EPR spectra of a new radiation-induced paramagnetic centre in kaolins

Clay Minerals ◽  
2016 ◽  
Vol 51 (5) ◽  
pp. 707-714 ◽  
Author(s):  
Bernard A. Goodman ◽  
Niramon Worasith ◽  
Wen Deng
Keyword(s):  
Radiation Dose ◽  
Spin Hamiltonian ◽  
Paramagnetic Centre ◽  
Epr Spectrum ◽  
Γ Radiation ◽  
Rhombic Symmetry ◽  
Radiation Induced ◽  
Epr Signal ◽  
A Minor ◽  
Hamiltonian Parameters

AbstractThe EPR spectrum of a previously unreported paramagnetic centre formed in kaolin minerals by exposure to γ radiation is described. This centre, which is referred to here as the ‘C-centre’, was seen initially during an investigation of the radiation dose response of the EPR signal in the natural Lampang kaolin from northern Thailand, and its EPR properties are now presented for a purified sample from this material. They suggest a paramagnetic centre with rhombic symmetry based on O− associated with a single 27Al atom. Computer simulations suggest spin Hamiltonian parameters of g1 = 1.976, g3 = 2.0417 and A(27Al) = 2.10 mT, with g2 ≈ 2.01. This C-centre was also seen as a minor radiationinduced component in both crude and purified Ranong kaolin samples, along with a stronger signal from the B-centre radical. It seems to be associated with the kaolinite component, but was lost on annealing to 300°C after which only the signal from the A-centre was visible.

EPR Studies of Mn2+-Doped Diammonium Hexaaqua Magnesium(II) Sulfate

2006 ◽  
Vol 61 (12) ◽  
pp. 683-687 ◽  
Author(s):  
Ram Kripal ◽  
Ashutosh Kumar Shukla
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Fine Structure ◽  
Single Crystals ◽  
Room Temperature ◽  
Spin Hamiltonian ◽  
Epr Spectrum ◽  
Paramagnetic Resonance ◽  
X Band ◽  
Hamiltonian Parameters ◽  
Electron Paramagnetic

Electron paramagnetic resonance (EPR) studies of Mn2+ impurity in single crystals of diammonium hexaaqua magnesium(II) sulfate have been carried out at 9.3 GHz (X-band) at room temperature. The EPR spectra exhibit a group of five fine structure transitions. The spin-Hamiltonian parameters were determined. Mn2+ enters the lattice interstitially. The EPR spectrum of a powder sample supports the data obtained by single crystal studies. - PACS number: 76.30

scholarly journals Identification of irradiated dried fruits using EPR spectroscopy

Nukleonika ◽  
2015 ◽  
Vol 60 (3) ◽  
pp. 627-631 ◽  
Author(s):  
Grzegorz P. Guzik ◽  
Wacław Stachowicz ◽  
Jacek Michalik
Keyword(s):  
Gamma Rays ◽  
Radiation Treatment ◽  
Prolonged Storage ◽  
Epr Spectrum ◽  
Radiation Chemical ◽  
Dried Fruits ◽  
Radiation Induced ◽  
Epr Signal ◽  
Chemical Products ◽  
One Year

Abstract The dominating carbohydrates in fruits are monosaccharides like fructose, glucose, sorbose and mannose. In dehydrated fruits, concentration of monosaccharides is higher than in fresh fruits resulting in the formation of sugar crystallites. In most of dried fruits, crystalline fructose, and glucose dominate and appear in proportion near to 1:1. Irradiation of dried fruits stimulates radiation chemical processes resulting in the formation of new chemical products and free radicals giving rise to multicomponent EPR signal which can be detected for a long period of time. For that reason, it is used as a marker for the detection of radiation treatment of dried fruits. It has been found that EPR spectra recorded in dried banana, pineapple, papaya, and fig samples resemble the EPR spectrum obtained by computer addition of fructose and glucose spectra taken in proportion 1:1. The decay of radiation induced EPR signals proceeds in dried fruits fast during the first month of observation and becomes much slower and almost negligible after prolonged storage. However, it remains intense enough for EPR detection even one year after processing. The radiation induced EPR signal is easily detected in dried fruits exposed to 0.5 kGy of gamma rays. Thus, the EPR method of the detection of irradiated fruits can be used for the control of dried fruits undergoing quarantine treatment with 200-300 Gy of ionizing radiation.

