Blocking of coupling to the 02 + excitation in 154Gd by the [505]11/2- neutron in 155Gd

Abstract

The concept that the first excited 0+ states in N = 90 nuclei are not a $ \beta$ -vibration but a second vacuum formed by the combination of the quadrupole pairing force and the low density of oblate orbitals near the Fermi surface is supported by the blocking of this collective mode in 154Gd from coupling to the [505]11/2- single-particle quasi-neutron orbital in 155Gd . The coupling of this orbital to the 2+ $ \gamma$ -vibration in 154Gd is observed since this coupling is not Pauli-blocked.