N.O. Gopal

EPR and IR spectral investigations on some leafy vegetables of Indian origin

EPR spectral investigations have been carried out on four edible leafy vegetables of India, which are used as dietary component in day to day life. In Rumex vesicarius leaf sample, EPR spectral investigations at different temperatures indicate the presence of anti-ferromagnetically coupled Mn(IV)-Mn(IV) complexes. EPR spectra of Trigonella foenum graecum show the presence of Mn ions in multivalent state and Fe(3+) ions in rhombic symmetry. EPR spectra of Basella rubra indicate the presence of Mn(IV)-O-Mn(IV) type complexes. The EPR spectra of Basella rubra have been studied at different temperatures. It is found that the spin population for the resonance signal at g=2.06 obeys the Boltzmann distribution law. The EPR spectra of Moringa oliefera leaves show the presence of Mn(2+) ions. Radiation induced changes in free radical of this sample have also been studied. The FT-IR spectra of Basella rubra and Moringa oliefera leaves show the evidences for the protein matrix bands and those corresponding to carboxylic CO bonds.

A Study of Electron Paramagnetic Resonance and Optical Absorption Spectra of VO2+ Ions in Alkali Barium Phosphate Glasses

The electron paramagnetic resonance and optical absorption spectra of VO2+ ions in different alkali barium phosphate glasses have been studied and the results have been analysed using C4v symmetry. The EPR spectrum shows eight hyperfine lines characteristic of VO2+ ions. From the observed EPR spectra, the spin-Hamiltonian parameters, Fermi contact interaction parameter k, dipolar hyperfine coupling parameter P have been evaluated. The EPR spectra exhibit a marked concentration dependence. The EPR spectra were also recorded at different temperatures. The number of spins participating in resonance is found to be increasing with decreasing temperature. The paramagnetic susceptibility χ is calculated from the EPR data. As the temperature decreases, χ increases in accordance with Curies law. The optical absorption spectrum exhibits two bands corresponding to the transitions 2B2g → 2B1g and 2B2g → 2Eg, characteristic of VO2+ ions in octahedral symmetry with tetragonal distortion. From the ultraviolet edges of these optical absorption spectra, the optical band gap energies (Eopt) of the glass samples have been calculated. The optical band gap energy varies with alkali content. By correlating EPR and optical absorption data, the molecular orbital coefficients have been evaluated. The theoretical values of optical basicity of the glasses have also been evaluated.

EPR and Optical Studies of Vanady Ions in Alkali Lead Borotellurite Glasses

Electron Paramagnetic Resonance (EPR) and optical absorption spectra of

EPR as an analytical tool in assessing the mineral nutrients and irradiated food products-vegetables

VO^{2+}

EPR and optical absorption studies on VO2+ ions doped in cobalt maleate tetrahydrate single crystals

ions in different alkali lead borotellurite glasses have been studied. The spin-Hamiltonian parameters (g and A), bonding parameter

EPR and optical investigations of manganese ions in alkali lead tetraborate glasses.

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EPR and optical absorption studies of Cu2+ ions in alkaline earth alumino borate glasses

and Fermi contact interaction parameter k have been calculated. The values of spin-Hamiltonian parameters confirm that the vanadyl ions are present in the glasses as

EPR and optical studies of Mn2+ ions in Li2O-Na2O-B2O3 glasses : An evidence of mixed alkali effect

VO^{2+}

EPR and optical absorption spectral studies of Cu2+ ions doped in alkali lead tetraborate glasses

molecular ions in an octahedral site with a tetragonal compression. The number of spins (N) participating in resonance is calculated as a function of temperature (123-393 K) for 9 mol% of

EPR and optical investigations of Eu2+-doped BaFCl phosphor

VO^{2+}