Study of the Nuclear Fusion and the Polarization Potential for Heavy-Ions Systems

Author(s)

Gustavo Pires de Almeida Nobre

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Física (IF/SBI)
• Defense date: 2007-06-21

Examining board members

Luiz Carlos Chamon; Edilson Crema; Sérgio José Barbosa Duarte; Antonio Fernando Ribeiro de Toledo Piza; Jesus Lubian Rios

• Advisor: Luiz Carlos Chamon

Abstract

In this Ph.D. thesis two theoretical models (ZPM and GFA) were proposed in order to obtain fusion cross sections and one (ZPM) to calculate the polarization potential for the elastic channel and the corresponding scattering cross section. The São Paulo (SP) potential, which has as one of its main characteristics the complete absence of adjustable parameters, was used as bare interaction in the calculations of the present work. Therefore, all results, presented in the context of different models, correspond to theoretical predictions instead of simply data fit. After a comparative analysis of fusion calculations, the GFA and ZPM models demonstrated to be equivalents and compatible with the usual coupled channel calculations, with the advantage of incorporating inelastic couplings to the complete vibrational band and of providing accurate fusion cross sections at extreme low energies relative to the Coulomb barrier. We applied the ZPM model to the calculation of the fusion excitation function for 112 heavy-ion systems, involving not only even-even nuclei but also odd-even and odd-odd ones (including some weakly-bound nuclei), and we compared the theoretical results with experimental data existing in literature. While the usual non-deformed barrier penetration model provides enhancements up to eleven orders of magnitude, the ZPM model predictions are in good agreement with the data within only two orders of magnitude. When confronting the ZPM model results with experimental data of elastic scattering cross sections for some systems, at energies around the Coulomb barrier, we found out good agreement between them. Therefore, we demonstrated that it is possible to treat the elastic scattering and fusion channels in a consistent manner, within the same context. (AU)