The level structures of ('94)Ru, ('90)Mo, ('88)Zr, ('89)Mo and ('89)Nb have been studied via the decay of two isomers of ('94)Rh, two of ('90)Tc, two of ('88)Nb, one of ('89)Tc and one of ('89)Mo, respectively. These nuclides were produced via the proton bombardment of isotopically-enriched ('96)Ru and ('92)Mo as well as naturally-occurring Zr. Using gamma and beta spectroscopy techniques, detailed level schemes have been produced. / High-spin states in ('89)Nb, ('88)Zr and ('88)Nb have been studied with in-beam gamma-ray spectroscopy techniques. These nuclides were produced with alpha particle-induced reactions on ('89)Y. A neutron-multiplicity experiment was used to identify the nucleus to which several gamma-rays belong. / The systematics of the N = 48 and 47 nuclei, along with theoretical descriptions based on the nuclear shell model, are discussed. Contributions to original knowledge are summarized in Chapter V.

Low Temperature Nuclear Orientation (LTNO) is an important technique in the study of nuclei far from stability. The theory of LTNO and its applications to the measurement of static nuclear moments and other quantities of spectroscopic interest are reviewed. Among the nuclei off the line of stability those in the A ~ 75 region are of considerable interest, exhibiting large quadrupole deformations, triaxiality and shape coexistence. LTNO measurements performed on neutron deficient bromine isotopes have yielded the static magnetic dipole moments of the nuclei <sup>72g,72m,74m,75,76,77<sup>Br, Spectroscopic information on ^72-77Se and also identified the ground state spin of ⁷³Br as l/2‾ Existing odd A and odd-odd particle-rotor computer codes have been extended in order to include a Variable Moment of Inertia (VMI) asymmetric rotational core. The formalism necessary for this modification is developed. The measured magnetic moments are interpreted within the framework of this particle - VMI rotor model. It is shown that the systematic reduction in the moments of the odd A nuclei ^75-81Br characterizes the transformation of the prolate ground state configuration from largely π[301]3/2 in ^79,81Br to almost pure π[312]3/2 in ^75,77Br. This trend is fully consistent with the increase in deformation towards the lower masses suggested by the known electric quadrupole moments. In contrast, the ground state spin of ⁷³Br can only be interpreted in terms of an oblate nuclear shape. This is the first evidence for the predicted prolate-oblate shape transition in the bromine nuclei. In addition the magnetic moment of ⁷⁴Br^m, by identifying a π[431]3/2ν[422]5/2 configuration, strongly suggests a positive parity assignment for the isomeric state. Finally, an experiment to search for possible T-violation effects in nuclear gamma decay is described. Using coincidence techniques, a measurement of the T-odd P-even quantity (I ‧ k x e)(I ‧ k)(I ‧ e) has lead to a limit on the T-violating phase angle between the E2 and Ml matrix elements associated with the 604 keV gamma transition in ¹⁹²Pt of sin η = ±11(12) x 10^-3.

The inelastic scattering reaction ¹⁶0+¹²C has been studied in the centre-of-mass energy region from 37.7 MeV to 51.4 MeV, in a search for evidence for a seven-alpha chain state in ²⁸Si. The decay products were detected in coincidence at angular separations around 90° in the centre of mass using two position-sensitive strip detectors. Kinematic reconstruction of the quasi-three body final states yielded the differential cross-sections for the decay channels leading to excited states in ¹²C, ¹⁶0 and ²⁰Ne. The excitation functions measured for the <sup>12 C(0+₂)-¹²C(0+₂)-U+03B1 and 12^C(0₂)-⁸Be-⁸Be final states agree broadly between the three experiments that were performed, but contain no structure. Reaction channels have also been identified leading to the ⁸Be-²⁰Ne* and ¹²C*-<sup>16<sup>0* final states. The cross-sections for the ⁸Be-²⁰Ne* decay channels, with the ²⁰ Ne in its lowest excited states, have been compared with previous measurements and provide good agreement. However, none of the excitation functions for these channels contain any structure. The absence of structure in any of the final states, that were identified in this study, indicates that a ²⁸Si chain state is probably not being observed. The same model, that predicts that the seven-alpha chain state should lie in this excitation region in ²⁸Si, has also been used to assign a six alpha chain structure to a resonance at E_x=46.6 MeV in ²⁴ Mg. These two results are compared, and possible reasons for the absence of evidence for a ²⁸Si chain structure are discussed.

