Thesis (M. Phil.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves [86]-88).

Thesis (Ph. D.)--University of Queensland, 2002. / Includes bibliographical references.

published_or_final_version / Physics / Master / Master of Philosophy

Quantitative multielemental analysis using Particle Induced X-ray Emission (PIXE) using 1 and 2 MeV proton bombardment on thin targets has been achieved. The method is based on the calculation of atomic ratios from experimentally determined relative x-ray efficiency curves. Sample preparation techniques involving digestion and homogenous deposition of samples and standards with a minimum of contamination have been investigated. The accuracy of the method has been evaluated using five standard reference materials obtained from the National Bureau of Standards. The elimination of bremsstrahlung associated with the charging effect of non-conducting samples in PIXE analysis has been accomplished using thin carbon foils in the beam path. Applications of the PIXE technique to studies on deep-sea ferromanganese nodules were performed. The utility of PIXE in the analysis of noduoles and in the following of the distribution of a large number of elements through the various stages of a processing scheme were demonstrated.

No description available.

<p>Gamma ray spectroscopy has provided enormous amounts of information on the behaviour and structure of atomic nuclei [SHA88, BEA92, EBE08]. Most of the major discoveries in experimental nuclear physics over the last five decades are strongly associated with improvements in detector technologies. Inorganic scintilators led to the discovery in 1963 of the first excited states of a rotational band based on the ground state of 162Dy. Improvements in peak-to-background ratios and detector resolutions obtained with germanium led to the first evidence of backbending which is associated with a two quasi-particle excitation in 162Dy [SHA88]. More recently the development of composite and highly-segmented Ge detectors has significantly increased the performance and power of detection systems. The Clover detector is such a detector system and is in use at iThemba LABS. This study concerns the evaluation of the particle transport code MCNPX 2.5.0 as a tool to model complex composite detectors such as the Clover. Lanthanum silicate (LSO) and Lead tungstate (PbWO) are also evaluated as possible suppressor shield materials. It is shown that reasonable agreement between experiment and simulation is found when the experiment is accurately reproduced. However, when complex detection modes are implemented in the detector based on the number of elements that fire, MCNPX cannot be used to model the detector performance exactly. Differences between simulated and experimental results are found in suppressed add-back mode. It is proposed that the discrepancies are due to limitations in implementation of the pulse-height and special anti-coincidence tally in MCNPX. LSO and PbWO are compared to BGO as suppressor shield materials. It is found that LSO is not an ideal material for a suppression shield. PbWO is shown to give performance values similar to that of BGO. The back-plug is shown to have no effect on the Peak-to-Total ratio but is effective at reducing the background at lower energies.</p>

The phosphine(III) crown ethers, [4'-(N-phenylaza-15crown-5)]3P (1), [4'-(N-phenylaza-l8-crown-6)]3P (2), [4'-(Naza-18-crown-6)]2-Ph-P (3), and [4'-(benzo-15-crown-5)]3P (4) were synthesized by using an electrophilic bromination of the crown phenyl ring (with a tribromide ion) followed by the preparation of a lithium salt and subsequent reaction of the resulting lithiocrowns with P(III) reagents. The oxide of compound 1 was completely characterized by an X-ray diffraction study, which showed that structurally there is not a significant difference in P-O bond distances and OPC bond angles with [4'-(N-phenylaza-15-crown-5)]-Ph2-P=O. Thespectroscopic data of compound 1 and 2 were compared. It appears that 1 and 2 are similar in P environment; also they are more air sensitive than 3 and 4. In addition, a discussion about compounds 1-4, and a literature review of the preparation of phosphines are included. / Department of Chemistry

High spin states in ⁸⁰Sr have been studied using the techniques of in-beam γ-ray spectroscopy. The reaction used was ⁵⁴Fe(²⁹Si, 2pn)⁸⁰Sr at beam energies between 85 and 110 MeV. γ-γ coincidence measurements were performed with a thin target to investigate the level structure. Both neutron gated and singles angular distribution measurements were carried out to aid in the assignment of level spins. The directional correlation ratios extracted from the γ-γ coincidence data provided a consistency check for the spin assignments. Level lifetimes were measured by the Doppler shift attenuation method in a thick target γ-γ coincidence measurement. The ground state band has been identified up to (26⁺) and three previously unobserved sidebands have been discovered. The deduced level scheme is compared with cranking model calculations; the predicted transformation to mostly non-collective excitations of an oblate shape is not observed experimentally. The behaviour of the J⁽¹⁾ and J⁽²⁾ moments of inertia is discussed and presented as evidence for either static or dynamic γ-deformation in the light Sr isotopes. In addition, the level structure is compared with IBM-2 calculations. These calculations indicate the importance of proton excitations across the Z=40 subshell gap, into the g_9/2 orbital, and suggest that the lowest lying ⁸⁰Sr sideband can be identified with the collective IBM-2 quasi-γ band. NUCLEAR REACTIONS ⁵⁴Fe(²⁹Si, 2pn), ,em>E = 85 - 110 MeV; measured Eγ, Iγ(θ), γ-γ, n-γ coincidences, DCO ratios, Doppler shifted γ-ray lineshapes. ⁸⁰Sr deduced levels, J, π, τ. Enriched target, Ge(Li), Ge, NE213 detectors.

No description available.

Typescript. / Thesis (Ph. D.)--University of Hawaii, 1970. / Bibliography: leaves [76]-79. / vi, 79 l maps, graphs, tables