Study of the Low-Lying Levels of ${\mathrm{F}}^{18}$ by Means of the ${\mathrm{O}}^{16}({\mathrm{He}}^3, p\gamma ){\mathrm{F}}^{18}$ Reaction

The particle-gamma angular-correlation method of Litherland and Ferguson was used to gain information on the decay modes and spin assignments of the first ten excited states of ${\mathrm{F}}^{18}$. The ${\mathrm{O}}^{16}({\mathrm{He}}^3, p){\mathrm{F}}^{18}$ reaction was used with ${\mathrm{He}}^3$ energies between 3.0 and 4.2 MeV. Protons were detected in an annular counter at 180° to the beam and gamma rays were detected at angles between 0° and 90° to the beam. Decay modes are given for all ten states of ${\mathrm{F}}^{18}$ below 3.5-MeV excitation. Spin assignments of (0,1,2), 1, (1,2), 2, 1, and (2,3) were established for the levels at 1.08, 1.70, 2.10, 2.53, 3.13, and 3.35 MeV. The present results combined with previous work lead to an assignment of $3^{+}$ for the 0.940-MeV level, a most probable assignment of 2 for the 3.06-MeV level, and $2^{+}$ for the 2.53-MeV level. Dipole-quadrupole or quadrupole-octupole mixing ratios were obtained for some of the gamma-ray transitions. The results are compared with previous shell-model predictions.