<p>The odd &ndash / odd Tl nuclei with A &ge / 190 have moderate oblate nuclear deformation and show rotational bands built on different quasiparticle excitations. Several phenomena, not yet fully understood, were observed in these nuclei, such as large signature splitting in the yrast band (built on a &pi / h9/2&otimes / &nu / i13/2 configuration), possible non &ndash / axiality of the nuclear shape, etc. In this work the high &ndash / spin states in 194Tl were studied. The 194Tl nuclei were produced in the 181Ta (18O, 5n) 194Tl reaction at a beam energy of 93 MeV and the &gamma / - rays were detected using the AFRODITE array. The obtained extended level scheme of 194Tl is presented and discussed in this work. CSM (Cranking shell model) and TRS (Total Routhians Surface) models were both applied to interpret the results for band 1. The results were compared with the neighboring isotone 193Hg.</p>

Thesis (Ph.D.) -- McMaster University, 1998. / Includes bibliographical references (leaves 83-94). Also available via World Wide Web.

Thesis (Ph.D.) -- McMaster University, 1998. / Includes bibliographical references (leaves 241-264). Also available via World Wide Web.

Thesis (Ph. D.)--University of Chicago, Dept. of Physics. / Includes bibliographical references. Also available on the Internet.

Este trabalho apresenta o procedimento que desenvolvemos e empregamos para determinar os valores a serem adotados para as energias de um conjunto de raios gama comumente utilizados como padrões de calibração, bem como sua respectiva matriz de covariância, esta obtida pela primeira vez. A matriz de covariância entre as energias destes padrões revelou muitos casos de correlações com valores absolutos maiores que 0,8, correlações estas que precisam ser corretamente consideradas para não comprometer a qualidade das análises efetuadas com o uso daquelas energias. No procedimento desenvolvido foi considerada a relação entre as energias dos raios gama (em múltiplos de eV) e as constantes fundamentais das quais dependem: h, e, c e o parâmetro de rede do Silício (aSi), o que possibilitou atualizar os resultados para as constantes fundamentais recomendadas de 2002. Uma metodologia para a inclusão de novos resultados experimentais ao conjunto de padrões de modo a preservar sua auto-consistência também foi desenvolvida neste trabalho. Este método considera adequadamente as covariâncias e atualiza todo o conjunto de padrões para incorporar as novas informações experimentais em uma única etapa. Por fim, utilizamos as metodologias de análise desenvolvidas e o conjunto de padrões aqui recomendados para analisar dados de medidas dos raios gama do decaimento do 233U e, assim, estudar a adequação de três diferentes modelos de estrutura nuclear para o 229Th, bem como as energias de excitação dos estados nucleares. A energia do primeiro estado excitado do 229Th, um estado metaestável de energia inferior a 10 eV, foi determinada com base naqueles diferentes modelos. / This work presents the procedure which we have developed and employed to determine the values to be adopted for the energies of a set of gamma-rays in common use as calibration standards, publishing for the fist time their respective covariance matrix. Several correlations with absolute values exceeding 0.8 were found, revealing the necessity of considering correctly the covariance matrix in any analysis to be done with the use of these standards in order not to interfere with the quality of the analysis. The procedure here presented considers correctly the relation between the gamma-ray energies (given in eV) and the fundamental constants h, e, c, and the lattice parameter (aSi), allowing the updating of the set with respect to the 2002 recommended values for those constants. A methodology for the inclusion of new experimental results in the set of standards, in a way which preserve its selfconsistency, was also developed in this work. In this method the updating of the whole set of standards is performed in a single step, while considering adequately the covariances. Finally, the standard set recommended here and the methodology developed in this work were employed to analyze data of gamma-rays measurement which follow the 233U decay and therewith to decide about the adequacy of three different nuclear structure models for 229Th and the excitation energy of its nuclear states. The energy of the first excited state of 229Th, a meta-stable state of less than 10 eV, was determined taking into account those different models.

