Beta-decay study of $T_z=-2$ proton-rich nucleus ${}^{20}$Mg

Abstract

The ${\hat{I}}^2$ decay of the drip-line nucleus ${}^{20}$Mg gives important information on resonances in ${}^{20}$Na, which are relevant for the astrophysical $rp$-process. A detailed ${\hat{I}}^2$ decay spectroscopic study of ${}^{20}$Mg was performed by a continuous-implantation method. A detection system was specially developed for charged-particle decay studies, giving improved spectroscopic information including the half-life of ${}^{20}$Mg, the excitation energies, the branching ratios, and the log $ft$ values for the states in ${}^{20}$Na populated in the ${\hat{I}}^2$ decay of ${}^{20}$Mg. A new proton branch was observed and the corresponding excited state in ${}^{20}$Na was proposed. The large isospin asymmetry for the mirror decays of ${}^{20}$Mg and ${}^{20}$O was reproduced, as well. However, no conclusive conclusion can be draw about the astrophysically interesting 2645~keV resonance in ${}^{20}$Na due to the limited statistics.