The ${}_{}{}^{238}{}_{}{}^{}\mathrm{Pu}$ half-life was measured at 87.71 ± 0.03 yr by observing the ${}_{}{}^{238}{}_{}{}^{}\mathrm{Pu}$ $\alpha$-particle activity formed from the $\alpha$ decay of ${}_{}{}^{242}{}_{}{}^{}\mathrm{Cm}$. Samples of ${}_{}{}^{242}{}_{}{}^{}\mathrm{Cm}$ were counted three times in a 262 day interval, leading to a ${}_{}{}^{242}{}_{}{}^{}\mathrm{Cm}$ half-life of 162.76 ± 0.04 days. Both values agree well with measurements made by other methods.

RADIOACTIVITY ${}_{}{}^{238}{}_{}{}^{}\mathrm{Pu}$; measured $T_{\frac{1}{2}}$, precise gravimetric aliquots, high precision $\alpha$ counting, ${}_{}{}^{242}{}_{}{}^{}\mathrm{Cm}$; measured $T_{\frac{1}{2}}$.

• Received 8 November 1976

DOI:https://doi.org/10.1103/PhysRevC.15.1034