We report on the first observation of the unbound proton-rich nucleus ${}^{15}\mathrm{Ne}$. Its ground state and first excited state were populated in two-neutron knockout reactions from a beam of 500 MeV/u ${}^{17}\mathrm{Ne}$. The ${}^{15}\mathrm{Ne}$ ground state is found to be unbound by 2.522(66) MeV. The decay proceeds directly to ${}^{13}\mathrm{O}$ with simultaneous two-proton emission. No evidence for sequential decay via the energetically allowed $2^{-}$ and $1^{-}$ states in ${}^{14}\mathrm{F}$ is observed. The ${}^{15}\mathrm{Ne}$ ground state is shown to have a strong configuration with two protons in the ($sd$) shell around ${}^{13}\mathrm{O}$ with a 63(5)% $(1s_{1/2}{)}^2$ component.

• Received 17 January 2014

DOI:https://doi.org/10.1103/PhysRevLett.112.132502