The nature of the paramagnetic centres at g = 2.0057 and g = 2.0031 in marine carbonates

Barabas, Michael

doi:10.1016/1359-0189(92)90031-p

Cited by 68 publications

(18 citation statements)

References 38 publications

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“…It contains a rather intense narrow isotropic signal (denoted by A) with g(iso) = 2.0055 and a line width ∆H = 0.13 mT. A similar signal (with g(iso) = 2.0053 [6]; 2.0054 [7]; 2.0057 [2,8], and 2.0060 [9,10]) was revealed in the EPR spectra of irradiated natural and synthetic carbonates. In [2,7,10], the reason for the appearance of the paramagnetic particles responsible for this signal was related to the presence of impurity sulfate-ions in specimens and assigned them to radiatively induced ion-radicals SO 2 − (iso).…”

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confidence: 88%

“…1, spectra 2 and 3). The resulting mechanically induced paramagnetic particles with such spectral charac-teristics entirely correspond to radiatively induced ion-radicals SO 3 − (axial) with the g factors g M = 2.0038, g N = 2.0024 [3,10] or g M = 2.0036, g N = 2.0021 [2] registered in natural and synthetic calcites, and on this basis they were assigned by us to this type of particle. It should be noted that in the spectra of irradiated natural carbonates these two EPR signals (both isotropic and anisotropic) are considered to be acceptable for carrying out measurements of absorbed doses [6,9].…”

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confidence: 99%

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Stabilization of Ion-Radicals in the Structure of Calcium Sulfite

Bogushevich

Ugolev

2005

J Appl Spectrosc

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Using the EPR-and IR-spectroscopy methods, we studied the conditions of formation of stable ion-radicals in the structure of calcium sulfite and determined the limits of their stability. We detected and identified the ionradicals SO 2 − with g(iso) = 2.0055 in the initial substances, two types of thermally induced SO 2 − (with g 1 = 2.0093, g 2 = 2.0045, and g 3 = 2.0020, and g 1 = 2.0104, g 2 = 2.0049, and g 3 = 2.0018) when the substance was heated, and three types of mechanically induced SO 3 − (with g M = 2.0036 and g N = 2.0022, with g(iso) = 2.0033 and ∆H = 0.1 mT and with g(iso) = 2.0031 and ∆H = 0.33 mT) when the substance was ground up.Keywords: EPR and IR spectroscopy, EPR dosimetry, sulfite and sulfate anions, SO 2 − and SO 3 − ion-radicals.Introduction. One possible method of reconstruction of absorbed doses of ionizing radiations applied in spinresonance dosimetry and in the region of EPR dating of geological and archeological materials is the cumulative-dose method [1]. It is based on determination of the concentration of accumulated radiatively induced paramagnetic particles and involves an initial mechanical or thermal processing of the object under study and subsequent additional irradiation of this object. In the course of preliminary preparation, mechanically and thermally induced paramagnetic particles can form in the substance that have g factors close to the values of the g factors (or coinciding with them) for radiatively induced paramagnetic particles. As a result, additional, often neglected, errors are brought into the unknown value of the reconstructed dose and make its determination difficult. In view of this, there is a pressing need to investigate the nature of nonradiative paramagnetic particles, the mechanisms of their formation, and the conditions of stabilization in a substance.Along with other materials, carbonates of natural origin are used to reconstruct absorbed doses. The characteristic feature of these carbonates is the presence of sulfite-anions [2, 3]. Moreover, it is known that such a compound as barium sulfite in the absence of irradiation is capable of stabilizing ion-radicals in its structure [4,5]. Starting from this, it is the aim of the present work to elucidate the nature, the conditions of formation, and the stability of paramagnetic particles in the structure of nonirradiated calcium sulfite (CaSO 3 ), which is necessary for further evaluation of their contribution to the unknown value of the absorbed dose in natural carbonates.Experimental Technique. Calcium sulfite was synthesized at 20 o C by adding a solution of sodium sulfite to a solution of calcium chloride with subsequent filtering of the sediment and drying of it in air without heating. The purity of the salt obtained was controlled by x-ray phase analysis and IR spectroscopy. We used a DRON-3 x-ray diffractometer and a Prote ′ ge ′ 760 IR Fourier-spectrophotometer (Nicolet, USA). Specimens were tableted together with KBr.The calcium sulfite obtained was divided into two parts, one of which was ground u...

