Large-Scale Shell Model Investigation of Even-Even 66-76Ni Isotopes

Fouad A. Majeed, Fatima M. Hussain, Ali ObiesMuhsen Almayyali

1Department of Physics College of Education for Pure Sciences, University of Babylon, Babylon- Iraq


Abstract: The structure of neutron-rich even-even 66-76Ni have been investigated by means of large-scale shell-model calculations. The energy levels for positive and negative parity states and the reduced transition probabilities B(E2;???? ? ????)are calculated by using the shell model code Nushellxby employing the effective interactions jun45 and jj44b. The results for excitation energies and reduced transition probabilities are compared with the recent available experimental data. Reasonable agreement is obtained for all isotopes under study.

Keywords: Shell model, energy levels, transition probabilities, Nushellx


1. Introduction

The nuclear shell model has been very successful in our understanding of nuclear structure: once a suitable effective interaction is found, the shell model can predict various observables accurately and systematically [1]. For light nuclei, there are several “standard” effective interactions such as the Cohen-Kurath [2].The nickel isotopes (Z = 28) cover three doubly-closed shells with number N = 38,to N = 48 have been described by state-of-the-art shell model calculations with two recently available interactions using 56Ni as a core in the f5/2pg9/2 model space and therefore a unique testing ground to investigate the evolution of shell structure. The 66Ni and its neighboring attracted the interest of recent research to answer the magicity versus superfluidity question related to doubly magic character of this nuclei[3,4,5,6,7]. Srivastava[8], performed shell model calculations for Ni, Cu and Zn isotopes by modifying the fpg interaction by modifying 28 two-body matrix element of the earlier interaction, the new interaction codenamed fpg9a is tuned for Cu isotopes and tested for Ni and Zn isotopes. Very recently F. Recchia et al. [9] investigated the level structure of 68Ni by two-neutron knockout and multi-nucleon-transfer reaction and they compare their experimental finding with the shell model calculations using several modern effective interactions. Y. Tsunoda [10], studied the shapes of neutron-rich exotic Ni isotopes by performing large-scale shell model calculations by the advanced Monte Carlo shell model (MCSM) in which the experimental energy levels are well described by using a single fixed Hamiltonian. In this research we report the shell model calculations in the fpg-shell region for the even-even 66-76Ni isotopes by employing the modern jun45 [11] and jj44b [12] effective interactions, to test the ability of the present effective interactions to reproduce the experiment in this mass region.
2. Shell Model Calculation
The independent-particle Hamiltonian of an A-particle system can be written in terms two-particle interactions as