J. Lakshmana Rao

EPR and IR spectral studies of the sea water mussel Mytilus conradinus shells

The electron paramagnetic resonance (EPR) and infrared (IR) spectral studies have been employed on the periostracum, the prismatic layer and the nacre of the shell of the marine bivalve molluscan Mytilus conradinus of the South Indian origin. All the layers of this shell show Fe3+ ion spin resonance signals in common. The inner layer namely nacre at room temperature shows EPR signals of Fe3+ ions and the heated one exhibits a sextet hyperfine pattern characteristic of Mn2+ ions. The prismatic layer of the shell also exhibits a similar spectrum, but of distinct pattern. The spin-Hamiltonian parameters have been evaluated for the prismatic and nacreous layers of this shell. Infrared spectra of the two main layers of the shell namely prismatic and the nacre exhibit the characteristic bands of CO3(2-) molecular ion in different symmetries of CaCO3.

Electron paramagnetic resonance and optical absorption studies on vanadyl doped alkali tetraborate glasses

Abstract Electron paramagnetic resonance (EPR) and optical absorption studies have been made for VO(II) ions in alkali tetraborate glasses. The EPR spectrum shows eight hyperfine lines characteristic of VO(II) ions. The spin-Hamiltonian parameters, Fermi contact interaction parameter K , dipolar hyperfine coupling parameter P have been evaluated from the spectra. The anisotropy energy of the VO(II) ions have also been calculated. The values of the spin-Hamiltonian parameters confirm that V 4+ ions are present in the glasses as VO(II) molecular ions in an octahedral site with a tetragonal compression. The theoretical values of optical basicity (^ th ) of glasses have also been evaluated. The optical absorption spectra of VO(II) ions in these glasses show two bands corresponding to the transitions 2 B 2g → 2 B 1g and 2 B 2g → 2 E g in the order of decreasing energy respectively. By correlating the electron paramagnetic resonance data and optical data, the molecular orbital coefficients have been evaluated.

EPR and optical studies of vanadyl ion in magnesium thallium sulphate hexahydrate

Abstract Results of EPR and optical studies of vanadyl ion (VO2+) doped in magnesium thallium sulphate hexahydrate are reported. The spin-Hamiltonian parameters are determined from the powder EPR spectra at room temperature. The optical absorption spectra at room and liquid nitrogen temperatures have also been studied. By correlating the EPR and optical spectral data, the molecular orbital bonding parameters have been evaluated.

Electron paramagnetic resonance and optical absorption spectra of fresh water mussel Lamellidens marginalis shells

Abstract Electron Paramagnetic Resonance (EPR) and optical absorption spectra of fresh water mussel Lamellidens marginalis shells have been studied at room temperature (300 K). The EPR spectra exhibit a group of five fine structure transitions, characteristic of the Mn2+ion. From the observed spectra the spin-Hamiltonian and zero-field splitting parameters have been determined. The observed spin-Hamiltonian parameters are found to be very near to the parameters reported for aragonite like shells. The optical absorption spectrum exhibits bands characteristic of Mn2+ ions in octahedral symmetry. From the observed spectrum, the crystal field parameters were then evaluated.

Epr of cu2+ ions in synthetic NaNH4SO4.2H2O single crystals

Abstract Electron paramagnetic resonance spectra of Cu 2+ ion in NaNH 4 SO 4 .2H 2 O single crystals were studied between 300 and 77 K at the X-band. The angular variation spectra show that the Cu 2+ ions enter at the Na + site in the host lattice, exhibiting two symmetry-related equivalent complexes. The principal values of the A - and g -tensors are found to be axially symmetric and temperature dependent. The optical absorption band observed at ~ 11,800 cm −1 is assigned to the transition 2 B 1 g → 2 B 2 g . The molecular orbital bonding parameters were evaluated.

EPR and optical studies of vanadyl complexes in two host-crystals of Tutton salts of thallium

Abstract Electron paramagnetic resonance (EPR) and optical absorption spectra of vanadyl complexes in the two Tutton salts (Tl2Zn(SO4)2 · 6H2O and Tl2Mg(SO4)2 · 6H2O single crystals) have been studied between room temperature (300 K) and liquid nitrogen temperature (77 K). The vanadyl ion (VO2+) is found to substitute the host divalent cation sites. Three distinct vanadyl complexes have been identified. The spin Hamiltonian parameters have been calculated from the single crystal as well as the powder spectra. By correlating EPR and optical data, the molecular orbital bonding coefficients are determined.

Electron spin resonance and electronic absorption studies of magnesium thallium sulphate hexahydrate doped with Cu2+ ions

Abstract ESR and electronic absorption spectra of copper ion in magnesium thallium sulphate hexahydrate (MgTlSH) have been studied both at room and liquid nitrogen temperatures. The spin-Hamiltonian parameters and the molecular orbital coefficients have been evaluated. From the spectral analysis, it is found that the Cu2+ ions substitute for Mg2+ ions.

Electron paramagnetic resonance and optical absorption spectra of Mn2+ in magnesium malate pentahydrate (MMPH) single crystals

Abstract Electron paramagnetic resonance (EPR) and optical absorption spectra of Mn2+ ions doped in single crystals of magnesium malate pentahydrate (MMPH) have been studied between 300 and 120 K. The EPR spectra exhibit a group of five fine structure transitions, characteristic of Mn2+ ions. From the observed EPR spectra, the spin-Hamiltonian and zero-field splitting parameters have been determined. The observed spin-Hamiltonian parameters are found to be very near to the parameters reported for other carboxylic salts. Optical absorption spectrum exhibits bands characteristic of Mn2+ ions in distorted octahedral symmetry. From the observed spectrum, the crystal field parameters have been evaluated.

Electron paramagnetic resonance studies on Cu(II) ions doped in Tl2Ni(SO4)2·6H2O single crystals

Abstract The X -band electron paramagnetic resonance (EPR) studies on a single crystal of Cu(II) ions doped in thallium nickel sulphate hexahydrate have been made over an extended temperature range of 120 K to 390 K. Two chemically equivalent, but magnetically inequivalent Cu(II) complexes have been observed. The angular variation spectra reveal that the Cu(II) ion enters the Ni(II) site in the host lattice. From the observed EPR spectrum the spin-Hamiltonian parameters have been evaluated. The orbital reduction factor and covalency parameters are also evaluated. The optical absorption spectrum exhibits a broad band at 11,850 cm −1 which is assigned to the transition 2 B 1 g → 2 B 2 g .

Absorption Spectra of Co(II)Ions Doped in Magnesium Thallium Sulphate Hexahydrate

Abstract The optical obsorption spectrum of Co(II) ions doped in magnesium thallium sulphate hexahy drate is studied at room and liquid nitrogen temperatures. The crystal exhibits characteristic absorption of the Co(II) ion in the visible and near infrared. The observed bands are assigned to transitions from the ground state 4T1g (F) to various excited quartet and doublet levels of the Co(II) ion in octahedral symmetry. The splitting of one of the bands at liquid nitrogen temperature is explained to be due to spin-orbit splitting. All band positions have been fitted by the parameters B, C, Dq and ξ.