Evidence for an Isomeric 3/2- State in 53Co

The fragmentation of a 550MeV/u primary beam of 58Ni on a 9Be target has been used to measure time- and energy-correlated γ decays following the implantation of event-by-event discriminated secondary fragments into a 9Be stopper plate. A new isomeric γ decay with T 1/2 = 14(\( \begin{smallmatrix}6 4\end{smallmatrix}\)) ns and E γ = 646.2(2) keV is observed and attributed to the decay of the yrast 3/2- state in 53 27Co26 . This short-lived isomeric state has been populated by means of nuclear reactions during the stopping process of the secondary fragments. The experimental findings are discussed in the framework of large-scale spherical shell model calculations in conjunction with isospin symmetry-breaking residual interactions for the A = 53 , T z = ±1/2 mirror nuclei 53Co and 53Fe .