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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An analysis of the experimental EPR spectrum of γ-irradiated barium dithionate is made. Based on the data obtained, a model of this spectrum is constructed. It is shown that the spectrum results from superposition of four individual signals, for which the following values of the g-factor components have been determined: for I g M = 2.0097, g N = 2.0044; for II g M = 2.0069, g N = 2.0023; for III g M = 2.0042, g N = 2.0032; for IV g M = 2.0002 and g N = 2.0032.Introduction. The spin-resonance method of determining an absorbed dose D of ionizing radiation with the aid of barium dithionate (BaS 2 O 6 ⋅2H 2 O) is based on measurement of the concentration C of stable radiation-induced ion radicals, given the known coefficient of the linear function C = f(D). In this case, to determine the concentration with a minimum error, it is necessary to make use of a calculation model of the EPR spectrum of irradiated barium dithionate that would be appropriate for the experimental spectrum. Then it becomes possible, firstly, to most accurately determine the area of the corresponding EPR signal and, secondly, to reduce the threshold of the radiative sensitivity of a dosimeter. First of all, the latter is of current interest for medical radiology, where small doses of ionizing radiation are used and, therefore, there are small-intensity signals often comparable with the noise level. Based on the results of an analysis of the experimental EPR spectrum of irradiated barium dithionate, an attempt is made in the present work to construct a model spectrum that would approximate the experimental one as closely as possible.Experimental Procedure. The technique of producing barium dithionate used in the experiment and the methods of testing the degree of its purity are described in [1,2].Fine-crystalline barium dithionate was exposed to γ-radiation in an air medium at atmospheric pressure and a temperature of 20 o C on a PXM-γ20 ( 60 Co) setup. Doses of 1, 5, 10, 25, 30, 40, 50, and 60 kGy were used. The irradiated samples were heated in air under isothermal conditions at temperatures of 75 and 80 o C. The process was monitored by the EPR method. The spectra were registered on a compact computerized spectrometer (λ = 3 cm) at 20 o C. When the values of g-factors were measured, MgO containing Mn 2+ ions was used as an external standard. The error of measurements was ±0.0004.Results and Discussion. In [3] it is established that the EPR signal of γ-irradiated barium dithionate is complex and consists of four components I-IV that were revealed by us in the course of heating the investigated substance at 80 o C under isothermal conditions (Fig. 1a, curves 1 and 5). The spectrum is also separated into components when the power P of the microwave oscillator of the spectrometer is increased (the interval considered is 10-79 mW, Fig. 1b) The situation of separation is simplified because the dependence of the relative intensity I of central component III on P, unlike the dependences observed for the remaining three components, exhibits an extreme...