Study of interference nuclear Coulomb the isotopes of germanium.

Author(s)

Marcel Dupret Lopes Barbosa

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Física (IF/SBI)
• Defense date: 2001-09-28

Examining board members

Thereza Borello Lewin; Roberto Meigikos dos Anjos; Frederico Firmo de Souza Cruz; Alinka Lepine; Emerson Jose Veloso de Passos

• Advisor: Thereza Borello Lewin

Abstract

The analysis of the isospin character of the 2 POT.+ IND.1 excitation in the ANTPOT.70,72,74 Ge nuclei, with 28 MeV ANTPOT.6 Li, was applied to the inelastic scattering in the coulomb nuclear interference (CNI) region. The CNI measurements in the exitation of collective states with light isoscalar projectiles are powerful tools to evidence structure changes in nuclei chains, allowing tests of nuclear models. In this method the simultaneous extraction of the charge and mass deformation parameters, minimizes the uncertainties in the ratio of charge B(El) to mass B(ISl) trasition reduced probabilities, wich are important indicators of the nuclear collectivity. The present analysis was developed in the framework of the distorted wave Born approximation within a deformed optical potential approach (DWBA-DOMP), using a set of global optical model parameters. Excellent quality fits of the predictions to the experimental angular distributions, employing the Gauss iterative method, were obtained. The correlated parameters delta IND.N (nuclear deformation length) and C = delta IND.C/delta IND.N (ratio of charge to nuclear deformation lenghts), and their uncertainties extracted in the least squares method, were validated by statistical tests. The B(IS2) values for germanium isotopes, not previously reported, were determined in the analysis and revealed a structure change not evidenced by the B(E2) values. The isoscalar transition reduced probability raises when the neutron number increases, showing in the ANTPOT.74 Ge an abrupt enhancement. Nevertheless, the eletric transition reduced probability grows smoothly. This behavior was detected following the experimental extracted C parameters, indicating in the heavier isotope a predominance of neutrons in the first quadrupolar excitation. The ANTPOT.70,72 Ge isotopes, on the other hand, displayed equivalent and homogeneous contributions of protoons and neutrons. New information on mass and charge contributions for the 0 POT.+ IND.1 -> 2 POT.+ IND.1 transition, in the germanium isotopes, is now available for future theoretical interpretation. (AU)