Spectroscopy of ${}_{}{}^{16}{}_{}{}^{}\mathrm{F}$ from the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$($p$,$n$)${}_{}{}^{16}{}_{}{}^{}\mathrm{F}$ reaction at 99 and 135 MeV

We measured neutron energy spectra and extracted angular distributions for eleven separate transitions for the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$($p$,$n$)${}_{}{}^{16}{}_{}{}^{}\mathrm{F}$ reaction at 99.1 and 135.2 MeV. Several new spin and parity assignments are obtained for states in ${}_{}{}^{16}{}_{}{}^{}\mathrm{F}$ by comparison of the excitation energy spectra with known analog states in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and with a shell-model prediction and by analysis of the neutron angular distributions. The most strongly-excited states are two $2^{-}$ states at $E_x=0.40\mathrm{}\pm 0.05 \mathrm{and} 7.6\pm 0.1$ MeV, a $4^{-}$ state at 6.37±0.05 MeV, and two broad $1^{-}$ states at 9.4±0.1 and 11.5±0.1 MeV. These states are analogs of known $2^{-}$ ($M2$) states, a $4^{-}$ "stretched" state, and $1^{-}$ ($E1$) strength, respectively, in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$. Three weakly excited $1^{+}$ states are observed at $E_x=3.75\mathrm{}\pm 0.05, 4.65\pm 0.05, \mathrm{and} 6.23\pm 0.05$ MeV. These states are analogs of known $1^{+}$ ($M1$) states in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and directly indicate correlations in the ground state of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$. A weakly excited $4^{-}$ state is seen at 5.93±0.05 MeV in good agreement with a $4^{-}$ state observed in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ ($e$,$e^{\prime }$) measurements. All of the most strongly excited states align (to within ±200 keV) with known $T=1\mathrm{}$ analog states in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ for a common net displacement energy of 12.6 MeV. The ($p$,$n$) reaction at medium energies is shown to be an important spectroscopic tool.

NUCLEAR REACTIONS ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$($p$,$n$)${}_{}{}^{16}{}_{}{}^{}\mathrm{F}$, $E=99.1\mathrm{} \mathrm{and} 135.2$ MeV; measured neutron spectra in ∼3° steps between 0° and 69°; extracted $\sigma \left(\theta \right)$ for eleven separate transitions to discrete states in ${}_{}{}^{16}{}_{}{}^{}\mathrm{F}$. Compared excitation energies with analog states in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and with a shell-model prediction. Deduced several new $J^{\pi }$ assignments.