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Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 68-11, Section: B, page: 7404. Adviser: J. Gary Eden. Includes bibliographical references (leaves 87-91) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--Lehigh University, 2007.

Thesis (Ph.D.)--Lehigh University, 2008. / Adviser: John Huennekens.

Several different methods for the gas phase assay of tritium have been investigated and a simple and rapid assay technique has been developed. This method has been used to measure the partial pressure of water in aqueous dioxan solutions at 18°C and at 25°C, in a concentration range where the partial pressures are too low to be readily measured by other methods. Partial excess thermodynamic functions of mixing have been calculated from the pressure measurements.

A preliminary investigation of a new Localised Molecular Orbital (LMO) method is presented and applied to the molecules HCN, CO, N2, H2O, NH3 and CH4. The LMOs are called Perfectly Localised Molecular Orbitals (PLMOs) and are obtained in the one-determinant Hartree-Fock Molecular Orbital-Linear Combination of Atomic Orbitals (MO-LCAO) approximation in a minimal AO basis. The PLMOs are obtained from a starting set of occupied Canonical Molecular Orbitals (CMOs) by applying a general orthogonal transformation to the sigma valence CMOs and by minimising the energy sacrificed in restricting the transformed MOs to basis AOs on one and two centres only. The atomic centres upon and between which the lone pair and bond PLMOs reside is decided largely by an energy criterion alone. The resulting set of PLMOs are non-orthogonal. In the example molecules, the energy difference between the canonical wave function and that constructed from the PLMOs is found to be small. The PLMOs, expressed in terms of normalised hybrid atomic orbitals (HAOs) on each atom, are found to reflect a normal valence description of the molecules in which the overall level of hybridisation is low. This is possible because a substantial degree of non-orthogonality among the HAOs on each atom is found. The PLMOs yield satisfactory bond and lone pair moments and electronic populations, and are also shown, to have a satisfactory behaviour at non-experimental geometries of the water molecule. It is concluded that the small sacrifice in accuracy that results from completely localising LMOs by the PLMO method is outweighed by the advantages of dealing with one and two-centre LMOs. It is also suggested that the differences in the properties of LMOs generated by different orthogonal transformation criteria is dependent on the relative amounts of delocalisation from bond and lone pair LMOs.

205Ti NMR relaxation and self-diffusion measurements were applied to study the probe qualities of thallium cations in sucrose/solvent systems. The value of variable field/variable temperature relaxation measurements in defining relaxation behaviour was demonstrated. The relaxation of the dimethylthallium(III) cation in 60% sucrose/D20 (w/w) solution is dominated by the GSA mechanism at both high and low field. It was necessary to use a temperature dependent Fuoss-Kirkwood distribution of correlation times to rationalise the R1 data and this analysis gave the shielding anisotropy of the cation as 5588 +/- 173ppm, in keeping with previous studies. Similar behaviour was noted for the diethylthallium cation in sucrose/DMSO-d6 solutions (>10% concentration) and a concentration dependence in the distribution width parameter was observed. The 13C relaxation in aqueous sucrose solution at 60% concentration similarly showed complex behaviour. Self-diffusion and relaxation studies on thallium(I) ion in sucrose/D2O solutions showed the cation to be a good diffusional probe in viscous solutions, but a poor probe of reorientational motion. Studies on the self-diffusion of the dimethylthallium(III) cation in D20 were consistent with a solvent structure - limited model for translational motion. Further studies in sucrose/D20 solutions showed the dimethylthallium(III) cation to be limited to studying solutions 30% concentration. Studies of Ti(I)+ ion in aqueous TANOL solutions showed an inverse frequency dependence of R1 and R2 and a dominant electron-nuclear scalar relaxation mechanism was proposed. Finally, 205Ti and 203Ti R1 measurements in neat and diluted thallium(I) ethoxide showed that in the neat solution the rates for both nuclei were equal at high field and were dominated by the GSA mechanism. At low field, 203Ti R1 > 205Ti and a dominant scalar mechanism was proposed. In dilute solution the rates were equal at both high and low field and no GSA contribution was observed.

Electro-rheological (ER) fluids, which are dispersions of solid particles in a non-conducting oil, have been studied for the first time at a molecular level using magnetic resonance spectroscopic techniques. The group of fluids on which measurements were first made was the already widely used lithium polymethacrylate dispersed in 20 cs silicone oil. The problems associated with this fluid such as high conductivity, relatively low viscosity changes, and settling out of the solid particles, led to fluids containing zeolites also to be investigated. Mechanical tests were performed on all these fluidsincluding static yield stresses measured at zero shear rate,and then a new electroviscometer was designed and built totest fluid performances in the shear rate range from 1.5 to 43.8 s and temperatures from +5 to +60 C.NMR relaxation measurements were used to study themobilities of the water and the ions in all these solids toinvestigate the relationship between these properties, and the performance of a solid as a constituent in an ER fluid. This is the first time that many of these systems have been studied in this way. ESR was used to study the motion of spin probe radicals in partially hydrated zeolites for the first time. The effect of an electric field on the motion of the spin probe inside a zeolite particle was measured and decreased motion was observed as the strength of the electric field wasincreased in those zeolites which showed a significant EReffect, while no effect on the probe motion was seen for those zeolites which constituted a weak ER fluid. The first saturation transfer ESR experiments have been performed on spin probes inside partially hydrated zeolites that previously had been out of the motional range of conventional CWESR, and the anisotropy of the probe motion has been highlighted.