107 leaves : ill., appendices / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics, 1970

Thesis (Ph.D.) -- University of Adelaide, Dept. of Physics, 1970.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1983. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1960. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 56-58).

Thesis (M.S.) OGI School of Science & Engineering at OHSU, September 2007. / Includes bibliographical references (leaves 72-74).

Electron paramagnetic resonance techniques have been used to investigate the nature and possible effects of adsorption of gaseous species on several adsorbents, in particular several synthetic zeolites, at temperatures from 77°K upwards. Analysis of the spectra obtained has been aided through computer simulation of the various spectra and comparison of these to the actual observed spectra. The molecule chlorine dioxide ( C10₂ ) has been studied in various low temperature matrices but little has been published for C10₂ in the adsorbed state. An attempt was made to find an adsorbent such that an inert matrix might be approximated, to give a base from which to make comparisons. To this end, adsorbents including silica gel, synthetic zeolites 13X, 10X, 4A, 5A, Na-mordenite and H-mordenite were investigated. The results vary between those from silica gel, where spectra yielding EPR parameters similar to other matrices were obtained, to those from 13X where it was evident that two distinct adsorption sites of the C10₂ were present. In the 13X as in the other synthetic zeolites, EPR parameters markedly different from other studies were found and were attributed to the intense electrostatic fields present in these zeolites. Results obtained at room temperature for these adsorbents ranged from C10₂ molecules freely rotating in the cages of the zeolites to other molecules having hindered rotations. Nitrogen dioxide ( NO₂ ) was also investigated with a view to finding similar interactions. Although changes as marked as for C10₂ compared to other studies were not observed, the synthetic zeolite H-mordenite yielded spectra closely approximating those obtained in solid N₂O₄ matrices. It is proposed the NO₂ molecules are caged in the numerous side pockets emanating from the main channels in this zeolite and are effectively isolated from other NO₂ molecules. The resulting spectra are strikingly more resolved than those obtained using other adsorbents and enabled accurate computer simulations to be made. The adsorption of nitric oxide ( NO ) produced an effect not found with the other molecules. A new species was formed from a reaction of the NO with H-mordenite and could not be removed at room temperature, indicating a strong bond to the surface. The new species does not contain nitrogen as identical spectra were obtained from adsorption of ¹⁴NO and ¹⁵NO. Attempts to observe spectra which could be assigned to the difluoroamino radical from adsorption of tetrafluorohydrazine were unsuccessful. The spectra observed were assigned to a species having no hyperfine structure and an anisotropic g tensor. / Science, Faculty of / Chemistry, Department of / Graduate

Paramagnetic impurities containing oxygen were produced in the reactions of KBr, KCl, NaCl and SrCl(2) with fluorine. Molecular oxygen, FOO･ radical and C10(2) were identified by ESR as reaction by-products. The spectra assigned to CIO(2) have predominant powder character even in single crystals of halides. The results are correlated with previous work in this laboratory. The origin of oxygen impurity is suggested to be surface hydroxide ions in KBr and KC1, and entrapped water in NaCl and SrCl(2). Nucleation processes and other anomalous features observed in these reactions by previous workers are explained by the presence of impurities. Oxygen was found to be incorporated into the SrCl(2) crystals by recrystallisation from the melt in the presence of oxygen. It exists in the form of superoxide ion O(2)¯ which occupies an interstitial position between two lattice anions and is associated with two anion vacancies. The molecular axis lies in a [00l] direction of the crystal and the degeneracy of the 2pπ(g) -molecular orbital is lifted by the crystal field. The bonding between the O(2)¯ ion and its neighbouring cations and anions is discussed in terms of a Cl(6)Sr･O(2)¯･SrCl(6) "complex". The orbital angular momentum reduction factor for O(2)¯ in SrCl(2) has been calculated from the experimental g-factors and found to be anomalously large. A survey was made on impurities incorporated into strontium compounds through processes of recrystallisation from melts or from aqueous solutions. Strontium carbonate was identified in melt-recrystallised Sr(NO3)(2) by Infrared Spectroscopy and X-ray powder method. It was produced by partial decomposition of the nitrate in the presence of atmospheric CO(2). NO(3)²¯ ion was identified in the recrystallised material by ESR. ESR and infrared studies suggest that the NO(3)²¯ ion substitutes a carbonate ion in the SrCO(3) lattice. Results from a similar study on Ba(NO3)(2) also support this conclusion. / Science, Faculty of / Chemistry, Department of / Graduate

