Measurements of the fusion barrier distributions for the systems 16,18 O+56,58 Ni

Author(s)

Rone Flávio Simões

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Física (IF/SBI)
• Defense date: 2002-11-06

Examining board members

Edilson Crema; Paulo Roberto Silveira Gomes; Alinka Lepine; Maria Carolina Nemes; Dirceu Pereira

• Advisor: Edilson Crema

Abstract

Excitation functions for quasi-elastic scattering were measured with high precision with energy steps of 500 keV for the 16,18O + 56,60Ni systems. Fusion barrier distributions were extracted from the excitation functions. Coupled channel calculations were used in order to determine which channels are responsible for the structures observed in the experimental distributions. Two computation codes were used: CCFULL and FRESCO. Their results are similar. We compared Dfus with Dqe obtained with FRESCO and we have concluded that they are practically identical for all systems. This is a confirmation that the approximation Dfus = Dqe is reasonable in this mass region. The first conclusion with CCFULL code is that alpha stripping for the 16O + 58Ni system is the channel transfer most important at above barrier energies. However, the calculation with FRESCO showed that it has only minor importance. For the 16O + 60Ni system, the more expressive transfer channel is alpha pick-up. In the two other systems, 18O + 58,60Ni, we observed that one-neutron stripping has Strong influence on the barrier distributions. Beside the transfer channels, the target inelastic excitation is a very important reaction channel in all systems. (AU)