 1; 93-98
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Search for canted spin arrangement in Er2-xTbxFe14B with Mössbauer spectroscopy
Autorzy:
Kurzydło, P. M.
Bogacz, B. F.
Pędziwiatr, A. T.
Oleszak, D.
Przewoźnik, J.
Powiązania:
https://bibliotekanauki.pl/articles/147036.pdf
Data publikacji:
2015
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
Mössbauer effect
permanent magnet materials
spin diagrams
spin reorientation
Opis:
The materials studied were polycrystalline compounds Er2-xTbxFe14B (x = 0.1, 0.2, 0.3, 0.4) which crystallize in a tetragonal lattice and display a variety of spin arrangements. The compounds have been measured with 57Fe Mössbauer spectroscopy over the temperature range 80–320 K in order to investigate the spin reorientation processes. Each compound was studied in a wide temperature range, with precise Mössbauer scanning in the vicinity of the transition. The set of spectra obtained for a given compound was analyzed using simultaneous fi tting procedure to investigate the infl uence of the transition on the shape of the spectra. The fi tting program was specifi ed to analyze the transition according to the ‘two state model’: spins fl ip abruptly from initial angle to fi nal arrangement (90° angle). Obtained results suggest that spin reorientation process cannot be described using only the mentioned above model. Additional computer simulations based on the Yamada–Kato model were conducted to determine temperature range and the type of spin alignments in the vicinity of the transition. These theoretical results supported by spectra analysis suggest the existence of intermediate (canted) spin arrangements in the studied compounds. The spin arrangement diagram was constructed.
Źródło:
Nukleonika; 2015, 60, 1; 93-96
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spin reorientation process in Tm2–xHoxFe14B : analysis of conical arrangement based on Mössbauer spectra
Autorzy:
Kurzydło, P. M.
Pędziwiatr, A. T.
Bogacz, B. F.
Przewoźnik, J.
Oleszak, D.
Powiązania:
https://bibliotekanauki.pl/articles/148120.pdf
Data publikacji:
2017
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
permanent magnetic materials
Mössbauer effect
spin reorientation
spin diagrams
Opis:
The spin reorientation process in the Tm2–xHoxFe14B series of compounds was studied using 57Fe Mössbauer spectroscopy over the temperature range 5.2–320 K with a focus on the analysis of conical spin arrangement. Each compound was studied by precise Mössbauer scanning in the vicinity of the transition and during the transition. By applying computer simulations based on the simplified Yamada-Kato model, as well as on some literature data for R2Fe14B (R = Tm, Ho) compounds, the above series was selected for studies as it contains compounds with different spin arrangements (axial, planar, conical). It was a crucial requirement for obtaining unambiguous angular dependences when applying a simultaneous fitting procedure of Mössbauer spectra. Such an extended procedure was applied which allowed the temperature dependence of the angle describing the position of the magnetization vector to be obtained. The results were compared with those from theoretical simulations. The spin arrangement diagram was constructed. A conical spin arrangement was confirmed over a wide temperature range.
Źródło:
Nukleonika; 2017, 62, 2; 123-127
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spin arrangement diagrams for Er2-xRxFe14B (R = Y, Ce) obtained with Mössbauer spectroscopy and phenomenological model
Autorzy:
Pędziwiatr, A.
Bogacz, B.
Gargula, R.
Powiązania:
https://bibliotekanauki.pl/articles/148797.pdf
Data publikacji:
2003
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
Mössbauer effect
permanent magnet materials
spin diagrams
spin reorientation
Opis:
Two isostructural series of polycrystalline compounds: Er2-xYxFe14B and Er2-xCexFe14B have been studied by 57Fe Mössbauer spectroscopy in the temperature range 80-370 K. The spin reorientation phenomenon (a transition from basal plane to axial easy magnetisation direction) has been studied extensively by a narrow step temperature scanning in the vicinity of the transition. Using the procedure of subtracting the Mössbauer spectra taken for the same compound at different temperatures, it was possible to follow the influence of transition on the shape of spectra. From this procedure it was concluded that in the region of transition each subspectrum splits into two Zeeman sextets, which are characterised by different hyperfine magnetic fields and quadrupole splittings. The consistent way of describing the Mössbauer spectra was proposed. The spin reorientation temperatures have been established for all compositions and compared with the values obtained from theoretical calculations of spin orientation angle based on phenomenological model. The spin arrangement diagrams have been constructed.
Źródło:
Nukleonika; 2003, 48,suppl.1; 59-63
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mössbauer studies of spin reorientations in Er2-xGdxFe14B
Autorzy:
Wojciechowska, A.
Bogacz, B.
Pędziwiatr, A.
