Electron spin resonance of sulfite radicals in irradiated calcite and aragonite

Kai, Ayako; Miki, Toshikatsu

doi:10.1016/1359-0197(92)90211-w

Cited by 22 publications

(20 citation statements)

References 28 publications

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“…In this case, the width of the line remains unchanged, which presupposes an isolated state of the corresponding kind of ion-radicals SO 3 − (iso) in the structure of sulfite. However, the isotropicity of the signal C points to the possibility of free rotation of these ion-radicals, which is similar to that suggested for the ion-radicals SO 2 − (iso) in calcite [10] and for SO 3 − (iso) in kainite [13]. On the contrary, in the ion-radicals SO 3 − (axial) that are responsible for the signal B the free rotation must be retarded.…”

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confidence: 64%

“…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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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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Stabilization of Ion-Radicals in the Structure of Calcium Sulfite

Bogushevich

Ugolev

2005

J Appl Spectrosc

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“…4a. The signal of axial SO3 (g1 = 2.0038 and g ii = 2.0024, [7]), which has been used for dating, is detected along with intense natural Mn z + signals. The ESR signal of orthorhombic CO z radicals (g5X = 2.0030, gz = 2.0014 and g 1.9974, [10]) commonly used for the dating of shells is not clearly detected in this sample, perhaps because it is overlapped by the natural Mn2+ signals.…”

Section: Esr Spectrummentioning

confidence: 99%

Calibration method for ESR signal intensity of calcitic shells

et al. 2000

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A practical method of calibrating intensities of ESR signals with a single crystal of copper pentahydrate (CuSO 4 • 5H20) has been developed for calcitic shells containing a large amount of manganese (Mn 2 '). A sample holder is designed to insert the crystal from the bottom of the cavity for use as a standard sample. The signal of Cu e in the standard does not interfere with the Mn2 ' signals. The Cue signal and dating signal of the shell are recorded simultaneously; the ratio of their intensities is the basis for calibration. It is shown that this calibration method reduces the errors attributed to both coupling and unloaded Q factors of the cavity resonator to within 2%.

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“…The magnetic field was corrected by a Gaussian meter (NMR Field Meter ES-FC5, JEOL Ltd., Tokyo, Japan) at the end of every measurement. The accuracy of magnetic fields was further confirmed by a single crystal of DPPH (1,1-Diphenyl-2-picrylhydrazyl; g = 2.00366 ± 0.00004) [35][36][37], which was used as a standard of g-values. The temperature (77 K), sweep time (30 s), modulation (100 kHz), microwave power (0.998 mW), and time constant (0.01 s) were identical for each salt and common to the measurements under dark and irradiated conditions.…”

Section: Electron Spin Resonance (Esr)mentioning

confidence: 99%