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 Cu⁶², Cu⁶¹ and Cu⁶⁴, respectively. The reactions are principally of the p-n type but there is evidence that in the case of Cu⁶² proton capture occurs at energies below the p-n threshold. The maximum β-ray energies obtained by absorption method are 2.8, 1.2 and 0.68 Mev for Cu⁶², Cu⁶¹ and Cu⁶⁴, 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 Zn⁶³ and Zn⁶⁵, respectively. Both must be formed by p-n reactions. The Zn⁶³ 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 Cu⁶³(p-n)Zn⁶³ reaction is 0.28×{}10^-25 cm². For protons of energy 6.1 Mev it is 0.95×{}10^-25 cm.