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The electron paramagnetic resonance (EPR) parameters (g factors g_{i} and the hyperfine structure constants A_{i}, i = x, y, z) are interpreted by using the perturbation formulae for a 3d^{9} ion in rhombically (D_{2h}) elongated octahedra. In the calculated formulae, the crystal field parameters are set up from the superposition model, and the contribution to the EPR parameters from the admixture of d-orbitals in the ground state wave function of the Cu^{2+} ion was taken into account. Based on the calculation, local structural parameters of the impurity Cu^{2+} center in Cd_{2}(NH_{4})_{2}(SO_{4})_{3} (CAS) crystal were obtained (i.e., R_{x} ≈ 2.05 Å, R_{y} ≈ 1.91Å, R_{z} ≈ 2.32 Å). The theoretical EPR parameters based on the above Cu^{2+}-O^{2-} bond lengths in CAS crystal show a good agreement with the observed values. The results are discussed.

On the basis of the perturbation formulas for a d^1 configuration ion in a tetragonal crystal field, the three optical absorption bands and electron paramagnetic resonance (EPR) parameters (g factors g_i and hyperfine structure constants A_i for i = || and ⊥, respectively) of VO^{2+} in Na_3C_6H_5O_7·2H_2O (TSCD) single crystals were studied using the perturbation theory method. By simulating the calculated optical and EPR spectra to the observed values, local structure parameters and negative signs of the hyperfine structure constants A_i of the octahedral (VO_6)^{8-} cluster in TSCD single crystal can be obtained.

Electron spin resonance spectral parameters (g factors g‖ g⊥ and hyperfine structure constants A‖, A⊥) of a tetragonal V4+ centers in MB4O7 (M = Zn, Cd) are theoretically investigated by using the perturbation formulae for a 3d1 ion in tetragonally compressed octahedra. In these formulae, the contributions to the g factors from the tetragonal distortion, characterized by the tetragonal field parameters Ds and Dt are taken into account by considering the local structures of the ligand octahedron around the V4+ due to the Jahn-Teller effect. Based on the calculations, the ligand octahedra around V4+ are suggested to suffer about 5.7% and 4.3% relative compression along C4 axis for MB4O7 glasses with M = Zn and Cd, respectively, and negative signs of the hyperfine structure constants Ag‖ and Ag⊥ for V4+ centers in MB4O7 glasses were suggested in the discussion. [ABSTRACT FROM AUTHOR]