EPR Spectra of Some Cu2+-Doped Metal Carbonates and Disorder Phase Transition in K3H(CO3)2

2009 ◽  
Vol 64 (1-2) ◽  
pp. 123-126 ◽  
Author(s):  
Dilek Demir ◽  
Fevzi Köksal ◽  
Canan Kazak ◽  
Rahmi Köseoğlu
Keyword(s):  
Phase Transition ◽  
Low Temperatures ◽  
The Other ◽  
Spin Hamiltonian ◽  
Epr Spectrum ◽  
Paramagnetic Resonance ◽  
Disorder Phase Transition ◽  
Metal Carbonates ◽  
Hamiltonian Parameters ◽  
Electron Paramagnetic

Cu2+-doped K3H(CO3)2, Rb2CO3, and Rb2KH(CO3)2 single crystals were investigated by electron paramagnetic resonance (EPR) spectroscopy. The EPR spectrum of K3H(CO3)2 indicates two different sites for Cu2+ at room and at low temperatures. But the signals for the two sites overlap at 318 K which is attributed to a disorder phase transition. Each of the other compounds exhibits one site. The Cu2+ ion seems to substitute the K+ and Rb+ ions and the charge compensations are fulfilled by the proton vacancies in K3H(CO3)2, and another K+ and Rb+ in the other compounds. The spin Hamiltonian parameters g and A for each compound are determined and discussed.

A Theoretical Study on the Spin-Hamiltonian Parameters for Samarium(III) Ion in Potassium Yttrium Tungstate Crystal

2011 ◽  
Vol 66 (3-4) ◽  
pp. 139-142 ◽  
Author(s):  
Wei-Qing Yang ◽  
Wen-Chen Zheng ◽  
Ping Su ◽  
Hong-Gang Liu
Keyword(s):  
Crystal Field ◽  
Theoretical Study ◽  
Spin Hamiltonian ◽  
Energy Matrix ◽  
Interaction Terms ◽  
Rhombic Symmetry ◽  
Diagonalization Method ◽  
Structure Constants ◽  
Experimental Values ◽  
Hamiltonian Parameters

The nine spin-Hamiltonian (SH) parameters (g-factors gi and hyperfine structure constants 147Ai and 149Ai for 147Sm3+ and 149Sm3+ isotopes, where i = x, y, z) for the Samarium(III) ion in monoclinic potassium yttrium tungstate [KY(WO4)2] crystal are calculated within the rhombic symmetry approximation from a diagonalization of energy matrix method. Differing from the conventional diagonalization method used in the calculation of crystal-field levels, in the present method, we attach the Zeeman (or magnetic) and hyperfine interaction terms to the conventional Hamiltonian and construct the 66×66 energy matrix for 4f5 ions in rhombic crystal field and under an external magnetic field by considering all the ground-term multiplets 4HJ. The calculated results are in reasonable agreement with the experimental values

ELECTRON PARAMAGNETIC RESONANCE OF MANGANESE IN CESIUM AND AMMONIUM CHLORIDES

1967 ◽  
Vol 45 (10) ◽  
pp. 3381-3386 ◽  
Author(s):  
A. Forman ◽  
J. A. Van Wyk
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Fine Structure ◽  
Line Width ◽  
Structure Parameter ◽  
Manganese Ions ◽  
Spin Hamiltonian ◽  
Epr Spectrum ◽  
Paramagnetic Resonance ◽  
Hamiltonian Parameters ◽  
Electron Paramagnetic

The spin-Hamiltonian parameters describing the EPR spectrum of Mn2+ in CsCl crystals grown from solutilon have been determined. The line-width data are in agreement with the manganese ions being incorporated interstitially rather than substitutionally for Cs+ ions. From the work on Mn2+ in NH4Cl we infer that the fine structure parameter, D2, is negative.

scholarly journals Статический и динамический вклады в расщепление основного состояния Eu-=SUP=-2+-=/SUP=- в SrMoO-=SUB=-4-=/SUB=-

