[en] Carbonated fluorapatites were prepared by precipitation, using calcium acetate. After irradiation and annealing at 150⁰C the X-band ESR spectrum of the CH₃ radical was recorded. The spin Hamiltonian parameters were determined at RT, 110⁰K, and 16⁰K. From the thermal behavior of the spectrum it is deduced that different recombination processes of the defect are involved. This radical originates from the degradation of acetate ions trapped at anion sites of the tunnels

No abstract available

[en] The hydration of single-crystal La₂O₃ samples was studied following the evolution versus time of ESR spectra of Gd³⁺ and Mn²⁺ ions which enter the lattice substitutionally at lanthanum sites. The results, which confirm those obtained previously on the macroscopic scale, permit a better understanding of the hydration process on the atomic scale

[en] In irradiated synthetic single crystal calcite two defects which are CO₃^3- ions associated with lithium impurities are observed. Both defects are axially symmetric along the calcite c axis. One defect is associated with one Li⁺ ion, the other with two Li⁺ ions. The values of the various constants of the spin hamiltonians describing the spectra of both defects are given. The spin densities in the 2s lithium orbitals are 2.96% for the one lithium centre and 11.89% and 0.1 per mille in the case of the two lithiums centre. Some hypothesis concerning the location of the various Li⁺ ions are presented

[en] The electron spin resonance of Mn²⁺ ions was used to study the zirconia-calcia system from 9 to 60 mole% CaO. With the exception of single crystals of calcia-stabilized zirconia (CSZ) with 15 and 20 mole% CaO, the experiments were carried out on polycrystalline samples. From the different values measured for the hyperfine coupling constant A with increasing amount of calcia, it was deduced that Mn²⁺ substitutes for Ca²⁺ in the three following host lattices: cubic CSZ, CaZrO₃, and CaO

[en] Position and intensity of (ΔM = 1, Δm = 1) forbidden hyperfine lines arising in the central transition of the Mn²⁺:La₂O₃ ESR spectrum are analyzed by means of the existing theories. This made it possible to determine the quadrupole coupling constant and the nuclear Zeeman term. (author)

[en] EPR spectrum of Gd³⁺ ion in ThO₂ monocrystal was investigated in the temperature range 119-568 K. Spectrum had cubic symmetry with the slight admixture of lines of axial symmetry. The strong dependence of b₄⁰ on temperature was observed. It was interpreted as a result of the change of inter-ionic distance. (Z.M.)

[en] EPR spectra of the (CO₃Li)^2--Li⁺ defect in x-irradiated single-crystal calcite were observed at RT immediately after irradiation. From the resolved hyperfine structure due to the coupling of the unpaired electron spin and the nuclear spin I = 1/2 of ¹³C the O-C-O bond angle could be evaluated. Using the LCAO-MO method the wave function of the single electron was established. This permitted a model for the (CO₃Li)^2--Li⁺ center to be proposed

[en] X-band room temperature EPR spectra have been recorded for Mn²⁺ ion doping unannealed (La₂O₃)sub(0.95)(CeO₂)sub (0.05) host crystal. The data are analysed using a rigorous least-squares fitting procedure in which a large number of lines characterized by ΔM = +- 1, Δm = 0 transition, obtained for several orientations of the static magnetic field, are simultaneously fitted. Combined with the knowledge of the absolute sign of the hyperfine interaction parameter A, the hyperfine Hamiltonian parameters A,B,Q as reported in this paper, are given with their correct signs. The information on the linewidths is used to deduce the deviation of the crystal-field axes of different Mn²⁺ ions from the c axis; on the basis of the model proposed here these deviations are found to be between 0 and 10⁰. (author)

No abstract available