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Typescript. / Thesis (Ph. D.)--University of Hawaii, 1968. / Bibliography: leaves [131]-134. / xi, 134 l illus

Thesis (Ph. D.)--Montana State University--Bozeman, 2007. / Typescript. Chairperson, Graduate Committee: David J. Singel. Includes bibliographical references (leaves 114-122).

Thesis--University of Florida. / Description based on print version record. Typescript. Vita. Bibliography: leaves 171-172.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

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Hydrazoic acid has been photolysed in a krypton matrix at 4°K and the products studied by electron spin resonance spectrometry. This study showed that NH₂ radicals have been produced as a secondary product in the reaction. In addition a broad, intense resonance at g = 2 and a weak, half field resonance has been tentatively assigned to the imine (NH) radical. This suggestion is shown to be consistent with theoretical considerations. Diazomethane has also been photolysed in krypton and carbon monoxide matrices at 4°K, and the products studied by e.s.r., in an attempt to detect the methylene (CH₂) radical. The results of this study were complicated and a complete analysis was not possible. It is suggested that some of the features may be explained in terms of an overlap of the spectre from CH₃ and CH radicals. There are difficulties in such an explanation however. A study has been made on the line shapes of poly-crystalline samples of aromatic triplet state molecules. It is shown how the experimentally observed spectra of the photoexcited triplet states of axially symmetric molecules such as triphenylene and non-axially symmetric molecules such as naphthalene and phenanthrene can be explained in terms of a line shape calculated from a first order perturbation treatment. This model gives a good explanation of the observed line shapes, however better agreement with the observed field positions is obtained if a second order correction is included. Line shape calculations have also been made for molecules, such as the substituted imines, where spin-spin interaction is large. It is shown that the calculation is in agreement with the observed spectra of phenylimine and benzenesulfonylimine. In addition, it is shown how the experimentally determined value of the spin-spin interaction constant, D, can be related to the spin density on the nitrogen of the substituted imines. The spin densities calculated in this way are in good agreement with spin densities calculated on the basis of the Hückel theory. / Science, Faculty of / Chemistry, Department of / Graduate

The performance of a spin echo spectrometer which is suitable for chemical exchange studies is described. Using the Carr-Purcell sequence of pulses, proton T₂ values were obtained from two experiments differing only in their method of eliminating accumulated error in the width of the 180° pulses. The Meiboom-Gill method of phase shifting the r.f. in the first pulse is more flexible in the range of pulse intervals. Following the theory of Bloom, Reeves and Wells, rate constants describing the exchange process in two molecules were measured from the dependence of T₂ upon the pulse interval. The values of the rate constants for the hindered internal rotation about the N-N bond in N, N-dimethylnitrosamine agree with previous high resolution studies. A similar spin echo study has been conducted in order to measure the rates of internal rotation about the C-N bond in N, N-dimethylcarbamyl chloride. The values for the entropy of activation are consistently low. The possibility of systematic errors in the spin echo method has been investigated. It is concluded that reported values of rate constants in magnetic resonance should be the result of a spin echo investigation extending over as wide a temperature range as possible in addition to a high resolution study which involves a complete theoretical line shape fit to the experimental data. / Science, Faculty of / Chemistry, Department of / Graduate

