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The problem of the quadrupole interaction occurring in a vibrating-rotating C₃v symmetric top molecule has been studied in detail. The quadrupole interaction has been treated as another perturbation term to a general frequency expression accounting for the vibrating-rotating interaction of the molecule so that a complete frequency formula is obtained for both interactions, and from which hyperfine spectral components are predicted and measured. The hyperfine transitions in the ground, and v₈=1 and v₈=2 excited vibrational states of the ¹³C isotopes of methyl cyanide have been investigated in the frequency range 17-72 GHz, primarily in the low J transitions (0≤J≤3). The study of the ground state of isotope i3CH3i3CN, and the v₈=1, v₈=2 excited vibrational states for all the isotopes have been conducted here for the first time. A substantial perturbation has been discovered and discussed at the ΔJ=3→4 transitions within the Kl=1 sets in the v₈=1 mode for isotopes ¹³CH₃CN and CH₃¹³CN. A total of 716 hyperfine transitions have been assigned from measurements, only 7 of which have been measured previously. A total of 84 molecular constants have been reported; 70 of these constants are derived for the first time from microwave data.

The identification of energy scales in the region of Isoscalar Giant Quadrupole Resonance (ISGQR) is motivated by their potential use in understanding how an ordered collective motion transforms into a disordered motion of intrinsic single-particle degrees-of-freedom in many-body quantum systems. High energy-resolution measurements of the ISGQR were obtained by proton inelastic scattering at Ep= 200 MeV using the K600 magnetic Spectrometer at iThemba LABS. The nuclei 58Ni, 90Zr, 120Sn and 208Pb, associated with closed shells, were investigated. Both the Fourier transform and Wavelet analysis were used to extract characteristic energy scales and were later compared with the results from the theoretical microscopic Quasi-particle Phonon Model (QPM), including contributions from collective and non-collective states. The scales found in the experimental data were in good agreement with the QPM. This provides a strong argument that the observed energy scales result from the decay of the collective modes into 2p-2h states. The different scale regions were tested directly by reconstruction of measured energy spectra using the Inverse Fourier Transform and the Continuous Wavelet Transform (CWT), together with a comparison to a previously available reconstruction using the Discrete Wavelet Transform (DWT).

Momentos de quadrupólo elétricos de estados isoméricos nucleares com vidas médias entre 10 nanosegundos e 100 milisegundos podem ser medidos com o método Espectroscopia de Mistura de Níveis (Level Mixing Spectroscopy- LEMS), utilizando campos magnéticos variáveis aplicados em núcleos implantados em materiais hospedeiros que possuam gradientes de campo elétrico. O Campo magnético externo pode ser substituido pelo campo hiperfino de materiais ferromagnéticos e sua variação poderia ser controlada variando a temperatura. O objetivo deste trabalho é verificar a viabilidade desta substituição. Implementamos o método LEMS no Laboratório Pelletron usando como caso teste o estado isomérico de 398 KeV do 69Ge que possui todas as suas propriedades nucleares conhecidas (meia vida, spin, momento magnético, momento de quadrupolo elétrico). Ele foi produzido pela reação 56Fe(16O, 2pn)69Ge com o feixe de 16O à 53 MeV (LAB) de energia, e depois implantado em Gadolínio que é ferromagnético abaixo de Tc = 289K. Medimos a anisotropia da radiação gama emitida por esse núcleo em função da temperatura. A comparação entre as medidas da anisotropia em função da temperatura, com medidas da anisotropia em função do campo magnético externo, feita pelo grupo de Leuven/Bélgica, nos levou a duas interpretações possíveis. Na primeira, supondo a interação elétrica constante e independente da temperatura, obtemos um campo magnético hiperfino anômalo para o Gd. Na segunda análise, obtivemos o campo hiperfino variando linearmente com a magnetização, admitindo gradientes de campo elétrico dependentes da temperatura. Medidas futuras usando monocristal de Gd poderão resolver esta ambiguidade, bem como medidas TDPAD (Time Diferencial Perturbed Angular Distribuition) em função da temperatura, na qual se mede diretamente o campo hiperfino. / The Level Mixing Spectroscopy method allows to measure the eletric quadrupole moments of high spin isomeric nuclear states (10ns < t < 100ms) produced in nuclear reactions. The magnetic interaction is usualy created by an intense external magnetic field. The eletric quadrupole interaction can be created by recoi-implantation of the nuclei in non-cub crystals, used as hosts. The external magnetic field can then be replaced by the hiperfine fields of ferromagnetic materials, controling its intensity by temperature variation. The purpose of the research performed for this work is to verify the viability of this replacement. We adapt the LEMS method to be used in the Pelletron Laboratory. We choose the isomeric state at 398 KeV exitation energy in the 69Ge nucleus as a test case, because it has all nuclear properties well known (half-life, spin, magnetic moment, eletric quadrupole moment). It was produced by the 56Fe(16O, 2pn)69Ge reaction, with a 16O beam at 53 MeV, and implanted and stopped in a Gadolinium host, which is a ferromagnet from low temperatures up to Tc=289 K. We measure the anisotropy of the emitted gama ray as a function of the temperature of the host. The comparison of this measurement with another of the anisotropy as a function of an external magnetic field strength, done by the Leuven/Belgium group, show us two possibilities. In the first, we suppose that the eletric interaction is cosntant and independent of temprature and we obtain an anomalous magnetic hyperfine field for Gd. In the second one, we obtain a hyperfine field that follows the magnetization if we assume eletric field gradientes that are temperature dependent. New measurements by using Gd monocrystal and the TDPAD (Time Diferencial Perturbed Angular Distribution) method may solve this ambiguity.

