REDUCTION BY HYDROGEN OF VANADIUM IN PHOSPHATE AND VANADATE LEAD APATITES: AN ESR STUDY

2007 ◽  
Vol 21 (22) ◽  
pp. 1489-1500 ◽  
Author(s):  
M. IKRAM ◽  
H. AHMED ◽  
PIETRO MENDES ◽  
F. A. MIR ◽  
A. BASHIR ◽  
...  
Keyword(s):  
Solid Solution ◽  
Computer Simulations ◽  
Esr Spectroscopy ◽  
Esr Spectra ◽  
Hydrogen Gas ◽  
Charge Carriers ◽  
Spin Hamiltonian ◽  
Powder Spectrum ◽  
Hamiltonian Parameters ◽  
Vanadium Ions

A solid solution of phosphate and vanadate lead apatites Pb 10( PO 4)6-x( VO 4)x( OH )2 (x = 0.5, 1.0, 2.0, 3.0, and 6.0) were reduced with hydrogen gas at temperature 300°C for one hour. All these compounds were investigated by XRD and ESR spectroscopy. Only one reduced oxidation state, V 4+, was detected. Two types of species-like isolated vanadium (+ 4) and clusters of V 4+ were observed. The EPR powder spectrum computer simulations were performed using the program Simfonia from Bruker. Spin Hamiltonian parameters were also calculated. As the concentrations of vanadium ions increase to 2.0, the intensity of the ESR lines increases, and x = 3.0 the intensity of the ESR line decreases sharply. After this concentration, i.e. x > 3.0, there is again an increase in the intensity. The variation of the line shape and intensity of the ESR spectra can be attributed to increases in the hopping rate of the charge carriers (polarons) in different apatite compositions.

ESR STUDY OF SPIN-HAMILTONIAN PARAMETERS AND CRYSTAL FIELD ENERGY LEVELS FOR THE LOW C3 SYMMETRY Fe3+ CENTER IN GREEN SAPPHIRE CRYSTALS AND POWDER

2007 ◽  
Vol 21 (04) ◽  
pp. 225-236 ◽  
Author(s):  
P. LIMSUWAN ◽  
N. UDOMKAN ◽  
P. WINOTAI
Keyword(s):  
Rotation Angle ◽  
Energy Levels ◽  
Heat Treating ◽  
Esr Spectra ◽  
Field Energy ◽  
Hamiltonian Matrix ◽  
Magnetic Field Direction ◽  
Spin Hamiltonian ◽  
Corundum Structure ◽  
Hamiltonian Parameters

In this report, Fe 3+ impurity ions present in green sapphire ( Al 2 O 3) were studied experimentally, by heating a light green sapphire in flowing oxygen atmosphere for 12 h from 1200, 1300, 1400, 1500 and 1600°C, respectively. Electron spin resonance (ESR) spectra in X-band (~9.45 GHz ) were recorded by mounting the crystal with the c-axis perpendicular (θ = 90°) to the magnetic field direction. The spectra were recorded and simulated by a numerical diagonalization of spin Hamiltonian matrix in the range from 0 to 180 degrees for every 15 degrees of rotation angle (φ). In our case, only the last two sets of peaks strongly depend on the rotation angle (φ), and each exhibits C 3 symmetry due to two magnetically inequivalent Fe 3+ sites in the corundum structure. For polycrystalline ESR spectra, seven main Fe 3+ ESR absorption peaks occur at the resonance magnetic fields of 100.20, 310.24, 486.80, 525.00, 550.60, 761.00 and 777.00 mT respectively. Specifically, ESR signals show that the number of paramagnetic Fe 3+ ions increase roughly linearly with the heat treating temperature, having the [Formula: see text] ratio ~1.41 at 1600°C.

ESR Spectra of Charge Carriers in the α'- and β- Phases of (BEDT-TTF)2IBr2 Single Crystals

2012 ◽  
Vol 190 ◽  
pp. 615-618 ◽  
Author(s):  
A. Chernenkaya ◽  
A.I. Dmitriev ◽  
M. Kirman ◽  
O.V. Koplak ◽  
R.B. Morgunov
Keyword(s):  
Magnetic Moment ◽  
High Frequency ◽  
Esr Spectroscopy ◽  
Esr Spectra ◽  
Organic Conductors ◽  
Charge Carriers ◽  
Localized States ◽  
Two Dimensional ◽  
Orbital Magnetic Moment ◽  
Spin Resonance

High-frequency dynamic magnetic properties of quasi-two-dimensional organic conductors (BEDT-TTF)2IBr2ofα'- andβ-phases have been studied by Electron Spin Resonance (ESR) spectroscopy. The heating of crystals in theα'-phase is accompanied by their phase transition to theβ-phase, so, the Dyson distortion of the ESR line is appeared. Contributions from the crystal field and symmetry of the system as well as the orbital magnetic moment admixture to the total magnetic moment of charge carriers have been judged by the comparison of the orientation and temperature dependencies of the ESR spectra for theα'- andβ-phases. Experimental data have proved localized states of charge carriers either inα'- orβ-phases.