2019 ◽  
Vol 61 (5) ◽  
pp. 905
Author(s):  
А.Д. Горлов
Keyword(s):  
Thermal Expansion ◽  
Single Crystal ◽  
Impurity Center ◽  
Spin Hamiltonian ◽  
Lattice Thermal Expansion ◽  
Epr Spectrum ◽  
Small Temperature ◽  
Temperature Changes ◽  
Hamiltonian Parameters ◽  
Static Lattice

AbstractThe EPR spectrum of an Eu^2+ impurity center in a SrMoO_4 single crystal in the temperature range T = 1.8, 111–300 K has been studied, and the temperature changes in the spin Hamiltonian parameters describing the EPR spectrum of odd europium isotopes have been determined. It is shown that small temperature changes in the diagonal parameters of the spin Hamiltonian (for odd Eu^2+ isotopes) $$b_{2}^{0}$$ ( T ) = b _2( F ) + b _2( L ) and $$P_{2}^{0}$$ ( T ) = P _2( F ) + P _2( L ) are explained by the compensation of spin–phonon contributions b _2( F ) and P _2( F ) by the contributions of the lattice thermal expansion b _2( L ) and P _2( L ). The quantities b _2( L ) and P _2( L ) that are dependent on the static lattice parameters at a given temperature, are estimated in terms of the superposition Newman model. Then, the spin–phonon b _2( F ) and P _2( F ) contributions determined by the lattice ion vibrations are separated. An analysis shows that $$b_{2}^{0}$$ ( F ) and $$P_{2}^{0}$$ ( F ) > 0, b _2( L ) and P _2( L ) < 0, and the temperature behavior of the spin–phonon contribution is well described by G. Pfister’s model of local vibrations.

scholarly journals Identification of the Negative Carbon Vacancy at Quasi-Cubic Site in 4H-SiC by EPR and Theoretical Calculations

2014 ◽  
Vol 778-780 ◽  
pp. 285-288
Author(s):  
Xuan Thang Trinh ◽  
Krisztián Szász ◽  
Tamas Hornos ◽  
Koutarou Kawahara ◽  
Jun Suda ◽  
...  
Keyword(s):  
Room Temperature ◽  
Defect Formation ◽  
Theoretical Calculations ◽  
Low Energy ◽  
Spin Hamiltonian ◽  
Epr Spectrum ◽  
Paramagnetic Resonance ◽  
Carbon Vacancy ◽  
Hamiltonian Parameters ◽  
Electron Paramagnetic

In freestandingn-type 4H-SiC epilayers irradiated with low-energy (250 keV) electrons at room temperature, the electron paramagnetic resonance (EPR) spectrum of the negative carbon vacancy at the hexagonal site, VC- (h), and a new signal were observed. From the similarity in defect formation and the spin-Hamiltonian parameters of the two defects, the new center is suggested to be the negative C vacancy at the quasi-cubic site, VC- (k). The identification is further supported by hyperfine calculations.

scholarly journals Парамагнитные центры хрома в кристаллах Y-=SUB=-2-=/SUB=-SiO-=SUB=-5-=/SUB=- и Sc-=SUB=-2-=/SUB=-SiO-=SUB=-5-=/SUB=-

2018 ◽  
Vol 60 (10) ◽  
pp. 1995
Author(s):  
В.А. Важенин ◽  
А.П. Потапов ◽  
Г.С. Шакуров ◽  
А.В. Фокин ◽  
М.Ю. Артёмов ◽  
...  
Keyword(s):  
Single Crystals ◽  
Spin Hamiltonian ◽  
Epr Spectrum ◽  
Chromium Ions ◽  
Hamiltonian Parameters

AbstractThe EPR spectrum of yttrium and scandium silicate single crystals doped with chromium has been studied at various frequencies. Y_2SiO_5 has one triclinic Cr^3+ center, while the Sc_2SiO_5 crystals demonstrate two nonequivalent centers. The spin Hamiltonian parameters of these centers have been determined. These centers are found to be tricharged chromium ions localized in the yttrium and scandium positions.

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