Search

The collectivity of the odd-mass nucleus 55 Ni was explored via intermediate-energy Coulomb excitation using a powerful combination of particle and g -ray spectroscopy. A g -ray at 2879 ( 18 ) keV was observed and is interpreted to deexcite a member of the core-coupled quintuplet 2 1 + s 56 Ni d ^ n f 7/2 −1 at the same energy. By similarity with the mirror nucleus 55 Co, transition probabilities were calculated assuming J p =9/2 − and J p =11/2 − for this state. Both assumptions lead to a transition strength higher than predicted by a large-scale shell-model calculation using the GXPF1 effective interaction and exceed the value predicted within a simple weak-coupling approach ispartof: Physical Review C, Nuclear Physics vol:70 issue:6 status: published