Structure and 2p decay mechanism of ¹⁸Mg

The recently discovered, extremely proton-rich nuclide \(^{18}\) $_{}^{18}$ Mg exhibits ground-state decay via two sequential two-proton (2p) emissions through the intermediate nucleus, \(^{16}\) $_{}^{16}$ Ne. This study investigates the structure and the initial 2p decay mechanism of \(^{18}\textrm{Mg}\) $_{}^{18}\text{Mg}$ by examining the density and correlations of the valence protons using a three-body Gamow coupled-channel method. The results show that the ground state of \(^{18}\textrm{Mg}\) $_{}^{18}\text{Mg}$ is significantly influenced by the continuum, resulting in a significant s-wave component. However, based on the current framework, this does not lead to a significant deviation in mirror symmetry in either the structure or spectroscopy of the \(^{18}\textrm{Mg}\) $_{}^{18}\text{Mg}$ – \(^{18}\textrm{C}\) $_{}^{18}\text{C}$ pair. Additionally, the time evolution analysis of the \(^{18}\textrm{Mg}\) $_{}^{18}\text{Mg}$ ground state suggests a simultaneous 2p emission during the first step of decay. The observed nucleon–nucleon correlations align with those of the light-mass 2p emitters, indicating a consistent decay behavior within this nuclear region.