Abstract
The {_66^{156}}Dy isotopes in O (6) region were investigated. The positive ground-state band of {_66^{156}}Dy nuclei was also calculated using Interacting Boson Model (IBM-1) and Interacting Vector Boson Model (IVBM). The negative parity band energies of the above isotope have been calculated using (IVBM) only. We Plotd the ratios “ \frac{E(I+2)}{{E(2}_1^+)}, \frac{E(I+2)}{E(I)},\ r(\frac{\left(I+2\right)}{I}) “and the E-GOS curve as a function of the spin (I) to investigate the properties of the yrast band, Accordingly, the best-fit values of parameters are used to construct the Hamiltonian; the electromagnetic transition probability B(E2) of this nucleus is also determined. Theoretical energy levels of Dysprosium-(156) isotope with neutron number N=90 and spin parity up to {30}_1^+ were obtained using the MATLAP-20 simulation program. The comparison of these calculated energy levels with the corresponding experimentally measured ones shows a good agreement between them. Comparing these results with experimental data shows good agreement between them. The results also draw our attention to the fact that the nucleus of interest deforms and exhibits gamma-instability properties.