The Radioactive Isotopes of Nickel and Their Assignments

As a result of discrepancies in the reported methods of production and in the assignments of the radioactive isotopes of nickel the following reactions were investigated: $\mathrm{Fe}(\alpha ,n)$, $\mathrm{Co}\mathrm{}(d,2n)\mathrm{}$, $\mathrm{Ni}\mathrm{}(d,p)\mathrm{}$, $\mathrm{Ni}(n,\gamma )$, and $\mathrm{Ni}\mathrm{}(n,2n)\mathrm{}$. The relative yields of the known 2.6-hour and 36-hour periods from fast and slow neutrons on nickel were compared with other neutron reactions. The results obtained are in agreement with the assignment of the 2.6-hour period to ${\mathrm{Ni}}^{63}$ and the 36-hour period to ${\mathrm{Ni}}^{57}$. The possible existence of a short period in nickel, reported as a result of an $\mathrm{Fe}(\alpha ,n)$ reaction, is not established since it would be masked by the 2.1-minute oxygen period formed from the carbon present in iron. In the attempted separation of the ${\mathrm{O}}^{15}$ activity it was observed that under the prevailing experimental conditions the rate of removal of oxygen from bombarded iron approached the rate of decay of ${\mathrm{O}}^{15}$.