Energy levels in the nucleus 156Dy through the 159Tb(p, 4nγ)156Dy reaction

Using the ¹⁵⁹Tb(p, 4nγ)¹⁵⁶Dy reaction at E_p = 27 to 51 MeV and standard on-line γ-ray spectroscopy methods, the energies and decay properties of members of various rotational bands in the nucleus ¹⁵⁶Dy have been investigated, i.e. the ground-state band up to 14_g⁺, the β-vibrational band up to 14_β⁺,the γ-vibrational band up to 11_γ⁺,and two other bands, one with odd-spin levels up to 11, the other with even-spin levels up to 10. The results are compared with various calculations in the framework of the collective model, and no satisfactory fit is obtained; possible improvements of the model to remove these discrepancies are suggested.