ELECTRON PARAMAGNETIC RESONANCE STUDIES OF (VO4)+2 IONS DOPED IN REDUCED Pb10-xCax(VO4)1(PO4)5(OH)2 APATITES [x = 0.0, 2.0, 4.0, 6.0, 8.0, AND 10.0]

2009 ◽  
Vol 23 (16) ◽  
pp. 3369-3389
Author(s):  
M. IKRAM ◽  
R. AMBARDAR ◽  
A. M. ROSSI ◽  
J. G. EON
Keyword(s):  
Esr Spectroscopy ◽  
Lattice Relaxation ◽  
Esr Spectra ◽  
Hydrogen Gas ◽  
Spin Lattice Relaxation ◽  
Paramagnetic Resonance ◽  
Spin Lattice ◽  
The Stability ◽  
Calcium Doping ◽  
Electron Paramagnetic

Polycrystalline solid solution of phosphate and vanadate lead calcium apatites Pb 10 -x Ca x( VO 4)1( PO 4)5( OH )2 apatites [x = 0.0, 2.0, 4.0, 6.0, 8.0, and 10.0] was reduced with hydrogen gas at the temperature of 300 and 400°C for 1 h. All these compounds were investigated by XRD and ESR spectroscopy. Only one reduced oxidation state V +4 was detected. Two types of species like isolated vanadium (+4) and clusters of V 4+ had been observed. The stability of the apatites increases and the particle size of the crystal decreases with calcium doping concentrations. As the concentrations of Ca increase the intensity of ESR lines deviates due to the spin–lattice relaxation interactions. The deviation in the intensity of ESR spectra can be attributed as the coexistence of paramagnetic and antiferromagnetic phases in the apatites.

THE SPIN HAMILTONIAN PARAMETERS CALCULATION OF 14N AND 15N IN NATURAL TYPE I DIAMOND

2008 ◽  
Vol 22 (25n26) ◽  
pp. 4740-4748 ◽  
Author(s):  
CHITTRA KEDKAEW ◽  
PICHET LIMSUWAN ◽  
KANPHOT THONGCHAM ◽  
SIWAPORN MEEJOO
Keyword(s):  
Natural Diamond ◽  
Microwave Frequency ◽  
Esr Spectra ◽  
Type I ◽  
Spin Hamiltonian ◽  
X Band ◽  
Natural Type ◽  
Hamiltonian Parameters ◽  
Parameters Calculation ◽  
Resonance Magnetic Field

The main purpose of this work is to present the ESR spectra and calculate the spin Hamiltonian parameters of 14 N and 15 N impurities in natural diamond. The ESR spectra of diamond crystal were measured on ESR spectrometer operating at X-band microwave frequency. The results of ESR spectra show that the diamond has a P1 center. This center gives rise to three strong resonance absorption peaks at θ = 90°, φ = 0° due to hyperfine interaction between electron spin and nuclear spin of 14 N . The ESR spectra of 15 N impurity consist of two satellites at the same rotation angle (φ). The effects of isolated substitution nitrogen on carbon atom produced a symmetric distortion from Td to C3V symmetry. According to this symmetry, the resonance magnetic field positions of ESR spectra for the rotation angles of 0°, 90° and 180° are almost overlap. The g-factor values and spin Hamiltonian parameters of 14 N and 15 N are: g = 2.0019, A⊥ = 29.73, A‖ = 40.24 and g = 2.0019, A⊥ = −39.90, A‖ = −57.05, respectively.

scholarly journals Oxovanadium(IV) complexes of bromo-and methoxy substituted N1,N4-diarylidene-S-methylthiosemicarbazones

