The second excited state ${(J}^{\pi }{=1/2\mathrm{}}^{+},$ $\mathcal{l}=0)$ of the proton-rich nucleus ${}^{19}\mathrm{Na}$ has been observed for the first time using the elastic scattering reaction ${}^1\mathrm{H}{(}^{18}\mathrm{Ne}{,}^1\mathrm{H}{)}^{18}\mathrm{Ne}.$ An intense $(4\mathrm{}\times {10}^6\mathrm{pps})$ ${}^{18}\mathrm{Ne}$ radioactive beam was produced at the CRC-RIB facility at Louvain-la-Neuve to bombard a polyethylene target. The recoil protons were detected at 20 different angles in the LEDA segmented silicon detector. The resulting elastic scattering cross sections have been analyzed using a global R-matrix fit. We find that the second excited state in ${}^{19}\mathrm{Na}$ lies at the center-of-mass energy $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=1.066\mathrm{}\pm 0.003\mathrm{MeV}$ with respect to the ${}^{18}\mathrm{Ne}+p$ threshold, and has a proton width ${\Gamma }_{\mathrm{p}}=101\mathrm{}\pm 3\mathrm{}\mathrm{keV}.$ The Coulomb shift between the ${1/2}^{+}$ mirror levels in ${}^{19}\mathrm{O}$ and ${}^{19}\mathrm{Na}$ is 0.73 MeV, among the largest values currently observed in light exotic nuclei.

• Received 29 July 2002

DOI:https://doi.org/10.1103/PhysRevC.67.014308