GnRH peptides have been discovered in a wide variety of vertebrate and invertebrate organisms, and work is ongoing to characterize additional unique isoforms. This dissertation describes the investigation of reversed-phase chromatographic and mass spectrometric behavior of GnRH peptides, the development and application of an LC-MS/MS method for qualitative identification of GnRH peptides, and the comprehensive validation of an LC-MS/MS method for simultaneous, quantitative measurement of hydroxyproline9GnRH (Hyp9GnRH) and mammalian GnRH (mGnRH) in rat brain tissues. Chromatographic and mass spectrometric behavior of GnRH isoforms was characterized for six GnRH model peptides. Using reversed-phase high performance liquid chromatography (HPLC), nearly complete separation of the model GnRH peptides was achieved. Evaluation of electrospray source conditions indicated that certain parameters can be adjusted to affect the abundance of selected charge states and improve response. Using the conditions found to be optimal for GnRH peptides in general, a method was developed to facilitate characterization of novel GnRH isoforms or confirm the identity of known isoforms. Fragmentation patterns for six model GnRH isoforms were examined to determine what portion of the primary sequence could be elucidated by de novo sequencing, and a simple solid phase extraction protocol was developed to isolate the model GnRH compounds from tissue samples. Application of the method to rat brain samples resulted in successful isolation and structural confirmation of hydroxyproline9GnRH and mammalian GnRH. A quantitative method for the determination of concentrations of hydroxyproline9GnRH and mammalian GnRH in rat brain tissue was developed and rigorously validated. Guinea pig brains were found to be a suitable substitute matrix for rat brains, and accuracy and precision were determined after four validation runs. Stability of both peptides in samples over long-term storage and under experimental conditions were evaluated, and the LC-MS/MS method was compared to an enzyme-linked immunoassay. Thirty-one brains from Sprague-Dawley rats were analyzed using the LC-MS/MS procedure and compared to published results for Hyp9GnRH and mGnRH.

The aim of this research project was to assemble an apparatus to measure the electric quadrupole moments of gas molecules using the technique of electricfield- gradient-induced birefringence, or the Buckingham effect. Comprehensive research by various workers in the field has shown that this technique provides the only direct means of obtaining the quadrupole moment of a molecule. Theory has shown that the most accurate determination of the electric quadrupole moment is through a study of the temperature dependence of the effect. This not only allows for the quadrupole moment to be obtained but also enables the temperature-independent quadrupole hyperpolarisability term to be extracted. Both the quadrupole moment and the hyperpolarisabilty provide valuable information in a variety of applications, including intermolecular forces, electrostatic potentials and non-linear optical phenomena. This thesis fully describes the apparatus used in these measurements, including a description of the custom built oven that allowed for measurements to be performed over a temperature range spanning from 25"C up to 200"C. Results for the quadrupole moments and quadrupole hyperpolarisabilities of carbon dioxide, carbon monoxide, nitrous oxide and hydrogen are presented, together with a quadrupole moment for carbonyl sulphide from room-temperature measurements. Wherever possible, the results of this work are compared to previously published experimental and theoretical data. / Thesis (PhD) - University of KwaZulu-Natal, Pietermaritzburg, 2009.

Quadrupole ion trap(QIT) mass spectrometry has become one of the most widelyused tools in the analysis of the structure of small molecules. The motion of the ionsstored in the quadrupole ion trap is extremely important. This ion motion within thequadrupole ion trap is controlled by several factors including the m/z ratio and thecollisional cross section of the ion. Investigation of ion motion within the QIT has thepotential to elucidate a new way to separate ions based on these factors. DC tomographyexperiments allow for the trajectory of the ion motion to be measured withoutmodifications to the ion trap. The ability to use DC tomography for separation ofisomeric ions on a commercial GC/MS system was investigated.Investigation of the mass range within the ion trap is necessary for the analysis ofa wide range of molecules. The ability of the quadrupole ion trap to perform MS/MSanalyses can provide insight into the structural information of many compounds.However, there exists a low mass cut-off (LMC) within the quadrupole ion trap and thusinformation about the low m/z fragments from a parent ion is lost. Schwartz and coworkerspresented a new technique labeled pulsed q dissociation (PQD) at the 53rdAnnual ASMS Conference in San Antonio TX in 2005. PQD eliminates the LMC byperforming CID at a qz of 0.4 but, then immediately lowering the q level before the massscan in a linear ion trap. By operating the quadrupole ion trap in this same manner, lowm/z product ions can be detected. This technique and elucidation of the energetic processcontained within PQD were explored further using a modified commercial quadrupoleion trap and the results discussed in this work.

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Thesis (Ph. D.)--University of Washington, 1999. / Vita. Includes bibliographical references (p. 115-123).