The total ($p, n$) reaction cross sections, integrated over the $4\pi$ solid angle and summed over all neutron groups, for ${}_{}{}^{50}{}_{}{}^{}\mathrm{Ti}$, ${}_{}{}^{54}{}_{}{}^{}\mathrm{Cr}$, and ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}$ have been measured as a function of proton energy in the energy range 3.0-4.9, 2.2-5.2, and 2.0-5.1 MeV in 5 keV steps, respectively. No strong isobaric analog resonances were seen in the data. The fluctuations in the excitation functions were analyzed to extract ${〈\Gamma 〉}_{\mathrm{av}}$ values using the "counting of maxima" method. The excitation functions, averaged over 100 keV energy interval reveal prominent intermediate width structures in the case of ${}_{}{}^{50}{}_{}{}^{}\mathrm{Ti}$. All the three excitation functions were averaged over suitable energy intervals and compared with the total reaction cross sections calculated utilizing the optical model. The data on ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}$ and ${}_{}{}^{54}{}_{}{}^{}\mathrm{Cr}$ agreed, while the data on ${}_{}{}^{50}{}_{}{}^{}\mathrm{Ti}$ indicated a marked discrepancy with these optical model calculations. In the latter case, detailed Hauser-Feshbach (HF) and Hauser-Feshbach-Moldauer (HFM) calculations were carried out. The HFM calculations fit the data quite well. The importance of $\sigma (p, n)$ measurements in determining the imaginary potential of the optical model at sub-Coulomb energies has been indicated.

NUCLEAR REACTIONS ${}_{}{}^{54}{}_{}{}^{}\mathrm{Cr}(p, n)$, $E=2.2-5.2\mathrm{}$ MeV; ${}_{}{}^{50}{}_{}{}^{}\mathrm{Ti}(p, n)$, $E=3.0-4.9\mathrm{}$ MeV; ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}(p, n)$, $E=2-5.1\mathrm{}$ MeV measured $\sigma \mathrm{}\left(E\right)\mathrm{}$; extracted ${〈\Gamma 〉}_{\mathrm{av}}$; optical model and Hauser-Feshbach analyses.

• Received 12 May 1975

DOI:https://doi.org/10.1103/PhysRevC.12.1789