The new isotope ${\mathrm{Re}}^{189}$ has been produced by fast-neutron irradiation of osmium and by the ($\alpha , p$) reaction on tungsten. The rhenium was separated chemically from the target material. Beta-ray, gamma-ray, and internal conversion spectra have been measured. The mass assignment is confirmed by the observation of eleven electromagnetic transitions in the ${\mathrm{Os}}^{189}$ daughter, including the 30.8-keV isomeric transition (6h), all of which were known from the decay of ${\mathrm{Ir}}^{189}$. Rhenium-189 has a half-life of 23.4±1.0 h and emits beta-ray groups with end-point energies 1000, 780, and 725 keV, and probably others. Results of coincidence measurements lead to some new information about the level scheme of ${\mathrm{Os}}^{189}$. The effects of the expected rotation-particle coupling between low-lying $K=\frac{1}{2}$ and $K=\frac{3}{2}$ bands in ${\mathrm{Os}}^{189}$ are discussed.

• Received 3 April 1963

DOI:https://doi.org/10.1103/PhysRev.132.1681