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Electron Paramagnetic Resonance (EPR) spectroscopic studies of VO 2+ ions as paramagnetic impurity in Lithium Sodium Acid Phthalate (LiNaP) single crystal have been done at room temperature on X-Band microwave frequency. The lattice parameter values are obtained for the chosen system from Single crystal X-ray diffraction study. Among the number of hyperfine lines in the EPR spectra only two sets are reported from EPR data. The principal values of g and A tensors are evaluated for the two different VO 2+ sites I and II. They possess the crystalline field around the VO 2+ as orthorhombic. Site II VO 2+ ion is identified as substitutional in place of Na 1 location and the other site I is identified as interstitial location. For both sites in LiNaP, VO 2+ are identified in octahedral coordination with tetragonal distortion as seen from the spin Hamiltonian parameter values. The ground state of vanadyl ion in the LiNaP single crystal is d xy . Using optical absorption data the octahedral and tetragonal parameters are calculated. By correlating EPR and optical data, the molecular orbital bonding parameters have been discussed for both sites. [ABSTRACT FROM AUTHOR]

Cu(II) ion-doped NaCaAlPO4F3 phosphor has been synthesized using a solid state reaction method. The prepared sample is characterized by powder X-ray diffraction, scanning electron microscope, optical absorption, electron paramagnetic resonance photoluminescence and Fourier transform infrared spectroscopy techniques. The crystallite size evaluated from x-ray diffraction data is in nanometers. Scanning electron microscopy micrographs showed the presence of several irregular shaped particles. From optical absorption and electron paramagnetic resonance spectral data the doped Cu(II) ions are ascribed to distorted octahedral site symmetry. The synthesized phosphor exhibits emission bands in ultraviolet, blue and green regions under the excitation wavelength of 335 nm. The CIE chromaticity coordinates (x = 0.159, y = 0.204) also calculated for the prepared sample from the emission spectrum. The Fourier transform infrared spectroscopy spectrum revealed the characteristic vibrational bands of the prepared phosphor material. [ABSTRACT FROM AUTHOR]

Abstract: Electron paramagnetic resonance (EPR) study of Cu2+ doped bis (glycinato) Mg (II) monohydrate single crystals is carried out at room temperature. Copper enters the lattice substitutionally and is trapped at two magnetically inequivalent sites. The observed spectra are fitted to a spin-Hamiltonian of rhombic symmetry with the following values of the parameters: Cu2+ (I), g x =2.1577±0.0002, g y =2.2018±0.0002, g z =2.3259±0.0002, A x =(87±2)×10−4 cm−1, A y =(107±2)×10−4 cm−1, A z =(141±2)×10−4 cm−1; Cu 2+ (II), g x =2.1108±0.0002, g y =2.1622±0.0002, g z =2.2971±0.0002, A x =(69±2)×10−4 cm−1, A y =(117±2)×10−4 cm−1and A z =(134±2)×10−4 cm−1. The ground state wave function of the Cu2+ ion in this lattice is evaluated to be predominantly |x 2 − y 2 :italic>g-factor anisotropy is also calculated and compared with the experimental value. With the help of the optical absorption study, the nature of bonding in the complex is discussed. [Copyright &y& Elsevier]

Abstract: X-Band electron paramagnetic resonance (EPR) studies of Gd3+ ions in ammonium hydrogen malonate single crystals have been done at room temperature. Detailed EPR analysis indicates the presence of four physically equivalent but magnetically inequivalent sites. The zero-field splitting parameters and g factor are determined. The Gd3+ ion is in 8S state; its levels are split by the action of the crystalline electric field of monoclinic symmetry. The optical absorption spectra of Gd3+ ions in single crystals of ammonium hydrogen malonate are also recorded at room temperature. The energy levels of the 4f7 configuration are calculated and compared with those observed experimentally. The values of E 1=5854±11, E 2=31±0.36, E 3=592±3.3 and ζ4f=1595±25cm−1 are found to give the best over-all agreement between experimentally observed and calculated levels. [Copyright &y& Elsevier]

