The existence of zinc radioactivities with half-lives 57 minutes and 13.8 hours is confirmed, by deuteron activation of zinc. In addition, it is found that both these activities are produced by deuteron and by fast neutron irradiation of gallium, so that the two periods must be due to isomers of ${\mathrm{Zn}}^{69}$. Both emit negative electrons and the properties of their radiations are given. It is shown that ${\mathrm{Zn}}^{65}$, produced through deuteron bombardment of zinc, has a half-life of 250 days, agreeing with the period found by others after proton and deuteron bombardment of copper. This isotope appears to decay by $K$ electron capture and also, to a lesser extent, by positron emission. No evidence has been found for radioactive ${\mathrm{Zn}}^{71}$. All previously reported zinc activities are discussed and the following table contains all the known periods that are believed to be genuine.

• Received 15 December 1938

DOI:https://doi.org/10.1103/PhysRev.55.457