EPR and electronic absorption studies of the VO2+ ion in 3CdSO4·8H2O single crystals

Spectroscopic and structural characterization of pascoite

Pascoite mineral having yellow-orange colour of Colorado, USA origin has been characterized by EPR, optical and NIR spectroscopy. The colour dark red-orange to yellow-orange colour of the pascoite indicates that the mineral contain mixed valency of vanadium. The optical spectrum exhibits a number of electronic bands due to presence of VO(II) ions in the mineral. From EPR studies, the parameters of g, A are evaluated and the data confirm that the ion is in distorted octahedron. Optical absorption studies reveal that two sets of VO(II) is in distorted octahedron. The bands in NIR spectra are due to the overtones and combinations of water molecules.

EPR of vanadyl impurity in zinc ammonium trihydrogen bis(orthophosphate) monohydrate single crystal

The electron paramagnetic resonance spectroscopic investigation of VO(II)-doped zinc ammonium trihydrogen bis(orthophosphate) monohydrate single crystal has been carried out at 300K. The single crystal, rotated along the three orthogonally crystallographic axes, have yielded spin Hamiltonian parameters g and A as: g(xx)=1.978, g(yy)=1.974, g(zz)=1.925 and A(xx)=7.4, A(yy)=7.8, A(zz)=19.4 mT. These spin Hamiltonian parameters reflect a slight deviation from axially symmetry to rhombic, which is elucidated by the interstitial occupation of the vanadyl ion. The isofrequency plots and EPR spectra at few orientations have been simulated using the calculated spin Hamiltonian parameters. The Fermi contact parameter (kappa) and dipolar interaction parameter (P) have been calculated as 0.857 and -128 x 10(-4)cm(-1), respectively. The percentage of metaloxygen bond has been identified as 20%.

EPR and optical absorption studies of VO2+ doped L-arginine phosphate monohydrate single crystals--part I

The electron paramagnetic resonance (EPR) studies on VO2+ doped L-arginine phosphate monohydrate (LAP) single crystals at room temperature at X-band frequencies reveal the presence of two magnetically inequivalent VO2+ sites occupying interstitial positions in the lattice with fixed orientations and show very high angular dependence. The principal values of the g and A tensors indicate that the electrostatic field around the VO2+ ion is rhombic. The optical absorption spectra at room temperature show four absorption bands at 16155, 14775, 10928 and 10526 cm(-1), characteristic of rhombic symmetry. From EPR and optical absorption data, the molecular orbital bonding coefficients (beta2, epsilon2, P and k) and the crystal field parameters have been evaluated.

Single crystal EPR study of VO(II)-doped magnesium

Single crystal EPR studies of VO(II)-doped magnesium potassium Tutton's salt have been carried out at room temperature. The results indicate that the paramagnetic impurity has entered the lattice, both substitutionally and interstitially and the maximum hyperfine for the substitutional site along the a axis corresponds to the minimum hyperfine for interstitial site and vice versa. The spin Hamiltonian parameters obtained from single crystal data for these sites are: Site 1, gparallel = 1.954(1); gperpendicular = 1.998(1), Aparallel = 19.80(2) mT; Aperpendicular = 7.61(2) mT; Site 2, gparallel = 1.997(1); gperpendicular = 1.952(1), Aparallel = 7.66(2) mT; Aperpendicular = 19.85(2) mT. Superhyperfine from ligand protons have been observed at certain orientations for Site 2 impurity. Powder spectrum shows a set of eight parallel and perpendicular features indicating the presence of only one site and these values matched with Site 1 values. From these observations, it has been concluded that the two vanadyl impurities are approximately at right angles to each other. Cooling the sample to 77 K does not change the spectra appreciably. The admixture coefficients have been calculated from Site 1 data, which agree well with the reported values.