Decay ofHf183and the Nuclear Spectroscopy ofTa183

The decay of ${\mathrm{Hf}}^{183}$ is studied after bombarding tungsten with 14-MeV neutrons, separating the Hf fraction by radiochemistry and using standard scintillation-counter techniques. The beta measurements show three beta groups of energies 2.21, 1.87, and 1.35 MeV. The first two groups decay with a half-life of 91 days and the last one decays with a half-life of 64 min. The gamma measurements show eight gamma rays of energies 95, 250, 345, 405, 500, 590, 750, and 930 keV. The 95-, 250-, and 340-keV gamma-rays are found to decay with half-lives of 64 min and 91 days; and the 345-, 405-, and 750-keV gamma rays decay with a half-life of 64 min only. A metastable state of ${\mathrm{Hf}}^{183}$ decays with a half-life of about 91 days; the ground state of ${\mathrm{Hf}}^{183}$ is found to decay with a half-life of 64 min. An electron conversion line of energy 640 keV is observed to decay with a half-life of 91 days only. The $\gamma -\gamma$ and $\beta -\gamma$ coincidences and the sum-coincidence studies have been performed, and based on these results a decay scheme of ${\mathrm{Hf}}^{183}$ and ${\mathrm{Hf}}^{183m}$ is proposed and results discussed.