New insights in the first backbending region of heavy Dy isotopes

The7Li-induced incomplete fusion reaction158/160Gd(7Li,p(d,t)xn) (beam energy 56 MeV) has been used to investigate in detail the first backbending region of the heavy stable Dy nuclei160/162Dy. In162Dy, the measured low interaction strength between the ground band and the Stockholm band of |Vgs| ≈ 17 keV confirms the predicted existence of a node in the interaction strength for nuclei with neutron number betweenN = 96 andN = 98, which has not been accessed earlier. The crossing frequency between the ground band and the Stockholm band in162Dy was measured to be hwc = 320 keV, which is about 40 keV higher than the expected value of hwc = 280 keV known from other nuclei in this mass region. In160Dy, an yrare band could be established for the first time in a nucleus with a very large interaction strength. From fits to level energies as well as from branching ratios, an interaction strength of |Vgs| ≈ 220 keV was extracted.