Radioactive ion beams of ${}^{17}\mathrm{F}$ were used to study several resonance states in ${}^{18}\mathrm{Ne}$. Clear evidence for simultaneous two-proton emission from the 6.15 MeV state $\left(J^{\pi }{=1\mathrm{}}^{-}\right)$ in ${}^{18}\mathrm{Ne}$ has been observed with the reaction ${}^{17}\mathrm{F}{+}^1\mathrm{H}$. Because of limited angular coverage, the data did not differentiate between the two possible mechanisms of simultaneous decay, diproton ${(}^2\mathrm{He})$ emission or direct three-body decay. The two-proton partial width was found to be $21\pm 3\mathrm{eV}$ assuming ${}^2\mathrm{He}$ emission and $57\pm 6\mathrm{eV}$ assuming three-body decay. The total width of the $1^{-}$ state was measured to be $50\pm 5\mathrm{keV}$. Several additional resonances that decay by single proton emission were also studied.

• Received 10 July 2000

DOI:https://doi.org/10.1103/PhysRevLett.86.43