Determination of the half-life of gadolinium-148.

The half-life of the alpha-emitter Gd was measured using the "direct method", in which the number of atoms is directly determined and their activity is then measured. Pure Gd samples containing megabecquerels of Gd were obtained by reprocessing proton-irradiated tantalum material. Multicollector-inductively coupled plasma mass spectrometry was performed to determine the amount of Gd atoms retrieved. The activity of the Gd atoms contained in the Gd sample was measured by means of alpha-spectrometry. The half-life of Gd was deduced to be 86.9 years, with a combined uncertainty of 4.5%.