Cross sections for the production of ${}_{}{}^{18}{}_{}{}^{}\mathrm{F}$, ${}_{}{}^{22}{}_{}{}^{}\mathrm{Na}$, and ${}_{}{}^{24}{}_{}{}^{}\mathrm{Na}$ have been determined from the separated isotopes of magnesium, silicon, and sulfur, using 300- and 400-MeV protons. These values, together with previous measurements, provide data for targets of each mass number of 23 to 34 inclusive for ${}_{}{}^{18}{}_{}{}^{}\mathrm{F}$ and ${}_{}{}^{22}{}_{}{}^{}\mathrm{Na}$ and from 25 to 34 inclusive for ${}_{}{}^{24}{}_{}{}^{}\mathrm{Na}$. The main feature of the results is that the cross section is highest for those targets having the $\frac{N}{Z}$ closest to that of the products. Thus, events involving the loss of about the same number of neutrons as protons have the highest probability. Cascade-evaporation calculations were performed for 400-MeV protons on each of these nuclides. The calculations reproduce the experimental trends.

• Received 19 May 1969

DOI:https://doi.org/10.1103/PhysRevC.1.193