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The nuclear magnetic resonance spectrum of the protons in the water of hydration in a single crystal of natrolite has been investigated and analysed according to Pake’s theory in order to locate the protons in the structure. The line shape of the proton resonance in natrolite powder was studied over a wide range of temperature. The observed changes in the line shape partially revealed the dynamics of the water of hydration. / Thesis / Master of Science (MSc)

A direct method for measuring the resonance escape probability, p, in thorium-water lattices was experimentally examined. The system under investigation consisted of a square, close-packed, lattice of hollow aluminum clad thorium metal slugs (1.207 inch O.D., 0.495 inch I.D.) in. water, spaced to give a water to thorium ratio of 2 to 1 by volume (water to metal 1.45 to 1). A substitute lattice, in which the thorium was repla~ed by lead, was also used to give the same scattering properties as thorium but no resonance capture. The neutron source consisted of a fission plate made of a disc of U-235 (0.900 inch in diameter, 5 mgs in weight) mounted at the end of a Cd-covered aluminum tube which conducted a beam of neutrons from inside the thermal column of the VPI reactor into the lattice. Cd-covered indium foils were used to measure. flux traverses in two perpendicular directions, parallel to the slugs (denoted by II ) and perpendicular to the slugs (denoted by ⊥ ). 2 The curves of Ar² vs r, where A is the normalized relative activation of the foils, corrected for activation by epithermal neutrons from the primary source (reactor), were integrated to infinity and the ratio of the integrals in the thorium and lead lattices yielded p. It was found that p_⊥ and p₁₁ differed by only one percent, which was within the experimental error. It was therefore concluded that there was no anisotropy in the resonance absorption and the average of the two values, 0.88 ± 0.015, was taken as the value of p for the lattice. The experiment yielded also the age 𝛕 to indium resonance energy: In thorium lattice, 𝛕_⊥ = 44 ± 2 cm², 𝛕₁₁ = 46 ± 2 cm² In lead lattice, 𝛕_⊥ = 47 ± 2 cm², 𝛕₁₁ = 49 ± 2 cm² / Ph. D.

Over the past ten to fifteen years the area of Nuclear Magnetic Resonance (NMR) Spectroscopy has seen tremendous growth. For example, in conjunction with multiple quantum NMR, molecular structural mapping of a compound can be easily performed in a two dimensional (2D) experiment. However, only two kinds of detector coils have been typically used in NMR studies. These are the solenoid coil and the Helmholtz coil. The solenoid coil was very popular with the permanent and electromagnet NMR instruments. With the advent of the superconducting magnets the popularity shifted to the Helmholtz coil, which remains the most common coil today for superconducting magnets. The Helmholtz coil, however, has been shown to have lower sensitivity than the solenoid coil. Hoult (1) has pointed out that potentially the Helmholtz coil represents a loss of signal-to-noise (S/N) by a factor of three in comparison to the solenoid coil. Since Hoult's original work, alternate methods for optimizing S/N have been explored. One of these has been the suggestion of toroid shaped resonators for NMR studies (2). A potential advantage of a toroid cell and coil is the confinement of the B₁ field to the torus region.It has been suggested that the toroid has a potential (S/N) advantage of 3.9 - 4.5 in comparison to the conventional Helmholtz cell (3). Since Zero Quantum (ZQ) experiments are independent of B₀ homogeneity, 2D ZQ experiments provide a convenient method of comparing the toroid and Helmholtz coils. In these zero quantum studies, the toroid and Helmholtz probes will be characterized in terms of several factors 1) B1 homogeneity, 2) B₀ homogeneity, 3) flip angle dependence, and 4) sensitivity. Finally, the two probes will be contrasted using spectral analysis in the spin-spin mapping of a simple molecule (nâ butanol) and a complex molecular system (taxol). / Master of Science

