The nuclear levels of ${\mathrm{F}}^{20}$ have been investigated at neutron energies from about 1 to 300 keV. Only a few resonances can be attributed to $s$-wave levels, the remaining ones that can be analyzed being attributable to $p$-wave levels. The two resonances near 27 and 49 keV were investigated extensively and can be attributed to $p$-wave levels. However, the former assumption of mutual interference between this pair of levels was ruled out because their spins of 2 and 1, respectively, appear to be well determined and each resonance exhibits an asymmetrical shape which is just the reverse of what it should be for mutual interference. The cluster of resonances near 100 keV appears to consist of three $p$-wave levels (one each with $J=0, 1$, and 2) and a fourth resonance attributable to an $s$-wave level. Two other small peaks occur on the high-energy side of the cluster. For the levels that could be analyzed, the $s$-wave strength function was found to be small and the $p$-wave one very large. The measurements were made by the method used previously, but the analysis included some recently developed methods.

• Received 28 June 1962

DOI:https://doi.org/10.1103/PhysRev.133.B353