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Doctoral Thesis
Full name
Wagner Sciani
Knowledge Area
Date of Defense
São Paulo, 1996
Lepine, Alinka (President)
Galetti, Diógenes
Gomes, Paulo Roberto Silveira
Herdade, Silvio Bruni
Pereira, Dirceu
Title in Portuguese
Estudo do potencial de interação entre 12C e 24Mg: um exemplo de transparência anômala
Keywords in Portuguese
Barreira Coulombiana
Canais acoplados
Espalhamento elástico
Reações nucleares
Relação de dispersão
Abstract in Portuguese
Foram medidas distribuições angulares completas do espalhamento elástico do sistema 'ANTPOT. 12 C' + 'ANTPOT. 24 MG' nas energias 'E IND. CM' = 10.67 e 11.33 MeV e entre 'E IND. CM' = 12.0 e 16.0 MeV, usando feixe de 'ANTPOT. 12 C' produzido no acelerador Pelletron. Esta faixa de energia se localiza parcialmente abaixo e em torno da barreira coulombiana, estando a barreira em 12.53 MeV. Surpreendentemente todas as distribuições angulares apresentam fortes oscilações mesmo aquelas em energias abaixo da barreira coulombiana. As distribuições angulares foram ajustadas com cálculos de modelo óptico, sendo possível determinar o potencial mais raso, sem ambigüidades contínuas. As principais características deste potencial são: potencial extremamente transparente inclusive no interior nuclear e forte dependência com a energia nas profundidades real e imaginária 'V IND. 0' e 'W IND. 0'. Em cinco energias também foram analisadas distribuições angulares do espalhamento inelástico e ajustadas por cálculos de canais acoplados. Os potenciais ópticos usados para diferentes canais apresentam a anomalia do limiar e cálculos de relação de dispersão conectando as integrais de volume dos potenciais ópticos reproduzem bem esta anomalia.
Title in English
Study of the interaction potential between 12C and 24Mg: an example of anomalous transparency
Keywords in English
Coulomb barrier
Coupled channels
Dispersion relation
Elastic scattering
Nuclear reactions
Abstract in English
Complete angular distributions of the elastic scattering 'ANTPOT. 12 C' + 'ANTPOT. 24 MG' were measured at 'E IND. CM' = 10.67 and 11.33 MeV and from 'E IND. CM' = 12.0 to 16.0 MeV, using a 'ANTPOT. 12 C' beam produced at Pelletron Accelerator. This range of energy is close to the Coulomb barrier of the system, which is 12.53 MeV. Surprisingly all the angular distributions show strong oscillations even at energies bellow the Coulomb barrier. The angular distributions were fitted by optical model calculations and we determined the shallowest real potential, without continuos ambiguity. The main features of this potential are: very transparent even at the nuclear interior and strong dependence with energy of the real and imaginary depths 'V IND. 0' and 'W IND. 0'. At five energies the inelastic scattering data were also analysed and well fitted by coupled-channels calculations. The optical potentials of all channels present the threshold anomaly and are well reproduced by dispersion relation calculations applied to the volume integrals of the optical potentials.
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