Half-Lives and Neutron Capture Cross Sections of the Heavy Plutonium Isotopes

Specific alpha activities have been obtained for ${\mathrm{Pu}}^{240}$ and ${\mathrm{Pu}}^{242}$ corresponding to half-lives of 6600±100 years and 379 000±5000 years, respectively. A half-life of (7.5±2)×${10}^7$ years has been obtained for ${\mathrm{Pu}}^{244}$ by separating uranium daughters. The irradiation of a sample of Pu containing ${\mathrm{Pu}}^{244}$ gave a neutron capture cross section of 2.1±0.3 barns for ${\mathrm{Pu}}^{244}$ and yeilded 10.6±0.4 hr ${\mathrm{Pu}}^{245}$ and its 124±1 min ${\mathrm{Am}}^{245}$ daughter.