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PACS 61.72. Ji, 76.30.Mi Connected with alkaline metal impurities axial V centres were studied by EPR in SrS and CaS polycrystals. A paramagnetic S À ion arises near an alkaline metal ion substituting for a cation of the host lattice after a hole produced by X-raying at 77 K is captured. The centres are observable at low temperatures of 10-25 K. The superhyperfine structure from a 23 Na nucleus and a 7 Li nucleus was observed. Parameters of V centres (g-tensor and A-tensor values, thermal decay) are determined.

Two different paramagnetic centres of a similar nature are studied by EPR in CaS polycrystals plastically deformed at 300 K after annealing at 575 to 825 K and subsequent X-raying of the samples at room temperature. These centres arise most likely from cation±anion vacancy pairs after an electron is captured at the anion vacancy. The electron is released in different temperature ranges if the cation and anion vacancies are either the nearest (nn) neighbours (365 to 515 K), or the next nearest (nnn) neighbours (475 to 625 K) in the CaS lattice. Both vacancy pairs are formed when migrating cation vacancies are captured by anion vacancies at annealing in the range of temperatures 575 to 675 K. (nnn) vacancy pairs are transformed into (nn) pairs at 675 to 725 K, while both complexes decrease in number and disappear at 725 to 825 K.

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