We have studied ${}_{}{}^{18}{}_{}{}^{}\mathrm{Ne}$ states up to 9 MeV excitation energy via the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$(${}_{}{}^3{}_{}{}^{}\mathrm{He}$,$n$)${}_{}{}^{18}{}_{}{}^{}\mathrm{Ne}$ and ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$($p$,$t$)${}_{}{}^{18}{}_{}{}^{}\mathrm{Ne}$ reactions. Excitation energies, widths, absolute cross sections, and angular distributions were measured. Distorted-wave Born approximation calculations were performed for comparison with the (${}_{}{}^3{}_{}{}^{}\mathrm{He}$,$n$) angular distributions and the ($p$,$t$) data were compared with previous calculations. Members of the 4.5-MeV doublet were found to have excitation energies of 4.518 ± 0.008 and 4.590 ± 0.008 MeV with spin and parity $1^{-}$ and $0^{+}$, respectively. The 5.1-MeV group was resolved into a doublet with 5.090 ± 0.008 and 5.144 ± 0.008 MeV excitation energies. Several previously unidentified states were found at excitation energies greater than 5 MeV, including a state at 7.062 ± 0.012 MeV that is strongly populated via (${}_{}{}^3{}_{}{}^{}\mathrm{He}$,$n$), but not observed in ($p$,$t$). We calculated two-particle Coulomb energy shifts for model mass-18 $T=1\mathrm{}$ states and found that the difference between the excitation energy of the 4.59-MeV $0^{+}$ state and the analogous state at 5.34 MeV in ${}_{}{}^{18}{}_{}{}^{}0$ gives strong evidence for the predominantly ${s_{\frac{1}{2}}}^2$ character of the state.

NUCLEAR REACTIONS, NUCLEAR STRUCTURE ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$(${}_{}{}^3{}_{}{}^{}\mathrm{He}$,$n$)${}_{}{}^{18}{}_{}{}^{}\mathrm{Ne}$, $E=10-22\mathrm{}$ MeV; measured $\sigma (E_n,\theta )$. ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$($p$,$t$)${}_{}{}^{18}{}_{}{}^{}\mathrm{Ne}$, $E=41.8\mathrm{}$ MeV; measured $\sigma (E_t,\theta )$. Gas targets. DWBA analysis. Deduced ${}_{}{}^{18}{}_{}{}^{}\mathrm{Ne}$ levels, J, $\pi$. Calculated Coulomb shifts for model mass 18 $T=1\mathrm{}$ states.

• Received 30 July 1980

DOI:https://doi.org/10.1103/PhysRevC.24.1864