Gamow-Teller strength in theO18(p, n)F18reaction at 135 MeV

The distribution of Gamow-Teller strength in the ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}(p, n){}_{}{}^{18}{}_{}{}^{}\mathrm{F}$ reaction was studied at a bombarding energy of 135 MeV. Five $1^{+}$, $T=0\mathrm{}$ states are identified below $E_x=7\mathrm{}$ MeV and a concentration of $1^{+}$ states of presumed $T=1\mathrm{}$ character is observed between $E_x=9.5\mathrm{} \mathrm{and} 12$ MeV. Approximately 82% of the $1^{+}$ strength is concentrated into the ground-state transition and only 5.5% is seen in the $T=1\mathrm{}$ component. Normalization of the ground-state transition to the known Gamow-Teller matrix element from the analogous beta decay of ${}_{}{}^{18}{}_{}{}^{}\mathrm{Ne}$ allows the ($p, n$) cross sections to be related to the Gamow-Teller strength. The resulting total Gamow-Teller strength observed in the ($p, n$) reaction is about two-thirds of the minimum value required by the sum rule for a $T=1\mathrm{}$ nucleus. This result is in reasonable agreement with the total Gamow-Teller strength predicted from a shell-model calculation which uses empirically renormalized single-particle Gamow-Teller matrix elements. The concentration of the $T=0\mathrm{}$ strength predominantly into the ground state and the observed ratio of $T=1\mathrm{}$ to $T=0\mathrm{}$ strength also are consistent with these calculations.