${\mathrm{Ni}}^{56}$ has been produced by the bombardment of the separated isotope ${\mathrm{Fe}}^{54}$ with 39-Mev alpha-particles. It is a 6.4±0.1 day orbital electron capture activity with less than 1 percent positrons. Growth of its daughter ${\mathrm{Co}}^{56}$ makes the mass assignment certain and confirms the 6.4-day half-life. Gamma-rays of the following energies in Mev (and relative intensities) have been found: 0.17 (1.0), 0.28 (0.3), 0.48 (0.4), 0.81 (0.8), 0.96 (0.1), 1.33 (0.05), 1.58 (0.15), and 1.75 (0.02). The half-lives of most of these gamma-rays have been followed individually and agree with the half-life quoted. The large number of gammas indicates that the decay scheme is complex. Coincidences have been found between the cobalt $K$ x-rays and the gammas as well as between the gamma-rays themselves. There is less than ${10}^{-4\mathrm{}}$ alpha-branching.

• Received 31 March 1952

DOI:https://doi.org/10.1103/PhysRev.87.1