Department of Chemistry
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Item Magnetic resonance lineshapes in powdered and amorphous systems(IAS, 1986-04) Sivasubramanian, S.C.A survey is made of the theory and applications ofEPR andNMR absorption lineshapes observed in powdered and amorphous materials. The ‘spin Hamiltonian’ and ‘resonance condition’ formalisms are reviewed, andepr andnmr lineshapes are discussed which typify the singularity characteristics in powdered materials. In the amorphous or ‘glassy’ state, the measurable spin resonance parameters often have to be viewed as being ‘randomly distributed’ according to a probability density function. Several recent probability-theory based approaches to lineshape computation for modelling the amorphous state are discussed.Item X-ray diffraction, electron paramagnetic resonance, and electron spin echo modulation studies of the lead oxide-lead chloride-cupric chloride ternary glass system(ACS, 1991-08-01) Sivasubramanian, S.C.X-ray diffraction, EPR, and ESEM studies are reported for a novel ternary glass 43PbO-56PbCl2-1 CuCl2. The X-ray PDF data lead to a structural model in which octahedral building units of Cu04Cl2 are predominant. EPR spectra of the glass at X and Q bands have been fitted, by line shape simulation, to the distributed spin Hamiltonian parameters g^rnean) = 2.34, = 0.03, gx(mean) = 2.06, ± = 0.008, p = 0.95, /4,(mean) = 131.1 X 10"4 cm"1, and /4x(mean) = 5.8 X 10"4 cm"1. These data suggest a distribution of bonding geometries for Cu2+ in the glass structure, with the above-mentioned elongated octahedral Cu04Cl2 dominating. ESEM results suggest that Cu2+ may be surrounded by four Pb2+ in the second coordination shell at a distance of 3.8 ÁItem X-ray diffraction, electron paramagnetic resonance, and electron spin echo modulation studies of the lead oxide-lead chloride-cupric chloride ternary glass system(ACS, 1991-08-01) Sivasubramanian, S.C.X-ray diffraction, EPR, and ESEM studies are reported for a novel ternary glass 43PbO-56PbCl2-1 CuCl2. The X-ray PDF data lead to a structural model in which octahedral building units of Cu04Cl2 are predominant. EPR spectra of the glass at X and Q bands have been fitted, by line shape simulation, to the distributed spin Hamiltonian parameters g^rnean) = 2.34, = 0.03, gx(mean) = 2.06, ± = 0.008, p = 0.95, /4,(mean) = 131.1 X 10"4 cm"1, and /4x(mean) = 5.8 X 10"4 cm"1. These data suggest a distribution of bonding geometries for Cu2+ in the glass structure, with the above-mentioned elongated octahedral Cu04Cl2 dominating. ESEM results suggest that Cu2+ may be surrounded by four Pb2+ in the second coordination shell at a distance of 3.8 Á.