Competition between $beta$-delayed proton and $beta$-delayed $gamma$ decay of the exotic $T_z$ = -2 nucleus $^{56}$Zn 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 $T_z$ = -2 nucleus $^{56}$Zn. Three $gamma$-proton sequences have been observed following the $beta$ 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 $gamma$ 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 $^{56}$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.

$beta$-delayed $gamma$-proton decay in $^{56}$Zn: analysis of the charged-particle spectrum

A study of the $beta$ decay of the proton-rich $T_{z}$ = -2 nucleus $^{56}$Zn has been reported in a recent publication. A rare and exotic decay mode, $beta$-delayed $gamma$-proton decay, has been observed there for the first time in the $fp$ shell. Here we expand on some of the details of the data analysis, focussing on the charged particle spectrum.

Observation of the $beta$-delayed $gamma$-proton decay of $^{56}$Zn and its impact on the Gamow Teller strength evaluation

We report the observation of a very exotic decay mode at the proton drip-line, the $beta$-delayed $gamma$-proton decay, clearly seen in the $beta$ decay of the $T_z$ = -2 nucleus $^{56}$Zn. Three $gamma$-proton sequences have been observed after the $beta$ decay. Here this decay mode, already observed in the $sd$-shell, is seen for the first time in the $fp$-shell. Both $gamma$ and proton decays have been taken into account in the estimation of the Fermi (F) and Gamow Teller (GT) strengths. Evidence for fragmentation of the Fermi strength due to strong isospin mixing is found.

Beta Decay Of Exotic Tz = -1 And Tz = -2 Nuclei

The half-lives of the Tz = -2, 56Zn and Tz = -1, 58Zn isotopes and other nuclei were measured in a {beta}-decay experiment at GANIL. The energy levels populated by the 56Zn {beta} decay were determined. The 56Zn results are compared with the results of the mirror process, the charge exchange reaction 56Fe(3He,t)56Co.