Proton Induced Radioactivities

Abstract

Results are tabulated of the radioactivities produced by 4 Mev protons in targets of ${}_7{}^{}{}_{}{}^{}\mathrm{N}$, ${}_8{}^{}{}_{}{}^{}\mathrm{O}$, ${}_{20}{}^{}{}_{}{}^{}\mathrm{Ca}$, ${}_{24}{}^{}{}_{}{}^{}\mathrm{Cr}$, ${}_{27}{}^{}{}_{}{}^{}\mathrm{Co}$, ${}_{30}{}^{}{}_{}{}^{}\mathrm{Zn}$, ${}_{34}{}^{}{}_{}{}^{}\mathrm{Se}$, ${}_{42}{}^{}{}_{}{}^{}\mathrm{Mo}$, ${}_{46}{}^{}{}_{}{}^{}\mathrm{Pd}$, ${}_{48}{}^{}{}_{}{}^{}\mathrm{Cd}$, ${}_{49}{}^{}{}_{}{}^{}\mathrm{In}$. In most cases the reactions are of the $p-n$ type, and lead to isotopes which emit either + or - electrons. A detailed study was made of O, Zn and Se. The reaction ${\mathrm{O}}^{18}(p, n){\mathrm{F}}^{18}$ (107 min.) shows a threshold at 2.56 Mev and a positron energy of 0.74 Mev in good agreement with the energy relations. The cross section for the reaction at 4 Mev is about 2×${10}^{-25\mathrm{}}$ ${\mathrm{cm}}^2$ and there is a resonance maximum at 3.55 Mev. The cross section for the reaction ${\mathrm{O}}^{16}(p, \gamma ){\mathrm{F}}^{17}$ is 4000 times smaller. The isomeric ${\mathrm{Br}}^{80}$ periods (17.4 min. and 4.45 hr.) are observed in the reaction ${\mathrm{Se}}^{80}(p, n){\mathrm{Br}}^{80}$. At 4 Mev the ratio of the short to long period activities for infinite bombardment is about 15 but the thresholds are at about 3.0 and 3.2 Mev, respectively. The cross section for the reaction is about 0.6×${10}^{-26\mathrm{}}$ ${\mathrm{cm}}^2$ at 4 Mev.