Competition between beta-delayed proton and gamma-delayed decay of the exotic Tz = -2 nucleus 56Zn and fragmentation of the IAS

A very exotic decay mode at the proton drip-line, beta-delayed gamma-proton decay, has been observed in the beta decay of the Tz = -2 nucleus 56Zn. Three gamma-proton sequences have been observed following the beta decay. The fragmentation of the IAS in 56Cu has also been observed for the first time. The results were reported in a recent publication. At the time of publication the authors were puzzled by the competition between proton and gamma decays from the main component of the IAS. Here we outline a possible explanation based on the nuclear structure properties of the three nuclei involved, namely 56Zn, 56Cu and 55Ni, close to the doubly magic nucleus 56Ni. From the fragmentation of the Fermi strength and the excitation energy of the two populated 0+ states we could deduce the off-diagonal matrix element of the charge-dependent part of the Hamiltonian responsible for the mixing. These results are compared with the decay of 55Cu with one proton less than 56Zn. For completeness we summarise the results already published.