Particle-decaying states of the light nuclei ${}^{11,12}\mathrm{N}$ and ${}^{12}\mathrm{O}$ were studied using the invariant-mass method. The decay energies and intrinsic widths of a number of states were measured, and the momentum correlations of three-body decaying states were considered. A second $2p$-decaying $2^{+}$ state of ${}^{12}\mathrm{O}$ was observed for the first time, and a higher-energy ${}^{12}\mathrm{O}$ state was observed in the $4p+2\alpha$ decay channel. This $4p+2\alpha$ channel also contains contributions from fissionlike decay paths, including ${}^6\mathrm{Be}_{\mathrm{g}.\mathrm{s}.}+{}^6\mathrm{Be}_{\mathrm{g}.\mathrm{s}.}$. Analogs to these states in ${}^{12}\mathrm{O}$ were found in ${}^{12}\mathrm{N}$ in the $2p+{}^{10}\mathrm{B}$ and $2p+\alpha +{}^6\mathrm{Li}$ channels. The momentum correlations for the prompt $2p$ decay of ${}^{12}\mathrm{O}_{\mathrm{g}.\mathrm{s}.}$ were found to be nearly identical to those of ${}^{16}\mathrm{Ne}_{\mathrm{g}.\mathrm{s}.}$, and the correlations for the new $2^{+}$ state were found to be consistent with sequential decay through excited states in ${}^{11}\mathrm{N}$. The momentum correlations for the $2_1^{+}$ state in ${}^{12}\mathrm{O}$ provide a new value for the ${}^{11}\mathrm{N}$ ground-state energy. The states in ${}^{12}\mathrm{N}/{}^{12}\mathrm{O}$ that belong to the $A=12$ isobaric sextet do not deviate from the quadratic isobaric multiplet mass equation form.

• Received 29 May 2019

DOI:https://doi.org/10.1103/PhysRevC.100.024306