The ${\mathrm{N}}^{14}(\alpha ,\gamma ){\mathrm{F}}^{18}$ reaction has been studied over the range of bombarding energies from 1.00 to 1.70 MeV. In addition to the well-known resonances at 1.53 and 1.62 MeV, two new resonances have been found at $\alpha$-particle energies of 1.140±0.005 MeV and 1.395±0.005 MeV, corresponding to excited states in ${\mathrm{F}}^{18}$ at energies of 5.290 and 5.490 MeV, respectively. The branching ratio for the $\gamma$ decay of the 5.29-MeV state was determined as 5.290 → 2.524 [(87±3)%] and 5.290 → 0.937 [(13±3)%]. The quantity $\frac{\mathrm{}(2J+1)\mathrm{}{\Gamma }_{\gamma }{\Gamma }_{\alpha }}{\Gamma }$ for the total electromagnetic decay of each of these four resonances was determined as 0.084±0.004 eV (1.140 MeV), 0.027±0.003 eV (1.395 MeV), 4.80±0.40 eV (1.53 MeV), and 1.35±0.15 eV (1.62 MeV), respectively. On the basis of the observed lack of nonresonant yield from the ${\mathrm{N}}^{14}(\alpha ,\gamma ){\mathrm{F}}^{18}$ reaction in this energy region, it is possible to establish an upper limit on the nonresonant $S$ factor for this reaction, $S\le 1.5\times {10}^6$ keV b.

• Received 22 May 1968

DOI:https://doi.org/10.1103/PhysRev.173.1021