X-irradiated cyanoacetylurea CNCH₂CONHCONH₂ and x-irradiated dicyandiaraide NCNC(NH₂)₂ single crystals were studied,by Electron Spin Resonance. Two radical species were formed when cyanoacetylurea, CNCH₂CONHCONH₂, was irradiated with x-rays. One was a π-electron radical, CNCHCONHCONH₂, and the other a σ-electron radical, CNCH₂CONHCONH . The σ electron radical was found to have a large, isotropic proton coupling tensor and an anisotropic nitrogen coupling tensor very similar to those of H₂NCOCH₂CONH . The π-electron radical had similar proton and nitrogen coupling tensors as CNCHCOOH which was formed in γ-irradiated cyanoacetic acid. In x-irradiated dicyandiamide crystals, the main species formed was shown to be NCNC(NH₂)NH, having also a large, isotropic proton coupling tensor, and hyperfine interactions with two nitrogen coupling nuclei were also observed and measured. ESR studies were carried out both at room and at liquid nitrogen temperatures. The effect of temperature on the spectra is discussed. INDO-SCF-LCAO-MO calculations were carried out for a model compound HCONH , with the amide proton assuming different inplane and out of plane positions. The spin density was found to vary over a wide range and could be used to interpret the large proton coupling of the dicyandiamide radical. MO calculations were also performed on the radical NCCHCOO ̄. The calculated results correlate fairly satisfactorily with the observed ones. Comparison of the direction of the unpaired electron p-orbital symmetry axis with bond directions and with normals to the fragment planes showed that while malonamide radical, H₂NCOCH₂CONH was a genuine σ-electron radical, dicyandiamide radical, NCNC(NH₂)NH was most likely a π-electron radical. / Science, Faculty of / Chemistry, Department of / Graduate

The e.p.r. spectrum for relatively dilute samples of phosphorus-doped silicon (<5 x 10(16) donors/cm³) has been calculated in detail for an assumed random distribution of impurities. The system of donor electron spins is treated as a collection of nearest neighbor donor pairs. An expression is derived for the donor pair exchange energy using Kohn-Luttinger wavefunctions and a general exchange energy expression. The resultant relationship contains an adjustable parameter a*, the "effective Bohr radius", which is determined from a comparison of the calculated spectrum and the experimental results obtained for the ratio, C, of the "central pair" and "hyperfine" line intensities. The resulting expression J(R), where J represents the exchange energy and R the separation vector connecting the two pair donors, exhibits an oscillatory spatial dependence due to interference from portions of the wavefunction arising from different conduction band valleys. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A completely general method has been developed for calculating Electron Paramagnetic Resonance (EPR) transition fields and transition probabilities from the spin Hamiltonian [formula omitted] The method is a generalization of a previously existing, limited technique, and can be applied without any restrictions. A general computer program has also been written based on the method. Using the program, the results of an EPR study on a U.V. irradiated single crystal of para-nitrophenyl azide were fitted to the spin Hamiltonian [formula omitted] The observed and calculated fine and hyperfine transition probabilities were found to be in good agreement. The observed hyperfine splittings, due to the nitrene nitrogen, were analyzed in terms of a 6.5 gauss linewidth, combined with the transition probabilities for the nine theoretical components of the hyperfine resonance fields. Evidence of a ¹⁴N quadrupolar splitting was observed, but not completely analyzed. In addition, evidence was found to indicate that the nitrene impurity is twisted somewhat from the position in the crystal lattice held by the parent azide. The EPR spectra obtained on U.V. irradiation of randomly oriented 1,5- and 1,8-diazidonaphthalene were analyzed, and found to originate from ground triplet state species with |D|= 0.8152±0.0010 cm⁻¹ and 0.7599±0.0010 cm⁻¹, respectively. The theoretical spin densities for the triplet and quintet states of 1,5- , 1,8- and 2,7- naphthalene dinitrene were calculated using the method of intermediate neglect of differential overlap (INDO). Attempts to obtain a consistent picture of multiplet spin densities based on the results of the calculations were largely inconclusive. / Science, Faculty of / Chemistry, Department of / Graduate