Indirect nuclear spin-spin coupling constants in high resolution nuclear magnetic resonance (NMR) spectroscopy provide the most powerful method for determining conformations and structures of molecules in solution. The research described in this dissertation establishes the conformational and substituent dependencies of several new types of nuclear spin-spin coupling for use in structural studies. It was also of interest to determine the electronic factors which lead to the observed experimental trends. Geminal, vicinal, and four-bond carbon-carbon nuclear magnetic resonance coupling constants were studied experimentally with fifty carbon-13 enriched alicyclic compounds. Because of the small magnitudes of many of these coupling constants it ~vas necessary to modify existing Fourier transform NMR equipment to perform J-resolved two-dimensional NMR experiments. With the greater spectral resolution it was possible to determine 56 intercarbon geminal (²J(cc)), 107 vicinal (³J(cc)) and 26 four-bond (⁴J(cc)) coupling constants. These data represent the largest collection of ²J(cc), the only known data for ⁴J(cc), and the most accurate compilation of vicinal ¹³C-¹³C coupling constants. In combination with molecular orbital methods, the relevant conformational and substituent trends in each of these series were elucidated. Because of the great amount of interest in the importance of bridgehead interactions in "strained" molecules, a study is presented of coupling transmitted via nonbonded interactions between the bridgehead carbons in a series of l-substituted-bicycloalkanes. The two-dimensional Fourier transform methods were again used to obtain the experimental coupling constants and molecular orbital methods were used to determine the importance of the intercarbon bridgehead interactions on ¹H-¹H, ¹³c-¹H, ¹³C-¹³C, ¹³c-¹⁹F , and ¹H-¹⁹F coupling constants. In all cases the nonbonded interactions increased dramatically as the separation between the bridgehead carbons decreased. Further understanding of mechanisms of "through space" coupling were based on NMP. studies of the long range coupling constants (⁵J(HF) and ⁴J(HF)) in N-methyl-8-fluoroquinolinium halides. The X-ray structure of N-methyl-8-fluoroquinolinium chloride was determined in an attempt to calculate the observed ⁵J(HF) and ⁴J(HF). A selective population inversion mIR method was used to show that the sign of ⁵J(HF) in N-ethyl-8- fluoroquinolinium iodide is positive.

Raman vibrational bands are sensitive to fluctuations in the molecular environment. Variations in the bandwidth and peak position can then be utilized to monitor molecular forces and interactions present in condense phases. Nuclear Magnetic Resonance (NMR) provides a convenient probe for the study of molecular reorientation in liquids since nuclear spin relaxation times are dependent on the details of molecular motion. Presented here is the solvent study of the Raman bandwidths and frequency displacements of the mode of the compounds CH3MCI3 (M = C, Si, Ge, Sn) in a number of solvents of widely varying molecular structure. Also, a detailed isotope dilution study of the modes in CH2CI2/CD2CI2 mixtures is presented. In this set of experiments, I observed broadening of the v1 mode of CH2C12 upon dilution,which is the first experimental observation of such behavior. The temperature-dependent carbon-13 relaxation times and nuclear Overhauser enhancements in neat dichloromethane were measured. In this study we found that the molecular reorientation of this molecule was highly anisotropic, but could be well characterized assuming quasi-symmetric top behavior. In addition, in order to gain a more complete understanding of the reorientational dynamics in dichloromethane, we analyzed the 13-C NMR relaxation of CH2CI2 both in "inert" solvents of differing viscosities and in interactive solvents of varying Lewis basicities. Various theoretical models were also applied in order to characterize dichloromethane1s reorientational dynamics.

This work examines the use of higher order multiphoton resonances in higher harmonic generation together with judicious exploitation of coherent interaction properties to achieve efficient harmonic generation. A detailed experimental study on third harmonic generation in two photon resonant coherent interaction and a theoretical study on four photon resonant coherent interaction have been conducted. Two photon resonant coheren propagation in lithium vapor (2S-4S and 2S-3D interaction) has been studied in detail as a function of phase and delay of the interacting pulse sequence. Under coherent lossless propagation of 90 phase shifted pulse pair, third harmonic generation is enhanced. A maximum energy conversion efficiency of 1% was measured experimentally. This experiment shows that phase correlated pulse sequence can be used to control multiphoton coherent resonant effects. A larger two photon resonant enhancement does not result in more efficient harmonic generation, in agreement with the theoretical prediction. An accurate (to at least 0.5 A°) measurement of intensity dependent Stark shift has been done with the newly developed "interferometric wavemeter." Stark shifts as big as several pulse bandwidths (of picosecond pulses) result in a poor tuning of multiphoton resonance and become a limiting factor of resonant harmonic generation. A complete theory has been developed for harmonic generation in a four photon resonant coherent interaction. A numerical application of the theory to the Hg atom successfully interprets the experimental observations in terms of the phase dependent stimulated Raman scattering. With the intensity required for four photon resonant transition, the calculation predicts a dramatic Stark shift effect which completely destroys the resonance condition. This model provides a basis for the development of future schemes for efficient higher order coherent upconversion.

