A double vacuum, configuration dependent pairing and lack of β-vibrations in transitional nuclei: Band structure of N = 88 to N = 91 Nuclei Original Research Article

We have used the AFRODITE γ-ray spectrometer to measure yrare structures in 152,154,155Gd using (α,xn) reactions. The measurements on 152,154Gd have shown that there is no convincing evidence that the lowest excited View the MathML source states are β-vibrations based on the View the MathML source ground state. Rather these levels may be regarded as a “second vacuum” each with its own γ and octupole vibrations. This is confirmed by the blocking of the coupling of this core View the MathML source state in 154Gd to the [505]11/2− single-particle quasi-neutron orbital in 155Gd. The coupling of this orbital to the 2+γ-vibration is observed since this coupling is not Pauli-blocked.