Half-lives of 238Pu and 242Cm

The ²³⁸Pu half-life was measured at 87.71 +/- 0.03 yr by observing the ²³⁸Pu α-particle activity formed from the α decay of ²⁴²Cm. Samples of ²⁴²Cm were counted three times in a 262 day interval, leading to a ²⁴²Cm half-life of 162.76 +/- 0.04 days. Both values agree well with measurements made by other methods. RADIOACTIVITY ²³⁸Pu; measured T₁₂, precise gravimetric aliquots, high precision α counting, ²⁴²Cm; measured T₁₂.