2006 ◽  
Vol 4 (1) ◽  
pp. 149-159 ◽  
Author(s):  
Tülay. Demirci ◽  
Yüksel Köseoğlu ◽  
Sadik Güner ◽  
Bahri Ülküseven
Keyword(s):  
Epr Spectroscopy ◽  
Magnetic Measurements ◽  
Energy Levels ◽  
Orbital Energy ◽  
Spin Hamiltonian ◽  
X Band ◽  
Solid Compounds ◽  
Hamiltonian Parameters ◽  
Vanadium Ions ◽  
Template Reaction

AbstractFour new oxovanadium(IV) compounds were prepared by template reaction of salicyl-, 5-bromosalicyl-and 3-methoxysalicyl-aldehyde S-methylthiosemicarbazones with 2-hydroxy-, 5-bromo-2-hydroxy-and 3-methoxy-2-hydroxy-benzaldehyde in various combinations. The compounds were isolated as stable solid compounds with general formula [VO(L)] and characterized by elemental analysis, conductivity and magnetic measurements, electronic, IR and EPR spectroscopy. The X-band EPR signals recorded from powder forms of all samples have a single asymmetric line shape and theoretical fit studies proved the presence of axial symmetry around the paramagnetic vanadium ions. The anisotropic Lande splitting factors take values of g‖ < g⊥ < ge = 2.0023. Orbital energy levels for magnetic electrons were determined from theoretically well fitted Spin Hamiltonian parameters. The EPR spectra recorded from solution forms almost have isotropic character.

scholarly journals Electron Spin Resonance Of Vo2+ In Likso4 Single Crystals

2004 ◽  
Vol 59 (7-8) ◽  
pp. 488-490
Author(s):  
Manu Jain
Keyword(s):  
Electron Spin Resonance ◽  
Single Crystals ◽  
Electron Spin ◽  
Esr Spectra ◽  
Spin Hamiltonian ◽  
X Band ◽  
Spin Resonance ◽  
Hamiltonian Parameters

Electron spin resonance of VO2+ doped in LiKSO4 single crystals has been studied at 295 K, using an X-band spectrometer. Three sites have been observed. VO2+ enters the lattice at Li and K substitutional sites. The ESR spectra have been analysed and spin-Hamiltonian parameters evaluated. PACS: 76.30 F

Theoretical Study of the Spin Hamiltonian Parameters of Vanadium Ions V2+ in CsMgX3 (X = Cl, Br, I)

2005 ◽  
Vol 60 (3) ◽  
pp. 145-148 ◽  
Author(s):  
Xiu-Ying Gao ◽  
Shao-Yi Wu ◽  
Wang-He Wei ◽  
Wei-Zi Yan
Keyword(s):  
Hyperfine Structure ◽  
Theoretical Study ◽  
Spin Hamiltonian ◽  
Octahedral Symmetry ◽  
Cluster Approach ◽  
G Factor ◽  
Structure Constants ◽  
Hamiltonian Parameters ◽  
Theoretical Results ◽  
Vanadium Ions

The spin Hamiltonian g factors and the hyperfine structure constants for V2+ in CsMgX3 (X = Cl, Br, I) are theoretically studied by using the perturbation formulas of these parameters for a 3d3 ion in octahedral symmetry, based on the cluster approach. In such formulas, the contributions from the s-orbitals of the ligands were usually neglected. Here they are taken into account. The theoretical results (particularly the g factor for CsMgI3) show a significant improvement compared with those in absence of the ligand s-orbital contributions in the previous studies.

Electrochemical behaviour and ESR spectra of nitro substituted mono- and dibenzoylmethylenebenzthiazolines and selenazolines

1979 ◽  
Vol 44 (5) ◽  
pp. 1540-1551 ◽  
Author(s):  
Jaro Komenda ◽  
Jiří Huzlík
Keyword(s):  
Electron Transfer ◽  
Esr Spectroscopy ◽  
Electrochemical Behaviour ◽  
Spectroscopic Studies ◽  
Esr Spectra ◽  
Slow Electron

Compounds of the type of 2-(4'-nitrobenzoyl)methylene-3-ethylbenzothiazoline (I) and 2-bis-(p-nitrobenzoyl)methylene-3-ethylbenzothiazoline (II) were studied polarographically and by ESR spectroscopy to obtain informations about their electrochemical and follow-up reactions and their conformation. Whereas with compounds of the type I the conjugation in their molecules is preserved, with type II the coplanarity of the molecules is disturbed, which is manifested in the values of the splitting constants of the ESR spectra and a slow electron transfer between both nitrophenyl substituents. These conclusions are supported by NMR spectroscopic studies.

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