Electron spin resonance spectral parameters (g factors g , g ⊥ and hyperne structure constants A , A ⊥ ) of a tetragonal V 4+ centers in MB4O7 (M = Zn, Cd) are theoretically investigated by using the perturbation formulae for a 3d 1 ion in tetragonally compressed octahedra. In these formulae, the contributions to the g factors from the tetragonal distortion, characterized by the tetragonal eld parameters Ds and Dt are taken into account by considering the local structures of the ligand octahedron around the V 4+ due to the JahnTeller eect. Based on the calculations, the ligand octahedra around V 4+ are suggested to suer 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 hyperne structure constants A and A ⊥ for V 4+ centers in MB4O7 glasses were suggested in the discussion.
The electron paramagnetic resonance (EPR) parameters (g factors g x , g y , g z and hyperfine structure constants A x , A y , A z ) for Cu 2+ in (NH 4 ) 2 Mg(SO 4 ) 2 ·6H 2 O (DHMS) crystal are theoretically investigated using the high-order perturbation formulas of these parameters. In the calculations, the ligand orbital and spin-orbit coupling for the impurity Cu 2+ are taken into account; the required crystal-field parameters are estimated from the superposition model which enables correlation of the crystal-field parameters and hence the EPR parameters with the local structure of the impurity center. The ligand orbital and the spinorbit coupling contributions are included on the basis of the cluster approach. Based on the calculation, the theoretical EPR parameters show good agreement with the observed values. The results are discussed.
Based on the defect model that the impurity Cu 2+ in TiO 2 on the octahedral Ti 4+ site is associated with one oxygen vacancy V O along the C 2 axis, the electron paramagnetic resonance (EPR) parameters, i. e., the g factors g i (i = x, y, z) and the hyperfine structure constants A i , of the Cu 2+ -V O center in TiO 2 are calculated by using the perturbation formulas of these parameters for a 3d 9 ion in a rhombically elongated octahedra. From this study, the impurity Cu 2+ is found to be away from V O by a distance ∆z (≈ 0.33Å) along the C 2 axis, meanwhile the four O 2− ions in the plane perpendicular to the C 2 axis may be shifted by ∆x (≈ 0.28Å) towards V O due to the electrostatic interaction between these ions and V O . The theoretical results based on the above local structure distortions show good agreement with the experimental data.
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 3 C 6 H 5 O 7 · 2H 2 O 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 trisodium citrate dehydrate single crystal can be obtained.
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 ≈ 1.91 Å, 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.
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