The reaction ${\mathrm{O}}^{16}({\mathrm{He}}^3, p){\mathrm{F}}^{18}$ has been employed to study the de-excitation gamma-ray branching of levels in ${\mathrm{F}}^{18}$ up to about 3 Mev using $p\gamma$ coincidence techniques. These measurements have been shown to be in reasonable agreement with tentative level identifications, 0 Mev (1+), 0.94 Mev (3+), 1.04 Mev (0+, $T=1\mathrm{}$), 1.12 Mev (5+), 1.70 Mev (1+), 2.10 Mev (2+), 2.53 Mev (3+), and 3.06 or 3.13 Mev unresolved (2+, $T=1\mathrm{}$), based on the intermediate-coupling shell-model predictions of Elliott and Flowers and of Redlich. An additional level at 1.08 Mev, which may arise from core excitation, is shown likely to have spin zero. It is suggested that the predicted energies need to be reduced by a factor of 0.6 and that the $T=1\mathrm{}$ levels require shifting with respect to the $T=0\mathrm{}$ levels to bring them into agreement with experiment. It has not been found possible to obtain an adequate fit to the ${\mathrm{F}}^{18}$ level spectrum presented in terms of a rotational collective model. The data, may, however, be qualitatively in accord with an alpha-${\mathrm{N}}^{14}$ cluster model interpretation. An example of the isotopic spin selection rule inhibiting $\Delta T=0\mathrm{}$ $M1\mathrm{}$ transitions in self-conjugate nuclei has been found.

• Received 16 December 1960

DOI:https://doi.org/10.1103/PhysRev.122.908