Particle-hole stretched states excited in the 26Mg(p,n)26Al reaction at 134 MeV.

Abstract

Strong excitation of both (\ensuremath{\pi}${d}_{5/2}$,\ensuremath{\nu}${d}_{5/2}^{\mathrm{\ensuremath{-}}1}$) ${5}^{+}$, 0 \ensuremath{\Elzxh}\ensuremath{\omega} and (\ensuremath{\pi}${f}_{7/2}$,\ensuremath{\nu}${d}_{5/2}^{\mathrm{\ensuremath{-}}1}$) ${6}^{\mathrm{\ensuremath{-}}}$, 1 \ensuremath{\Elzxh}\ensuremath{\omega} stretched-state strength is observed in the $^{26}(\mathit{p}$,n${)}^{26}$Al reaction at 134.4 MeV. The T=0, ${5}^{+}$ strength is observed to be predominantly in the ground state which has 56% of the strength predicted by a distorted-wave impulse approximation calculation that assumes the extreme single-particle-hole model. Another 17% of this strength is observed in a ${5}^{+}$ state at 3.4 MeV. The ${6}^{\mathrm{\ensuremath{-}}}$ strength is split into three isospin components: 61% of the extreme single-particle-hole model T=0, ${6}^{\mathrm{\ensuremath{-}}}$ strength is observed in three states between 6.9 and 11.0 MeV; 58% of the predicted T=1 strength is observed in nine states between 9.3 and 16.5 MeV; 27% of the predicted T=2 strength is observed in a single state at 18.2 MeV. The observed ${6}^{\mathrm{\ensuremath{-}}}$-state excitation energies are in general agreement with the T=0 and 1, ${6}^{\mathrm{\ensuremath{-}}}$ states observed in the $^{25}(\mathit{\ensuremath{\alpha}}$,t${)}^{26}$Al reaction and with the analog T=1 and 2, ${6}^{\mathrm{\ensuremath{-}}}$ states in $^{26}\mathrm{Mg}$ observed in inelastic electron and proton scattering. The total observed ${5}^{+}$ strength and its distribution are in good agreement with distorted-wave impulse approximation calculations that use full S-D shell-model wave functions. The total ${6}^{\mathrm{\ensuremath{-}}}$ strength and its distribution are generally indicated by a shell-model calculation that assumes only 2p2h correlations in the $^{26}\mathrm{Mg}$ target nucleus and requires one particle in the 1${f}_{7/2}$ orbital for the final ${6}^{\mathrm{\ensuremath{-}}}$ states; quantitatively, the calculation predicts less fragmentation than observed.