Half-life of samarium-147

The alpha-decay half-life of 147Sm has been reevaluated. Known amounts of natural Sm and an alpha-emitter standard (210Po, 238U, or 241Am) were mixed well to prepare thin sources for the simultaneous counting of 147Sm and the alpha-emitter standard by means of an alpha-spectrometer using a silicon surface barrier detector. The alpha-disintegration rate of known amounts of 147Sm was determined by reference to the alpha activity of the standard. The source preparation and counting were repeated to establish the reproducibility of the present half-life determination, and supplementary alpha spectrometry was carried out by a liquid-scintillation spectrometer. The arithmetic mean of the experimental half-life values was obtained to be (1.17 ± 0.02) x 1011 y. This value is about 10% longer than the currently adopted value, (1.06 ± 0.02) x 1011 y, and the possible factors for this difference are discussed. (author)