Study of phase transitions and critical points in the rare-earth region in the framework of the interacting boson model (IBM-1). +CD

number: 
1037
English
department: 
Degree: 
Imprint: 
Physics
Author: 
Fouad Attia Majeed Al-Ajeeli
Supervisor: 
Dr.Ra'ad A. Radhi
Dr.Siham A. Kandela
Dr.Saddon T. Ahmad
year: 
2005
Abstract:

A systematic study of isotope chains in the rare_earth region is presented. For the chains 144, , , and 150, energy levels, E2 transition rates, and two_neutron separation energies (SNd15460-Sm16014662-Gd16214864-Dy16666-2n) are described by using the most general (up to two_body terms) IBM-1 Hamiltonian. For each isotope chain a general fit is performed in such a way that all parameters but one are kept fixed to describe the whole chain. In this region, nuclei evolve from spherical to deformed shapes and a method based on catastrophe theory, in combination with a coherent state analysis to generate the IBM-1 energy surfaces, is used to identify critical phase transition points. The approach used to fix the Hamiltonian parameters leads to a very good global agreement with the recent available experimental data corresponding to excitation energies, B(E2)_s and S2n values. In particular, an excellent agreement with the measured S2n values is obtained, which is considered a key observable to locate phase transitional regions. The analysis presented here is consistent with previous CQF studies in the same region. As a result we find that 148Nd and 150Sm are the best candidates to be critical, but we should remark that 150Nd and 152Sm are not far away from it.