Observation of the Lowestp-ShellT=32States ofB11andC11

Abstract

The ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ and ${}_{}{}^{11}{}_{}{}^{}\mathrm{C}$ $T=\frac{3}{2}$ analogs of the ${}_{}{}^{11}{}_{}{}^{}\mathrm{Be}$(0.32-MeV) state have been located utilizing the ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}(p, {}_{}{}^3{}_{}{}^{}\mathrm{He}){}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ and ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}(p, t){}_{}{}^{11}{}_{}{}^{}\mathrm{C}$ reactions. The new states lie at 12.94±0.05 MeV in ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ and at 12.47±0.06 MeV in ${}_{}{}^{11}{}_{}{}^{}\mathrm{C}$, and have total widths of 350±50 and 550±50 keV, respectively; their spins and parities are found to be ${\mathrm{½}}^{-}$. A check on their isospin purity is achieved by examination of their charged-particle decay properties; it is found that the major decay mode is via $L=1\mathrm{}$ isospin-allowed proton emission.