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Doctoral Thesis
DOI
10.11606/T.43.2010.tde-21102010-110812
Document
Author
Full name
Maria Carmen Morais
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2010
Supervisor
Committee
Lichtenthaler Filho, Rubens (President)
Arazi, Andrés
Carlson, Brett Vern
Chamon, Luiz Carlos
Lewin, Thereza Borello
Title in Portuguese
O efeito de estados de estrutura alfa no espalhamento 16O+12C e na reação de captura astrofísica 12C()16O
Keywords in Portuguese
Estrutura alfa
Fator S
Transferência elástica
Trnasferência inelástica
Abstract in Portuguese
Neste trabalho, investigou-se o espalhamento elástico 16O+12C, considerando o efeito da troca de uma partícula alfa entre o projétil e o alvo que conduz aos mesmos núcleos do canal de entrada (transferência elástica). Foram analisadas distribuições angulares em uma faixa de energias que, no referencial de centro de massa, vai de 8,55 MeV até 56,57 MeV. A barreira coulombiana desse sistema está em torno de 11MeV. Foram realizadas medidas de distribuição angular das reações de transferência elástica e inelástica no sistema 16O+12C, em Elab = 46, 26 MeV. A análise dessas medidas forneceu os fatores espectroscópicos, 12C+_alfa _ 16O, do estado fundamental e dos estados excitados J_ = 2+ e J_ = 1, ambos logo abaixo do limiar de emissão alfa, em 7,16 MeV. A partir do valor da amplitude espectroscópica do estado J_ = 2+, determinou-se um valor confiável para o Coeficiente de Normalização Assintótica, 1,05± 0,13(105 fm1/2), este valor foi usado para calcular a largura reduzida desse estado e realizando um cálculo de matriz R determinou-se o fator S astrofísico em energias em torno do pico de Gamow, S(E2)=37keVb.
Title in English
Effect of alfa states in the 16O+12C scattering and in the 12C+alfa, 8)16O capture reaction of astrophysical interest
Keywords in English
Alpha structure S factor
Elastic transfer inelastic transfer
Abstract in English
The 16O+12C elastic scattering was investigated considering the effect of exchange of an alpha particle between projectile and target leading to the same nuclei of the entrance channel (elastic transfer). Angular distributions were analyzed in an energy range from 8.55 MeV to 56.57 MeV in the center of mass frame. The Coulomb barrier is around 11MeV for this system. Measurements of angular distributions of elastic and inelastic transfer reactions to states of the 16O in the 16O+12C system were performed at Elab = 46, 26MeV. Those measurements provided the spectroscopic factors of 12C+_ 16O for the ground state and for J_ = 2+ and J_ = 1 16O excited states, both just below the _-threshold at 7.16 MeV. The Asymptotic Normalization Coefficient (ANC) for the J_ = 2+ state was obtained (1.05 ±0,13(105 fm1/2)) and used to calculate the reduced width of this state, with this value a R-matrix calculation was performed to determine the astrophysical S-factor in energies around the Gamow peak, S(E2)=37keVb.
 
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tese_MariaCarmen.pdf (3.27 Mbytes)
Publishing Date
2010-12-20
 
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