The magneto-optical Faraday effect has been used to observe the spin-bath relaxation at low temperatures in CeES and in Eu-doped CaF₂. The paramagnetic Faraday rotation ϩ is an instantaneous measure of the magnetization M and it is shown that in CeES and Eu²+ : CaF₂, ϩ∾ M at the light frequencies employed. The apparatus is the same as that previously described by Rieckoff and by Griffiths. Pulsed MW-power at X-band has been used to disturb the equilibrium between spin system and bath. In CeES, the observed relaxation time Շ is of the order of a few msec, which is several orders of magnitude longer than the theoretical estimate of T₁. This suggests a severe bottleneck in the energy transfer spin-bath. Շis found to be environment-dependent. In HeII, the relaxation is exponential. Շ is in good agreement with nonresonant relaxation measurements by Van den Broek and Van der Marel. It is explained as arising from the Kapitza boundary resistance at the CeES-HeII interface. In HeI, the relaxation is non-exponential and is slower than in He gas at the same temperature. This suggests that in this case the thermal diffusion in the helium around the crystal is the bottleneck. The same relaxation behaviour is found when the crystal is heated dielectrically with MW power far off resonance. This supports the assumption that the energy transfer spin-bath is limited by spatial diffusion. If the crystal is surrounded by a He film at a temperature below the λ-point, Շ is found to be the same as in HeII up to a well defined average MW power level. For higher powers the relaxation behaviour is similar to that of CeES immersed in HeI. In Eu²+ ; CaF₂, T₁ is expected to have the form T₁= AT + BT⁵. The observed relaxation time Շ , however, is found to be concentration dependent. All measurements have been done on the +½⇢ -½ transition with H II [100]. For the three lowest concentrations, the temperature dependence of Շ from 1.5 to 4.2°K can be fitted with the expression Շ ¯¹=CT with C = 2.75 (sec°K) ¯¹ for 0.02% Eu, C = 3.5for 0.8% and C = 5 for 0.2%, Շ is shorter and Շ ¯¹ ∾ T ² from 1.5°K to 7°K. The concentrations given correspond to the total Eu content. The Eu²+ concentration has been inferred from the magnitude of the saturation rotation. Շ(T) seems to depend on both Eu²+ and Eu³+ concentrations. It is suggested that exchange coupled pairs of Eu²+ and clusters involving Eu³+ may account for the concentration dependence of Շ. Upper limits of A = 2.5 and B = 5 x 10¯⁵ are found for T₁ by extrapolating the lowest concentrations investigated. These values are somewhat lower than both measured and calculated values found by Huang. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Electron paramagnetic resonance (EPR) signals from tuna ferricytochrome c solutions were obtained between 4.2°K and 77°K, with g-values g(1) = 1.25, g(2) = 2.25, g(3) = 3.05« The g(3) line is 380 gauss wide between 4.2°K and 50°K with Gaussian shape, but has become 700 gauss wide with Lorentzian shape at 77°K. The temperature independent shape and width are best explained by a distribution of rhombic crystal field potentials (r.m.s. deviation = 11%). The Lorentzian shape arises from a short (10(-8) sec.) spin-lattice relaxation time. EPR spectra from horse heart ferricytochrome c single crystals were analysed to obtain the orientation of the g-axes relative to the crystallographic axes. The g(3)-axis was 76° from the crystal c-axis, close to the heme normal (71.5° to c-axis) determined from the 3-dimensional X-ray structure by Dickerson. The other 2 g-axes lay approximately along the N-Fe-N directions in the heme ring. An amended version of Eisenberger and Pershan's theory was used to explain the angular variation of the broad lines (300-2000 gauss) seen in the crystals—best fit was obtained with the distribution of ligand fields from the solution study plus a 1.5° variation in g-axis orientation. The undifferentiated absorption line shapes observed at 4.2°K in both solutions and single crystals were explained by the Portis theory of rapid adiabatic passage in solids. This theory was tested with a model system of charred dextrose, and found to be valid. Using the theory the relaxation time (τ) of the cytochrome c system was found to be, from the phase lag of the EPR signal relative to the magnetic field modulation, 3.8 x 10(-6) sec. at 4.2°K. τ was obtained between 4.2°K and 18°K from the rapid passage signals, and between 50°K and 70°K from the linewidth of the spectra. The temperature dependence of τ below 20°K could arise from a combination of a T(9) Raman spin-lattice relaxation process with a temperature independent spin-spin relaxation time of order 10(-8) seconds (which might arise from dipolar interactions between neighboring iron atoms). / Science, Faculty of / Physics and Astronomy, Department of / Graduate