Powiązania:
https://bibliotekanauki.pl/articles/147233.pdf
Data publikacji:
2004
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
Mössbauer effect
spin reorientation
Opis:
The Er2 xGdxFe14B (x = 0.5, 1.0, 1.5) polycrystalline compounds have been investigated with 57Fe Mössbauer spectroscopy in the 80 330 K temperature range. The spin reorientation phenomena (changes from planar to axial spin arrangements) have been studied extensively by a narrow step temperature scanning in the neighbourhood of the spin reorientation temperature. From the analysis of the spectra it was deduced that in the region of transition each subspectrum was split into two Zeeman sextets, which were characterized by different hyperfine magnetic fields and quadrupole splittings. A consistent way of describing the Mössbauer spectra in the wide range of temperatures was proposed. The composition and temperature dependencies of hyperfine interaction parameters and subspectra contributions were derived from experimental spectra. The transition temperatures were determined for all the compounds studied.
Źródło:
Nukleonika; 2004, 49,suppl.3; 71-73
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spin reorientation phenomena in Er2-xRxFe14B (R = Gd, Th) – Mössbauer and calorimetric study
Autorzy:
Wojciechowska, A.
Pędziwiatr, A.
Bogacz, B.
Wróbel, S.
Powiązania:
https://bibliotekanauki.pl/articles/148335.pdf
Data publikacji:
2007
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
Mössbauer effect
spin reorientation
Opis:
The Er2 xGdxFe14B (x = 0.5, 1.0, 1.5) and Er2 xThxFe14B (x = 0.0, 0.5, 1.0, 1.5, 2.0) polycrystalline compounds have been investigated with 57Fe Mössbauer spectroscopy and differential scanning calorimetry (DSC). A comparison of results related to spin reorientation phenomena obtained for Gd- and Th-substituted compounds is presented in this paper. Spin reorientation phenomena (changes from planar to axial spin arrangements) have been studied extensively by a narrow step temperature scanning in the neighbourhood of the spin reorientation temperature, TSR. From the analysis of Mössbauer spectra, it was deduced that in the region of transition each subspectrum was split into two Zeeman sextets, which were characterised by different hyperfine magnetic fields and quadrupole splittings. A consistent way of fitting the spectra in the wide range of temperatures was proposed. The composition and temperature dependencies of hyperfine interaction parameters and subspectra contributions were derived from fits and the transition temperatures were determined for all the compounds studied. DSC studies proved that the spin reorientations were accompanied by thermal effects for all compositions of the Gd- and for x = 0.5 of the Th-series. Transformation enthalpy and TSR were determined from these studies and the two-stage character of transition was confirmed. Magnetic spin arrangement diagrams for R = Th and Gd series were constructed and compared using combined data obtained with both methods.
Źródło:
Nukleonika; 2007, 52, supl. 1; 77-79
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Antioxidant properties of wines produced in the Podkarpacie region
Autorzy:
Szterk, A.
Stefaniuk, I.
Cieniek, B.
Kuźma, M.
Powiązania:
https://bibliotekanauki.pl/articles/147112.pdf
Data publikacji:
2013
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
electron spin resonance (ESR)
POBN spin trap
superoxide radial anion
Polish wines
Opis:
The wine is famous and popular drink having properties of reactive oxygen species scavenging. In this paper we study the antioxidant activity of the selected wines produced in the south-east region of Poland, in Subcarpathian Voivodeship, in the Podkarpacie region. We have concentrated our studies on the superoxide radical anion O2 •–. We have used electron spin resonance spectroscopy (ESR) as it is the best method for radical detection. The nitrone spin trap α-(4-pyridyl-1-oxide)-N-tert-butylnitrone (POBN) has been used in the experiment. The radical scavenging ability of wines were determined from the changing intensity of the spectrum in time.
Źródło:
Nukleonika; 2013, 58, 3; 447-450
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Correlation femtoscopy
Autorzy:
Lednický, R.
Powiązania:
https://bibliotekanauki.pl/articles/147326.pdf
Data publikacji:
2004
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
particle
emission
correlations
spin
flow
delay
interaction
Opis:
Recent results on particle momentum and spin correlations are discussed, particularly, in view of the role played by the effect of final state interaction. It is demonstrated that this effect allows for (i) correlation femtoscopy with unlike particles; (ii) study of the relative space-time asymmetries in the production of different particle species (e.g., relative time delays or spatial shifts due to collective flows); (iii) study of the particle strong interaction hardly accessible by other means (e.g., in logical and logical and system).
Źródło:
Nukleonika; 2004, 49,suppl.2; 3-6
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spin trapping studies of essential oils in lipid systems
Autorzy:
Makarova, K.
Drązikowska, K.
