Proton Induced Radioactivities II. Nickel and Copper Targets

Nickel bombarded with 6.3-Mev protons shows activities of half-lives of 10.5±0.6 min., 3.4±0.3 hr., and 12.8±0.8 hr., corresponding to known periods of ${\mathrm{Cu}}^{62}$, ${\mathrm{Cu}}^{61}$ and ${\mathrm{Cu}}^{64}$, respectively. The reactions are principally of the $p-n$ type but there is evidence that in the case of ${\mathrm{Cu}}^{62}$ proton capture occurs at energies below the $p-n$ threshold. The maximum $\beta$-ray energies obtained by absorption method are 2.8, 1.2 and 0.68 Mev for ${\mathrm{Cu}}^{62}$, ${\mathrm{Cu}}^{61}$ and ${\mathrm{Cu}}^{64}$, respectively. Thick target excitation curves are given. Copper bombarded with 6.3-Mev protons shows two activities of half-lives 38.3±0.5 min. and 235±20 days due to ${\mathrm{Zn}}^{63}$ and ${\mathrm{Zn}}^{65}$, respectively. Both must be formed by $p-n$ reactions. The ${\mathrm{Zn}}^{63}$ positrons have a maximum energy of 2.3±0.15 Mev. Thick target excitation curve shows a threshold proton energy of 4.1±0.1 Mev in good agreement with the energy relations. Average (thick target) cross section for the ${\mathrm{Cu}}^{63}\mathrm{}(p-n)\mathrm{}{\mathrm{Zn}}^{63}$ reaction is 0.28×${10}^{-25\mathrm{}}$ ${\mathrm{cm}}^2$. For protons of energy 6.1 Mev it is 0.95×${10}^{-25\mathrm{}}$ cm.