First observation of $^{54}$Zn and its decay by two-proton emission
Résumé
The nucleus $^{54}$Zn has been observed for the first time in an experiment at the SISSI/LISE3 facility of GANIL in the quasi-fragmentation of a $^{58}$Ni beam at 74.5 MeV/nucleon in a $^{nat}$Ni target. The fragments were analysed by means of the ALPHA-LISE3 separator and implanted in a silicon-strip detector where correlations in space and time between implantation and subsequent decay events allowed us to generate almost background free decay spectra for about 25 different nuclei at the same time. Eight $^{54}$Zn implantation events were observed. From the correlated decay events, the half-life of $^{54}$Zn is determined to be 3.2 $\pm$1.8/-0.8 ms. Seven of the eight implantations are followed by two-proton emission with a decay energy of 1.48(2) MeV. The decay energy and the partial half-life are compared to model predictions and allow for a test of these two-proton decay models.