Suska, B.
Zawada, K.
Wawer, I.
Powiązania:
https://bibliotekanauki.pl/articles/147786.pdf
Data publikacji:
2015
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
spin trapping ESR
essential oils
DFT calculations
lipids
Opis:
In the present work, we report the results of a spin trapping ESR study of four essential oils widely used for skin care products such as creams and bath salts. The studied essential oils are Rosmarini aetheroleum (rosemary), Menthae piperitae aetheroleum (mint), Lavandulae aetheroleum (lavender), and Thymi aetheroleum (thyme). Fenton reaction in the presence of ethanol was used to generate free radicals. The N-tert- -butyl-α-phenylnitrone (PBN) was used as a spin trap. In the Fenton reaction, the rosemary oil had the lowest effect on radical adduct formation as compared to the reference Fenton system. Since essential oils are known to be lipid soluble, we also conducted studies of essential oils in Fenton reaction in the presence of lipids. Two model lipids were used, namely 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1,2-dipalmitoyl-sn- -glycero-3-phosphocholine (DPPC). The obtained results suggested that in the presence of DOPC lipids, the •OH and PBN/•CHCH3(OH) radicals are formed in both phases, that is, water and lipids, and all the studied essential oils affected the Fenton reaction in a similar way. Whereas, in the DPPC system, the additional type of PBN/X (aN = 16.1 G, aH = 2.9 G) radical adduct was generated. DFT calculations of hyperfi ne splittings were performed at B3LYP/6-311+G(d,p)/EPR-II level of theory for the set of c-centered PBN adducts in order to identify PBN/X radical.
Źródło:
Nukleonika; 2015, 60, No. 3, part 1; 461-468
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigation of the level structure of 90Nb nucleus using the shell model
Autorzy:
Yi-Heng, Wu
Dong, Yang
Ke-Yan, Ma
Peng-Wei, Luo
Powiązania:
https://bibliotekanauki.pl/articles/147040.pdf
Data publikacji:
2019
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
high spin state
level structure
proton excitation
shell model
Opis:
Shell model calculations have been carried out for 90Nb nucleus with the model space in which the valence protons occupy the f5/2, p3/2, p1/2, and g9/2 orbitals and the valence neutrons occupy the p1/2, g9/2, d5/2, and g7/2 orbitals. According to the calculated results, the negative parity is from the contribution of the proton of the f5/2, p3/2, and p1/2 orbits. The moderate spin states of 90Nb are mainly due to the excitation of protons from the f5/2 and p3/2 orbits to the p1/2 and g9/2 orbits across the Z = 38 subshell closure, and the high spin states arise from the excitation of a single neutron from the g9/2 orbit into the d5/2 orbit across the N = 50 shell closure.
Źródło:
Nukleonika; 2019, 64, 4; 113-116
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of nitrogen substitution in porphyrin ring on Mössbauer parameters of iron ions
Autorzy:
Kaczmarzyk, T.
Jackowski, T.
Dziliński, K.
Sinyakov, G.
Powiązania:
https://bibliotekanauki.pl/articles/147210.pdf
Data publikacji:
2004
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
Mössbauer spectroscopy
iron porphyrins
azaporphyrins
trivalent-iron spin states
Opis:
Electron configuration changes of Fe(III) ions in porphyrin complexes with chloride axial ligands caused by the successive nitrogen substitution of CH methine bridges at meso positions of the porphyrin ring is discussed on the basis of Mössbauer spectroscopy results. It was shown that increase of a number of nitrogen atoms at the meso positions changes the character of quantum-mechanically mixed spin state of Fe(III) ions (S = 5/2 + 3/2) by the increase of the intermediate-spin (S = 3/2) contribution. This feature is reflected in Mössbauer spectra by an increase of quadrupole splitting values and the decrease of the asymmetry of quadrupole doublets, when the number of nitrogen atoms at the meso positions increases. Isomer shifts remain practically unchanged. These peculiarities are discussed in the light of spin relaxation mechanisms and the occupancy of d orbitals in Fe(III) ions coordinated to the porphyrin ring and chloride ligand. It has been noticed that Mössbauer parameters correlate qualitatively with EPR data.
Źródło:
Nukleonika; 2004, 49,suppl.3; 13-16
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Charge and spin density perturbation on iron atom due to osmium impurity in metallic iron
Autorzy:
Błachowski, A.
Ruebenbauer, K.
Żukrowski, J.
