Two-quasiparticle isomers and bands of Nd-154,Nd-156 and Sm-156,Sm-158,Sm-160

The decay of a new 3.2-μs, (4−) isomeric state at 1298.0 keV has been observed using γ -ray spectroscopy at the Lohengrin mass spectrometer of the Institut Laue-Langevin. By comparison with theoretical calculations this state was assigned a ν5/2[642] ⊗ ν3/2[521] dominant configuration. Prompt γ -ray data from a spontaneous fission experiment have also been analyzed allowing the observation of a collective band on top of this isomeric state, the identification of a new band on top of the previously reported (5−) isomer of 156Nd and the extension of collective bands on top of (5−) isomers of the neighboring 156,158Sm nuclei. Quasiparticle rotor model calculations reported in this work correctly predict the energies and decay patterns of these bands. A new (5−) isomer in 160Sm has also been observed. The calculations predict ν5/2[642] ⊗ ν5/2[523] dominant configurations for all these (5−) isomers