Abstract: Electron paramagnetic resonance (EPR) study of VO2+ doped zinc potassium phosphate hexahydrate single crystal is carried out. The angular variation of the spectra is studied in the three crystallographic planes. The principal value of spin Hamiltonian parameters g and A and the direction cosines which principal axes make with the crystallographic axes are determined. The observed values are site I: g ∥=1.9664±0.0002, g ⊥=1.9973±0.0002, A ∥=150±2×10−4, A ⊥=60±2×10−4 cm−1; site II: g ∥=1.9276±0.0002, g ⊥=1.9921±0.0002, A ∥=155±2×10−4 and A ⊥=62±2×10−4 cm−1. By comparison of direction cosines of g from EPR with the direction cosines of different bonds obtained from crystal structure data it is ascertained that the VO2+ ion occupies Zn2+ substitutional sites. The optical absorption study of the crystal at room temperature is also carried out. The bands observed in the optical absorption spectrum are attributed to d–d transitions. The EPR results together with the optical data are employed to estimate the molecular orbital (MO) coefficients. These MO coefficients (also called bonding coefficients) are further used to discuss the nature of bonding of VO2+ ion with different ligands in the crystal. [Copyright &y& Elsevier]

Abstract: The local structure around Cu2+ ion has been examined by means of electron paramagnetic resonance and optical absorption measurements in xK2O–(40−x)Na2O–50B2O3–10As2O3 (0⩽x⩽40) glasses. The site symmetry around Cu2+ ions is found to be tetragonally distorted octahedral and the ground state of Cu2+ is . The spin-Hamiltonian parameter g || goes through a minima whereas goes through a maxima around R K=0.5, showing the mixed alkali effect. The glass exhibited broad absorption band centred 12,239cm−1 corresponding to the transition 2B1g→2B2g. By correlating the EPR and optical absorption data, the molecular orbital coefficients α2 and are evaluated for the present glass system. The IR studies show that the glass system contains BO3 and BO4 units in the disordered manner. [Copyright &y& Elsevier]

Abstract: Electron paramagnetic resonance (EPR) and optical absorption studies of VO2+ doped lithium potassium sulphate single crystals are carried out at room temperature. The angular variation of the spectra is studied in the crystallographic a*b, bc and ca* plane. Vanadyl is found to have fixed orientations in the lattice and there are two magnetically inequivalent complexes in the lattice. The spin Hamiltonian parameters obtained from single crystal data for the two sites are, Site I: gxx =2.0015±0.0002, gyy =1.9835±0.0002, gzz =1.9211±0.0002, Axx =(48±2)×10−4 cm−1, Ayy =(64±2)×10−4 cm−1, Azz =(169±2)×10−4 cm−1, Site II: gxx =2.0019±0.0002, gyy =1.9796±0.0002, g zz =1.9225±0.0002, Axx =(48±2)×10−4 cm−1, Ayy =(83±2)×10−4 cm−1, Azz =(178±2)×10−4 cm−1. The first three bands observed in optical absorption spectrum are attributed to d–d transitions and the last band is probably charge transfer band. The band positions are calculated using energy expressions and compared with the observed values to confirm the transitions. Crystal field parameter (D q) and tetragonal parameters (D s and D t) are also evaluated. Using EPR and optical results, the molecular orbital parameters of VO2+ ions in the lattice are evaluated with a tetragonal symmetry approximation (because the rhombic part is small) and the nature of bonding in the complex is discussed. [Copyright &y& Elsevier]

Abstract: X-band electron paramagnetic resonance (EPR) studies of VO2+ ions in sodium citrate single crystals have been done at room temperature. Detailed EPR analysis indicates the presence of two magnetically inequivalent VO2+ sites. Both the vanadyl complexes are found to take up substitutional position. The angular variation of the EPR spectra in three planes ba*, bc and ca* are used to determine principal g and A tensors. For the two sites the spin Hamiltonian parameters are, Site I: g x =1.9680, g y =2.0053, g z =1.9124, A x =79, A y =76, A z =185; Site II: g x =1.9650, g y =2.0067, g z =1.9418, A x =78, A y =70, A z =186×10−4 cm−1. The optical absorption study is also carried out at room temperature and absorption bands are assigned to various transitions. The theoretical band positions are obtained using energy expressions and a good agreement is found with the experimental values. By correlating EPR and optical data different molecular orbital coefficients are evaluated and the nature of bonding in the crystal is discussed. [Copyright &y& Elsevier]