Parâmetros de deformação nuclear de massa, inéditos, e de carga, associados aos primeiros estados 2 POT.+ dos isótopos ANTPOT.100 Ru, ANTPOT.102 Ru e ANTPOT.104 Ru, foram extraídos simultaneamente a partir da análise de espalhamentos inelásticos de dêuterons e partículas alfa. Foram obtidas distribuições angulares, com dêuterons incidentes de 13,2 MeV, detalhando a região de máxima interferência nuclear-coulombiana, utilizando-se emulsões nucleares no plano focal de um espectrógrafo magnético tipo Enge. As medidas de espalhamento elástico e inelástico de partículas alfa forma realizadas, com a utilização de detetores de barreira de superfície, compreendendo funções de excitação, em = 172,8 POT. 0, entre 9 MeV e 17 MeV (incluindo regiões de excitação coulombiana pura e de interferência nuclear-coulombiana), e também distribuições angulares a 22 MeV para o ANTPOT.100 Ru. Ajustes das distribuições angulares e funções de excitação dos espalhamentos inelásticos, com previsões DWBA calculadas com fator de forma coletivo, permitiram a extração dos parâmetros de deformação, através de metodologia criticamente estabelecida no presente trabalho. A informação original de estrutura nuclear obtida refere-se a um aumento da deformação nuclear de massa com acréscimo do número de nêutrons, que entretanto, definitivamente não acompanha o aumento da deformação de carga. A coerência entre os resultados com os dois projéteis e a ótima concordância com os dados de excitação coulombiana da literatura convalidam o método de medida e de análise. / Nuclear deformation parameters characterizing separately the mass and the charge contributions to the excitation of the first 2 POT.+ states of ANTPOT.100 Ru, ANTPOT.102 Ru and ANTPOT.104 Ru were simultaneously extracted in the analysis of inelastic scattering of both deuterons and alpha-particles. Angular distributions detailing the region of maximal coulomb-nuclear interference were recorded for deuterons of 13.2 MeV incident energy, with nuclear emulsions at the focal plane of an Enge split-pole magnetic spectrograph. Elastic and inelastic alpha-particle scattering was observed with surface barrier detectors, both as excitation functions at = 172,8 POT. 0, for alpha energies between 9 MeV and 17 MeV (covering pure coulomb excitation and interference), and as an angular distribution for ANTPOT.100 Ru at 22 MeV. The deformation parameters were extracted by means of DWBA fits to these data, employing a collective form factor within an analysis method critically established in the present work. The original nuclear structure information thus obtained gives evidence for an increase of the nuclear mass deformation as one or two neutrons pairs are added, but in a definitely less pronounced way than that of the charge deformation. The very good agreement between our results obtained with both deuterons and alphas, and with coulomb excitation experiments, validates the method of measurement and analysis.

Neste trabalho estudamos a dependência do calibre nos cálculos modelo do fator de forma transverso elétrico para núcleos complexos. Foram consideradas as diferentes prescrições que procuram levar parcialmente em consideração os efeitos da corrente de dois corpos, no cálculo do fator de forma transverso elétrico, através dos vínculos impostos pela equação da continuidade. Quando os estados nucleares satisfazem a equação de Schrödinger e a corrente a equação da continuidade as prescrições coincidem. Entretanto, em geral, essas condições não são satisfeitas, surgindo assim as diferenças entre elas, que pode ser interpretada como uma dependência do calibre no cálculo do fator de forma transverso elétrico, Nosso objetivo neste trabalho é mostrar a importância, em núcleos complexos) da dependência do calibre oriunda da violação da equação de Schrödinger pelas funções de onda modelo. Nós fazemos uma análise para verificar sua origem e, para demonstrar sua importância quantitativa, comparamos cálculos do fator de forma na TDA e na RPA, para estados coletivos de paridade negativa no 16 ANTPOT O e 40 ANTPOT Ca. Esta comparação mostra uma considerável diminuição da dependência do calibre quando passamos da TDA para RPA. / In this work we study the gauge dependence of mode) calculations of transverse electric form factors in complex nuclei. We consider the different prescriptions that try to take partially into account the effects of the two-body current, in the calculation of the transverse electric form factor, through the continuity equation constraints. When the nuclear states obey the Schrodinger equation and the current density the continuity equation, the prescriptions coincide. However, in general, these two conditions are not satisfied and therefore they differ which can be seen as a gauge dependence in the calculation of the transverse electric form factor. Our aim is to show the importance in complex nuclei, of the gauge dependence that comes from the violation of the Schrödinger equation by the model wave functions. We perform an analysis to identify its origin and, to give evidences of its quantitative importance, we compare TDA and RPA calculations of transverse electric form factors for collective states of negative parity in 160 and 46Ca. This comparison shows that the gauge dependence diminishes considerably in RPA.