Studies on ${\mathrm{F}}^{19}$ in the ${\mathrm{O}}^{18}(p, \gamma ){\mathrm{F}}^{19}$ Reaction

Studies of the ${\mathrm{O}}^{18}(p, \gamma ){\mathrm{F}}^{19}$ reaction at the 849-keV resonance have established decay schemes for the 8.76-MeV resonance level and also for the 3.91-MeV level which is populated through de-excitation of the former by an 18% branch. Angular-correlation measurements establish a $J=\frac{3}{2}$ assignment for the 3.91-MeV level. A level of this spin assignment is not predicted by the intermediate-coupling shell models, but all collective models which have been applied to ${\mathrm{F}}^{19}$ and which imply a strong prolate deformation of the nucleus have predicted a ${\frac{3}{2}}^{+}$ state in this energy region. Selection rules based on the asymptotic Nilsson model provide an excellent description of the de-excitation branching ratios for both the 8.76- and the 3.91-MeV state as studied herein, demonstrating the utility of these rules even in so light a nucleus. Additional measurements at the 1169-keV resonance have determined the decay scheme for the 9.07-MeV resonance level, which deexcites strongly through the 2.79-MeV level. The limitation $J=\frac{5}{2} or \frac{9}{2}$ on possible spin assignments for the 2.79-MeV level is confirmed; however, simple angular-distribution measurements cannot distinguish between these two possibilities.