K.V. Narasimhulu

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.

A SINGLE CRYSTAL EPR STUDY OF VO2+ IONS DOPED IN CS2CO(SO4)2.6H2O TUTTON SALT

Abstract EPR spectra of VO2+ ions doped in single crystals of Cs2Co(SO4)2.6H2O single crystals have been studied at various temperatures (390–103 K) on X-band frequency. The detailed EPR analysis shows three vanadyl complexes with differing intensities. The g and A tensors are found to be axially symmetric. The intense vanadyl complexes in the lattice are found to occupy the Co2+ substitutional sites, whereas the weak vanadyl complex at the interstitial sites. The optical absorption spectrum at room temperature shows three absorption bands characteristic of VO2+ ions in tetragonal symmetry. By correlating the EPR and optical data, the molecular bonding coefficients and the Fermi contact interaction terms have been evaluated and discussed. The line broadening of VO2+ spectra on cooling the crystal is explained on the basis of spin-lattice relaxation narrowing. The spin-lattice relaxation time for the host Co2+ ions has been estimated at various temperatures.

Structural studies of marine exoskeletons: redox mechanisms observed in the Cu-supported CaCO3 surfaces studied by EPR

Electron Paramagnetic Resonance (EPR), optical and infrared (IR) spectral studies have been performed on the pure and Cu-adsorbed exoskeletons of marine environment. The EPR spectrum of exoskeletons at room temperature exhibits a sharp signal at g approximately 1.9970. The possible redox mechanisms have been noticed on heating these exoskeletons in which the low spin Mn(3+) reduces to Mn(2+). The optical absorption spectra also give the evidence of the presence of Mn(3+) ions. The effects of thermal sintering on the EPR spectra have been studied and discussed in detail. The Cu-adsorbed samples clearly showed the adsorption of the Cu(2+) ions over CaCO(3) and the redox mechanism in these samples have been monitored by EPR.

Electron paramagnetic resonance and optical absorption studies of Cu(II) ions in cadmium malate pentahydrate single crystals

Abstract The X-band electron paramagnetic resonance (EPR) studies on a single crystal of Cu(II) ion doped in cadmium malate pentahydrate have been studied over an extended temperature range of 120–390 K. The detailed analysis of EPR spectra reveal that the Cu(II) ion enters the Cd(II) site in the host lattice. From the observed EPR spectrum, the spin-Hamiltonian parameters have been evaluated. The optical absorption spectrum exhibits a broad band and a shoulder which are assigned to the transitions 2 B 1g → 2 B 2g and 2 B 1g → 2 E g respectively. The ground state wavefunction of Cu(II) at room temperature is evaluated.