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Doctoral Thesis
DOI
10.11606/T.43.2001.tde-04122013-132932
Document
Author
Full name
Max de Oliveira Roos
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2001
Supervisor
Committee
Dias, Helio (President)
Arruda Neto, Joao Dias de Toledo
Chiapparini, Marcelo
Duarte, Sérgio José Barbosa
Pato, Mauricio Porto
Title in Portuguese
Decaimento de ressonâncias gigantes em núcleos esféricos e deformados
Keywords in Portuguese
Física nuclear
Abstract in Portuguese
O decaimento de ressonâncias gigantes (RG's) em núcleos tipicamente esféricos, ANTPOT.40 Ca, ANTPOT.90 Zr e ANTPOT.208 Pb, são interpretados em termos de suas larguras de escape nos processos direto e de pré-equilíbrio. Os cálculos são embasados na Teoria Estatística de Múltiplas Etapas de Núcleo Composto, de Feshbach, Kerman e Koonin (FKK). É feito um estudo comparativo, analítico e numérico, entre as aproximações FKK e de Oblozinsky, no contexto de densidade de níveis, no cálculo das larguras de damping e de escape. No caso das larguras de damping () não há diferença apreciável entre as referidas formulações no intervalo de energia estudado. Por outro lado, para as larguras de escape () podemos ter diferenças apreciáveis dependendo do núcleo, do tipo de núcleon emitido e da própria energia de excitação. A largura total das RG's, (= + ) , para algumas RG' s nos núcleos mencionados acima, é comparada com dados experi-mentais e com outros cálculos teóricos, obtendo-se uma razoável concordância de resultados. No que se refere a núcleos deformados, apresentamos uma proposta teórica para o cálculo da largura de escape do decaimento direto de RG' s. Consideramos um núcleo constituído de um coroço levemente deformado com simetria axial acoplado a um par partícula-buraco. O sistema formado decai, emitindo um núcleon, através do processo direto.
Title in English
Decay of giant resonances in spherical and deformed nuclei
Keywords in English
Nuclear physics
Abstract in English
The decay of Giant Resonances (GR's) in typically spherical nuclei, 40Ca, 90Zr e 208Pb, are interpreted in terms of its escape widths in the direct and preequilibrium processes. The calculations are based in the Statistical MultiStep Compound theory of Feshbach, Kerman anel Koonin (FKK). It is made a comparative study, analytical and numeric, between the FKK and oI Oblozinsky approaches, in the level density context, for the calculations of the damping and escape widths. In the case of the damping widths () there is no appreciable difference among the mentioned formulations in the energy interval studied. On the other hand, for the escape widths () we can have significant differences depending on the nucleus, of the type of emitted nucleon and of the excitation energy. The total wiedth (= + ), for some GR´s of the nuclei mentioned above, it is compared with experimental data and with other theoretical calculations, being obtained a reasonable agreement among the results. For deformed nuclei, we presented a theorctical proposal for the calculation of the escape width in the direet decay of a given GR. We considered a nucleus constituted of a core softly deformed with axial symmetry coupled to a pair particle-hole. The formed system decay emitting a nucleon through direct process
 
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PSRE33633Roos.pdf (2.51 Mbytes)
Publishing Date
2014-02-21
 
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