Study of (p, pn) Reactions in Medium Weight Nuclei at 370 MeV

Cross sections for the ($p, \mathrm{pn}$) reaction at a proton energy of 370 MeV have been measured with ${\mathrm{Sc}}^{45}$, ${\mathrm{Cr}}^{50}$, ${\mathrm{Cr}}^{52}$, ${\mathrm{Mn}}^{55}$, ${\mathrm{Fe}}^{56}$, ${\mathrm{Ni}}^{58}$, ${\mathrm{Co}}^{59}$, ${\mathrm{Cu}}^{65}$, ${\mathrm{Ga}}^{69}$, and ${\mathrm{Ga}}^{71}$ targets. All of the ($p, \mathrm{pn}$) cross sections, except those for ${\mathrm{Sc}}^{45}$, ${\mathrm{Cr}}^{50}$, and ${\mathrm{Ni}}^{58}$, were found to be about 60 mb. No quantitative explanation could be found for these three divergent cross sections, all of which are lower than the others. Cross sections for ($p, 2n$) reactions on ${\mathrm{Cr}}^{52}$ and ${\mathrm{Fe}}^{56}$ were also measured. Calculations based on the $(p, 2n)-(p, pn)$ ratio show that at least 85% of the ($p, \mathrm{pn}$) reactions proceed by a pure knock-on mechanism.