The energy and width of the well-known 1.75-Mev resonance in the ${\mathrm{C}}^{13}(p, \gamma ){\mathrm{N}}^{14}$ reaction have been investigated by bombarding a thick target of 60% ${\mathrm{C}}^{13}$ with electrostatically-analyzed protons. The resonance energy was determined to be 1746.9±0.8 kev, relative to the ${\mathrm{Li}}^7(p, n){\mathrm{Be}}^7$ threshold at 1881.1 kev. The observed width was 510 ev. When account is taken of the thermal motion of the target atoms, an upper limit to the resonance width may be set at 400 ev; the contribution to this value of the spread in the beam energy is unknown. If one uses the radiation width previously measured by Seagrave ($\omega {\Gamma }_{\gamma }=14.8\mathrm{}$ ev), the resonance cross section is ${\sigma }_R>64\mathrm{}$ mb. The dimensionless reduced proton width (for $d$-waves) is ${{\theta }_p}^2<1.5\mathrm{}\times {10}^{-3\mathrm{}}$.

• Received 10 August 1956

DOI:https://doi.org/10.1103/PhysRev.104.1028