Abstract: EPR study of copper ions in diglycine calcium chloride tetrahydrate (DGCCT), [(NH2CH2COOH)2·CaCl2·4H2O] single crystals at room temperature is carried out. The spin Hamiltonian parameters of copper ions are determined as: g x =2.0238±0.0002, g y =2.1122±0.0002, g z =2.2250±0.0002, A x =(83±2)×10−4 cm−1, A y =(86±2)×10−4 cm−1 and A z =(118±2)×10−4 cm−1. The optical study of the single crystals at room temperature is also done and the bands are assigned to d-d and charge transfer transitions. Using above data, the nature of bonding in the complex is discussed. [Copyright &y& Elsevier]

Abstract: X-Band electron paramagnetic resonance (EPR) studies of VO2+ ions in l-asparagine monohydrate single crystals have been done at room temperature. Detailed EPR analysis indicates the presence of two magnetically inequivalent VO2+ sites. Both the vanadyl complexes are found to take up interstitial position. The angular variation of the EPR spectra in three planes ab, bc and ca are used to determine principal g and A tensors. For the two sites the spin Hamiltonian parameters are, site I: g x =1.9633, g y =2.0274, g z =1.9797, A x =88, A y =61, A z =161×10−4 cm−1; site II: g x =1.9627, g y =1.9880, g z =1.9425, A x =90, A y =66, A z =167×10−4 cm−1. The optical absorption study is also carried out at room temperature and absorption bands are assigned to various transitions. The theoretical band positions are obtained using energy expressions and a good agreement is found with the experimental values. By correlating EPR and optical data different molecular orbital coefficients are evaluated and the nature of bonding in the crystal is discussed. [Copyright &y& Elsevier]

Abstract: EPR study of Cr3+-doped ammonium lithium sulphate single crystals is carried out at room temperature. The crystal field and spin Hamiltonian parameters are evaluated from the resonance line positions of different lines observed in the EPR spectra. The spin Hamiltonian parameters are found to be g=2.0003±0.0002, D=(269±2)×10−4 cm−1 and E=(82±2)×10−4 cm−1 for site I and g=1.9904±0.0002, D=(251±2)×10−4 cm−1 and E=(79±2)×10−4 cm−1 for site II, respectively. EPR data indicate that the site symmetry of Cr3+ ion in the crystal is distorted octahedron and it enters the lattice substitutionally replacing sites and bind to the neighbouring extra Li+ vacancies necessary for charge compensation. From optical study, the energy values of different orbital levels are estimated. Further, the bonding parameters are obtained by correlating optical and EPR data and the nature of bonding in the crystal is discussed. The values of Racah parameters (B and C), crystal field parameter (Dq) and nephelauxetic parameters (h and k) are obtained to be B=908, C=3553, Dq=1974cm−1, h=0.052 and k=0.21. [Copyright &y& Elsevier]

Abstract: Studies of fine and hyperfine structures of paramagnetic resonance spectra in single crystals of Mn2+: tetramethylammoniumtetrachlorozincate are reported. As sufficient numbers of lines were not obtained at room temperature, measurements were done at liquid nitrogen temperature (77K). The Mn2+ spin Hamiltonian parameters are evaluated employing a large number of resonant line positions observed for various orientations of the external magnetic field. The values of the zero field parameters that give good fit to the observed EPR spectra are obtained. The values of different parameters are: g =1.9834±0.0002, =(105±2)×10−4 cm−1, =(100±2)×10−4 cm−1, D =(349±2)×10−4 cm−1, E =(106±2)×10−4 cm−1 and a =(21±1)×10−4 cm−1. The percentage of covalency of the metal–ligand bond has also been determined. From the optical absorption study, the lattice distortion is suggested. The observed bands are assigned as transitions from the 6A1g(S) ground state to various excited quartet levels of Mn2+ ion in a cubic crystalline field. The electron repulsion parameters (B and C) and crystal field parameters (D q and α) providing a good fit to the observed optical spectra are evaluated and the values are: B =737cm−1, C =2322cm−1, D q =670cm−1 and α =76cm−1. The considerable decrease in the values of B and C parameters from free ion values (B =960cm−1, C =3325cm−1) has indicated that there exists a fair amount of covalent bonding between the central metal ion and the ligand. On the basis of deviations Δg = g −2.0023 it has been ascertained whether electrons are transferred to or from the central ion by the action of bonding. [Copyright &y& Elsevier]

