Quasi-elastic processes of the 48Ca + 120Sn system and the 48Ca nuclear matter density

We present the results of a high-precision quasi-elastic excitation function measurement for the 48Ca + 120Sn system at θLAB = 160 at near-barrier energies in steps of 1.0 MeV. The corresponding quasi-elastic barrier distribution is derived. A large-scale coupled-channel calculation was performed to investigate the role of several reaction channels in the reaction mechanism. An excellent agreement between theory and data was obtained for the barrier distribution. The first quadrupole vibrations of the 48Ca and 120Sn, the 2n, and the 4He transfers have a strong influence on the reaction mechanism and are responsible for the good agreement achieved. The 1n transfer has a minor importance in the result when compared with the 2n transfer, which suggests that the pairing correlation might play an important role in the 2n-neutron transfer process. However, if the octupole vibration of the projectile is included in the coupling scheme, the agreement with the data gets worse. The comparison of the coupled-channel calculations with experimental data leads to the conclusion that the nuclear matter diffuseness of the 48Ca nucleus is 0.56 fm in agreement with most of the double-magic nuclei.European Community 26201

Comprehensive study of reaction mechanisms for the Be9+Sm144 system at near- and sub-barrier energies

The delayed x-ray detection technique was used to measure complete and incomplete fusion cross sections for the $^{9}\mathrm{Be}+^{144}\mathrm{Sm}$ reaction at sub- and near-barrier energies. Elastic and inelastic scattering for this system were also measured. Reaction cross sections were derived and the transfer cross sections of one neutron were calculated. The suppression of complete fusion above the barrier, of the order of 10%, is attributed to $^{9}\mathrm{Be}$ breakup and is considerably smaller than the value of 30% found for the $^{9}\mathrm{Be}+^{208}\mathrm{Pb}$ system

Study Fusion N14 27Al 28Si 29Si

Foram medidas as funções de excitação de fusão de 14N+ 27Al, 14N + 28Si e 14N + 29Si por detecção dos resíduos de evaporação com um telescópio proporcional E-E. Com o objetivo de determinar se a origem da limitação da seção de choque total de fusão em energias intermediárias era devido a propriedades do núcleo composto ou do canal de entrada os resultados experimentais foram interpretados do ponto de vista do: modelo de Horn-Ferguson, modelo de Lozano-Madurga, modelo de Glas-Mosel, modelo da linha de yrast, modelo da linha estatística de yrast, modelo da superposição de níveis, modelo das etapas intermediárias. Foi feita uma discussão da origem destes modelos e um estudo comparativo dos valores que seus parâmetros assumem numa larga faixa de massa inclusive os calculados neste trabalho. Para estes concluímos que existem indicações de que o canal de entrada pode ter influência na limitação da seção de choque de fusão, mas que é necessário medir as reações periféricas nos três sistemas para assegurar esta hipótese.Fusion excitation functions were measured for the systems 14N + 27Al, 14N + 28Si and 14N + 29Si by detecting the evaporation residues with a E-E proportional telescope. Since the principal objective of this work was to determine the roles which the formation of the compound nucleus and the specific properties of entrance channel play in the observed limitations of the total fusion cross section, the experimental results were analyzed in the light of the following models: Horn-Ferguson, Lozano-Madurga, Glas-Mosel, Yrast Line, Statistical Yrast Line, Superposition of Levels, Intermediate Step. The results of these theoretical analyses indicate that the entrance channel exerts some influence on the fusion cross section, but to secure this conclusion it is suggested that measurements on direct reaction mechanisms for these systems be made

Study Fusion N14 27Al 28Si 29Si

Foram medidas as funções de excitação de fusão de 14N+ 27Al, 14N + 28Si e 14N + 29Si por detecção dos resíduos de evaporação com um telescópio proporcional E-E. Com o objetivo de determinar se a origem da limitação da seção de choque total de fusão em energias intermediárias era devido a propriedades do núcleo composto ou do canal de entrada os resultados experimentais foram interpretados do ponto de vista do: modelo de Horn-Ferguson, modelo de Lozano-Madurga, modelo de Glas-Mosel, modelo da linha de yrast, modelo da linha estatística de yrast, modelo da superposição de níveis, modelo das etapas intermediárias. Foi feita uma discussão da origem destes modelos e um estudo comparativo dos valores que seus parâmetros assumem numa larga faixa de massa inclusive os calculados neste trabalho. Para estes concluímos que existem indicações de que o canal de entrada pode ter influência na limitação da seção de choque de fusão, mas que é necessário medir as reações periféricas nos três sistemas para assegurar esta hipótese.Fusion excitation functions were measured for the systems 14N + 27Al, 14N + 28Si and 14N + 29Si by detecting the evaporation residues with a E-E proportional telescope. Since the principal objective of this work was to determine the roles which the formation of the compound nucleus and the specific properties of entrance channel play in the observed limitations of the total fusion cross section, the experimental results were analyzed in the light of the following models: Horn-Ferguson, Lozano-Madurga, Glas-Mosel, Yrast Line, Statistical Yrast Line, Superposition of Levels, Intermediate Step. The results of these theoretical analyses indicate that the entrance channel exerts some influence on the fusion cross section, but to secure this conclusion it is suggested that measurements on direct reaction mechanisms for these systems be made

Study of elastic scattering of \'ANTPOT.16O\' by \'ANTPOT.27 AL\'

Estudo do espalhamento elástico do ANTPOT.16O pelo ANTPOT.27 ALStudy of elastic scattering of \'ANTPOT.16O\' by \'ANTPOT.27 AL\

Study of elastic scattering of \'ANTPOT.16O\' by \'ANTPOT.27 AL\'

Estudo do espalhamento elástico do ANTPOT.16O pelo ANTPOT.27 ALStudy of elastic scattering of \'ANTPOT.16O\' by \'ANTPOT.27 AL\

Dynamic effects of breakup on fusion reactions of weakly bound nuclei

The traditional reduction methods to represent the fusion cross sections of different systems are flawed when attempting to completely eliminate the geometrical aspects, such as the heights and radii of the barriers, and the static effects associated with the excess neutrons or protons in weakly bound nuclei. We remedy this by introducing a new dimensionless universal function, which allows the separation and disentanglement of the static and dynamic aspects of the breakup coupling effects connected with the excess nucleons. Applying this new reduction procedure to fusion data of several weakly bound systems, we find a systematic suppression of complete fusion above the Coulomb barrier and enhancement below it. Different behaviors are found for the total fusion cross sections. They are appreciably suppressed in collisions of neutron-halo nuclei, while they are practically not affected by the breakup coupling in cases of stable weakly bound nuclei. (C) 2009 Elsevier B.V. All rights reserved.Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ)FAPERJCNPqConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESPConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)PRONE

Disentangling static and dynamic effects of low breakup threshold in fusion reactions

A new technique to analyze fusion data is developed. From experimental cross sections and results of coupled-channel calculations a dimensionless function is constructed. In collisions of strongly bound nuclei this quantity is very close to a universal function of a variable related to the collision energy, whereas for weakly bound projectiles the effects of breakup coupling are measured by the deviations with respect to this universal function. This technique is applied to collisions of stable and unstable weakly bound isotopes.FAPERJFundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)CNPqFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESPConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)PRONE