Radioisotopes of Osmium

Osmium activities of 15-day and 32-hour half-lives have been identified with ${\mathrm{Os}}^{191}$ and ${\mathrm{Os}}^{193}$, respectively. A 14-hour activity, decaying by a 74.2-kev gamma-transition into the 15-day activity, has been assigned to an isomeric state in ${\mathrm{Os}}^{191}$. The decay scheme of ${\mathrm{Os}}^{191}$ has been investigated and a 7/2+ assignment has been made to the 15-day ground state and an $i_{\frac{13}{2}}$ assignment to the 14-hour isomeric state. The 7/2+ state is attributed to a coupling of an odd number of ${\mathbf{i}}_{\frac{13}{2}}$ neutrons.