Abstract: EPR and optical absorption studies of VO2+-doped zinc lactate trihydrate single crystals are done at room temperature. The EPR spectra of VO2+ are characteristic of tetragonally compressed octahedral site. The angular variation of the EPR spectra shows single site occupying interstitial position in the lattice. The spin Hamiltonian parameters are evaluated as gx =1.9771, gy =2.0229, gz =1.9236 and Ax =76, Ay =104, Az =197 (×10−4)cm−1. Using these parameters and optical absorption data various bonding parameters are determined and the nature of bonding in the complex is discussed. [Copyright &y& Elsevier]

Abstract: EPR study of Cr3+-doped tetramethyl cadmium chloride (TMCC) single crystals is carried out at room temperature. The crystal field and spin-Hamiltonian parameters are evaluated from the resonance line positions of different lines observed in the EPR spectra. The g and D parameter values are found to be g=1.9741±0.0002 and D=553±2×10−4 cm−1, respectively. EPR data indicate that the site symmetry of Cr3+ ion in the crystal is distorted octahedron. Cr3+ ions enter the lattice substitutionally replacing Cd2+ sites and bind to the neighboring extra Cd vacancies necessary for charge compensation. The optical absorption spectra are measured in 195–925nm wavelength range at room temperature. From optical study the energy values of different orbital levels are estimated. Further, the bonding parameters are obtained by correlating optical and EPR data and the nature of bonding in the crystal is discussed. The values of Racah parameters (B and C), crystal field parameter (Dq) and nephelauxetic parameters (h and k) are obtained to be B=722, C=2845, Dq=2043cm−1, h=1.015 and k=0.21. [Copyright &y& Elsevier]

Pure and copper doped glasses with composition, xLi2O-(40-x)Na2O-50B2O3 -10Bi2O3, have been prepared over the range 0 ≤ x ≤ 40. The electron paramagnetic resonance (EPR) spectra of Cu2+ ions of these glasses have been recorded in the X-band at room temperature. Spin Hamiltonian parameters have been calculated. The molecular bonding coefficients, α2+ and β2+, have been calculated by recording the optical absorption spectra in the wavelength range 200--1200 nm. It has been observed that the site symmetry around Cu2+ ions is tetragonally distorted octahedral. The density and glass transition temperature variation with alkali content shows non-linear behaviour. The IR studies show that the glassy system contains BO3 and BO4 units in the disordered manner. [ABSTRACT FROM AUTHOR]

Abstract: Optical and EPR investigations of chromium and nickel doped zinc phosphate glasses are carried out at room temperature to evaluate crystal field, spin-Hamiltonian and bonding parameters. For Cr3+ ion, the site symmetry is ascribed to a distorted octahedron, whereas the Ni2+ ion is located in a near octahedral site. In addition, the bonding parameters suggest covalent nature for Cr3+ and a moderate covalent nature for Ni2+ in the zinc phosphate glasses. [Copyright &y& Elsevier]

Optical absorption and EPR spectra of Co2+ and Ni2+ doped sodium phosphate glasses have been investigated. Crystal field parameters and g values are determined. For Co2+ doped glass Dq=890, B=700, C=4125 cm-1 and g values of 4.23 and 2.04 at 20 K, for Ni2+ doped glass Dq=890, B=770, C=3700 cm-1 and a g value of 2.28 at room temperature were found. Correlating the optical and electron paramagnetic resonance data suggests the bonding between transition metal ions and ligands as ionic in nature. [Copyright &y& Elsevier]

Vanadium and copper doped sodium phosphate glasses are prepared. EPR and optical absorption investigations are carried out. The results and analysis of the copper doped glass indicate that the copper ions enter the glass matrix as Cu2+ ions. The Cu2+ ion spectra are characteristic of tetragonally elongated octahedral site. The spectra of vanadium doped glass are characteristic of VO2+ and because of the short V&z.dbnd6;O band the distortion appears to be a tetragonally compressed one. Crystal field and spin-Hamiltonian parameters are evaluated. The bonding parameters indicate that bonding between the metal ions and ligands is partially covalent. [Copyright &y& Elsevier]