Powiązania:
https://bibliotekanauki.pl/articles/147245.pdf
Data publikacji:
2004
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
Mössbauer spectroscopy
charge and spin density
impurities in metal
Opis:
Samples of natural alfa-Fe doped randomly with Os impurities up to about 9 at.% have been investigated by means of the 14.41 keV Mössbauer absorption spectroscopy of 57Fe vs. Os concentration and at room temperature. It has been found that the nearest neighbor single Os impurity reduces hyperfine magnetic field on the iron nucleus by 3.97 T, while the second neighbor single Os impurity decreases this field by 1.11 T. More distant impurities slightly increase iron hyperfine field. There are no discernible effects of the Os-Os interaction on the magnetic field seen by iron. On the other hand, the electron charge density on the iron nucleus is increased by the nearest neighbor Os atom as seen via changes in the isomer shift, i.e. via changes in the spectral shift. The second neighbor impurity has the opposite effect on the charge density. More distant impurities tend to decrease the charge density as well. The effect of the first and second neighbor impurities decreases with increasing overall Os concentration indicating some Os-Os interaction influencing a charge density of the conduction electrons seen on the iron nucleus.
Źródło:
Nukleonika; 2004, 49,suppl.3; 67-70
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
EMR study and superposition model analysis of Cr3+ and Fe3+ impurity ions in mullite powders used in aerospace industry
Autorzy:
Stefaniuk, I.
Rogalska, I..
Powiązania:
https://bibliotekanauki.pl/articles/146307.pdf
Data publikacji:
2015
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
electron magnetic resonance (EMR)
mullites
spin Hamiltonian (SH)
superposition model (SPM)
Opis:
In this work, the electron magnetic resonance (EMR) spectra of the mullites powders were measured for different grain sizes (0.07 and 0.12 mm). We have used EMR spectroscopy at X-band, combined with superposition model (SPM) calculations to reveal electronic structure and establish correlations between structure, and surroundings of these complexes.
Źródło:
Nukleonika; 2015, 60, No. 3, part 1; 399-403
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Computer program superposition model - Monte Carlo (SPM-MC) and its applications in EMR studies of transition ions at low symmetry sites Fe3+ doped YAP crystals
Autorzy:
Stefaniuk, I.
Rudowicz, Cz.
Powiązania:
https://bibliotekanauki.pl/articles/146564.pdf
Data publikacji:
2013
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
superposition model (SPM)
spin Hamiltonian (SH)
yttrium aluminum perovskite (YAP)
YAlO3
Opis:
An extension of the computer program superposition model-Monte Carlo (SPM-MC), designed for modelling of the spectroscopic and structural properties of transition ions at low symmetry sites in crystals, is presented. Special focus is put on two aspects. The first aspect concerns the effects of variation of the superposition model (SPM) parameters, i.e. the intrinsic parameters (b2, b4) and power low exponents (t2, t4), on the quality of fittings of experimental data and theoretical predictions. This enables to increase the reliability of the modelling results. The second aspect concerns the implications of low site symmetry on modelling of the pertinent properties. Applications of the program SPM-MC to Fe3+ ions at the triclinic (Ci) symmetry sites in YAlO3 (YAP) crystals are considered.
Źródło:
Nukleonika; 2013, 58, 3; 397-400
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The influence of selected amino acids on the dynamic properties of the liposome membranes : ESR study
Autorzy:
Man, D.
Broda, M.
Buczek, A.
Kawecka, A.
Siodłak, D.
Powiązania:
https://bibliotekanauki.pl/articles/146690.pdf
Data publikacji:
2013
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
EYL liposomes
electron spin resonance (ESR) method
N-methylation
amino acids
peptides
Opis:
In this work the changes in the fluidity of liposome membranes caused by alanine and butyrine derivatives (Ac-Ala-NMe2 and Ac-Abu-NMe2) were investigated. Liposomes were obtained in the process of egg yolk lecithin (EYL) sonication. The concentration of the admixture in the proportion to EYL varied from 0 to 25% mole. The electron spin resonance (ESR) spectroscopy was used with two different spins probes. Each spin probe penetrates different regions of liposome membrane. The TEMPO probe occurs both in the hydrophobic part of the membrane and in the water environment what allows to determine the spectroscopic parameter F of division of this probe into the membrane and its water surrounding. DOXYL is localized in the central part of the lipid bilayer and is used to obtain the spectroscopic parameter τ – rotation correlation time – whose value gives information about fluidity changes in the middle of the lipid bilayer. The study indicated that the tested as admixtures N-methylated model peptides significantly changed the fluidity of liposome membranes. The dynamic of this process depends both on amino acids derivative and on the membrane region. Both studied compounds increased the fluidity of the surface layer of liposome membrane. At the same time, butyrine derivative caused the stiffening of the middle part of liposome bilayer, but alanine derivative slightly increased the fluidity of this region.
Źródło:
Nukleonika; 2013, 58, 3; 443-446
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 22

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