The identification and characteristics of several beta-emitting nuclides are reported. The half-life of ${\mathrm{W}}^{188}$ is 65 days, ${\mathrm{Os}}^{194}$ about 700 days, while ${\mathrm{Re}}^{189}$ might be either of two isotopes having half-lives of about 150 days or of at least five years. The mass assignment of ${\mathrm{W}}^{181}$ has been confirmed in view of its presence in thermal-neutron irradiated tungsten. ${\mathrm{Re}}^{188}$ was found to have a half-life of 16.9 hours. No gamma-radiation could be found by absorption measurements to be associated with the 18-hour ${\mathrm{Ir}}^{194}$ daughter of ${\mathrm{Os}}^{194}$. Thermal-neutron activation cross sections are reported for most of the nuclides.

• Received 2 July 1951

DOI:https://doi.org/10.1103/PhysRev.84.240