Analysis in chemistry has always been hindered by the presence of impurities in samples or mixtures that are difficult to separate. Nuclear magnetic resonance has proven to be one of the most powerful analysis techniques to enable the study of mixtures by pseudoseparation using molecular parameters such as the diffusion coefficient through the application of the DOSY technique. In order to extend the application of this technique, an improvement has been proposed know as matrix-assisted DOSY (MAD-DOSY) or chromatographic NMR. This technique is based on the addition of a sample modifier that will interact differently with the molecules, varying and separating their diffusion coefficients, or even changing slightly the chemical shifts. To extend the application of chromatographic NMR, size exclusion stationary phases have been combined with DOSY experiments. These studies have been applied to analyze mixtures modifying the diffusion coefficient in terms of size exclusion behavior and to increase the understanding of the interactions between the analytes and the stationary phase. These studies have been published in Magnetic Resonance in Chemistry. One of the main issues when using DOSY is spectral overlapping, which is the main cause of poor resolution. In addition to this problem, a consequence of using stationary phases is the appearance of increased broadening of the signals due to differences in magnetic susceptibility. Thus, to achieve the aim, the study of diffusion properties have been performed under HR-MAS conditions which can help to remove susceptibility effect, but has complicating effects on the DOSY experiment. A method to obtain reliable diffusion measurements under HR-MAS have been developed using a D2O sample. Different conditions have been investigated including different pulse sequences, variation of parameters of the pulse sequence (diffusion delay or gradient strength), spinning rate and synchronization of the pulse sequence with the sample spinning. Also improvements in sample preparation as the addition of spacers in different locations of the sample rotor, to both reduce radial field variations and the sample volume, in order to obtain the most accurate diffusion values. This method have been published in Magnetic Resonance in Chemistry. The method have been applied to a wide range of molecules to extend the understanding of diffusion under HR-MAS conditions. In order to extend the range of application of NMR chromatography, a complementary study of the analysis of a mixture of different enantiomers including ethylenediamine cobalt complexes, aminoacids and some other organic small molecules adding to the sample a chiral stationary phase as a sample modifier is included in the final chapter of this thesis.

Nuclear magnetic resonance force microscopy (NMRFM) of a micron size sample of ammonium sulfate was performed by measuring the cantilever deflection produced by coupling the magnetic force to a mechanical cantilever at its resonance frequency. Spin-lattice and spin-spin relaxation measurements were obtained with our newly developed NMRFM probe. A system with more advanced positioning, acquisition and analysis has been fabricated. A new device in which a semi-automatic system performs nanoposition control, spin manipulation, dynamical measurements, and data analysis has been demonstrated to be successful. The new system has proven to be an improvement with respect to other versions of NMRFM probes, thanks to its versatility for pulse sequence designs, faster data acquisition, and automatic analysis of the information. This thesis presents an explanation of the theoretical details of nuclear magnetic resonance force microscopy, and experiments are described in which dynamical measurements of proton spin interactions are obtained. Finally, relaxation time e ffects of the observed force signal are considered in detail. A novel spin manipulation technique which is being implemented for future measurements is described in detail, and magnet con figurations for larger magnetic field gradients and consequently larger signal-to-noise ratio, are also described. / text

Thesis (Ph. D.)--Florida State University, 2005. / Advisor: Dr. John R. Quine, Florida State University, College of Arts and Sciences, Dept. of Mathematics. Title and description from dissertation home page (viewed Sept. 19, 2005). Document formatted into pages; contains x, 69 pages. Includes bibliographical references.