Competition between ${\hat{I}}^2$-delayed proton and ${\hat{I}}^2$-delayed ${\hat{I}}^3$ decay of the exotic $T_z$ = -2 nucleus ${}^{56}$Zn and fragmentation of the IAS

Abstract

A very exotic decay mode at the proton drip-line, ${\hat{I}}^2$-delayed ${\hat{I}}^3$-proton decay, has been observed in the ${\hat{I}}^2$ decay of the $T_z$ = -2 nucleus ${}^{56}$Zn. Three ${\hat{I}}^3$-proton sequences have been observed following the ${\hat{I}}^2$ decay. The fragmentation of the IAS in ${}^{56}$Cu 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 ${\hat{I}}^3$ 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 ${}^{56}$Zn, ${}^{56}$Cu and ${}^{55}$Ni, close to the doubly magic nucleus ${}^{56}$Ni. 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 ${}^{55}$Cu with one proton less than ${}^{56}$Zn. For completeness we summarise the results already published.

Proceedings of the 2nd Conference on Advances in Radioactive Isotope Science ARIS2014. 6 pages, 4 figures