Spontaneous Fission Half-Life ofPu240

The spontaneous fission half-life of ${\mathrm{Pu}}^{240}$ has been measured, using ionization chamber and coincidence techniques, on sources containing microgram quantities of plutonium with 91.89 weight percent ${\mathrm{Pu}}^{240}$. A new value of (1.340±0.015)×${10}^{11}$ years was obtained, which is higher than the previously accepted value.