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confidence: 99%

Stabilization of Ion-Radicals in the Structure of Calcium Sulfite

Bogushevich

Ugolev

2005

J Appl Spectrosc

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“…The g-factor value of 2.0057 in carbonates has been interpreted by many authors (see e.g. Barabas, 1992;Ikeya, 1993 and2004) as the SO 2 -centre. In this case, however, it is presumably a part of a triplet, not a single line, so its nature should be studied further before assigning it to this species.…”

Section: Resultsmentioning

confidence: 99%

“…Sample 61H, which is the fraction 63-80 µm of a mortar, gives the EPR spectrum least affected by the presence of the triplet signal, presumably because the component that the signal was originating from was almost completely eliminated during sieving. Spectra of 61H exhibits the signals at g = 2.0034, 2.0013 and 1.9971 attributed to CO 2 -species; the peaks at 2.0034 and 2.0013 may be also interpreted as the axial CO 3 3-paramagnetic centre (Barabas, 1992;Barabas et al, 1992;Ikeya, 1993 and2004;Callens et al, 1998;Wencka and Krzyminiewski, 2004). Other peaks can be observed at g = 2.0424, 2.0209, 2.0156, 2.0102, 2.0082, 2.0057 and 2.0048.…”

Section: Resultsmentioning

confidence: 99%

Investigation of lime mortars and plasters from archaeological excavations in Hippos (Israel) using Electron Paramagnetic Resonance

et al. 2014

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This study presents the preliminary results of investigation of the lime mortars and plasters from archaeological excavations in Hippos (Israel), using Electron Paramagnetic Resonance (EPR) spectroscopy. The research was conducted in order to characterize the building material and its reaction to ionizing radiation. The ancient settlement Hippos, situated on the east shore of the Sea of Galilee, functioned from the 3 rd cent. BC until it was destroyed by the earthquake in 749 AD. Lime mortars and plasters show carbonate and locally gypsum character of binder and different kind of aggregate. Samples were γ-irradiated and measured using X-band EPR spectrometer. Computer Resolution Enhancement Method was applied to the complex spectra. Some of the γ-induced EPR signals were attributed to CO 2 -and CO 3 3-paramagnetic centres. Exponential growth of the dose response curve above 1 kGy and saturation for doses above 20 kGy was observed. For doses lower than 1 kGy the dose response curve has a linear character. The presence of γ-sensitive carbonate paramagnetic centres could indicate that, after further studies, well-chosen samples of mortars and plasters might be suitable for EPR dating, assuming the centres have been sufficiently bleached during the manufacturing process.

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“…The main ESR features of signais observed in Quaternary carbonates are summarized in Barabas (1992).…”

Section: Esr Spectra Of Carbonatesmentioning

confidence: 99%

Thermal behaviour of ESR signals observed in various natural carbonates

Bahain

Yokoyama

Masaoudi

et al. 1994

Quaternary Science Reviews

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The thermal behaviour of thé five main ESR lines observed in Quaternary carbonates (g=2.0057, g=2.0031, g=2.0018, g=2.0006 and g= 1.9972) was studied through isochron annealing experiments. As thé général rule, ESR lines are more stable in calcitic samples than in aragonîtic ones and in speleothems than in marine carbonates. In ail thé studied carbonates, thé most stable signais are g=2.0057 and g=2.0031, then g=2.0006.

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The nature of the paramagnetic centres at g = 2.0057 and g = 2.0031 in marine carbonates

Cited by 68 publications

References 38 publications

Stabilization of Ion-Radicals in the Structure of Calcium Sulfite

Stabilization of Ion-Radicals in the Structure of Calcium Sulfite

Investigation of lime mortars and plasters from archaeological excavations in Hippos (Israel) using Electron Paramagnetic Resonance

Thermal behaviour of ESR signals observed in various natural carbonates

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