Determination of the half-life of gadolinium-148

The half-life of the alpha-emitter ¹⁴⁸Gd 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 ¹⁴⁸Gd were obtained by reprocessing proton-irradiated tantalum material. Multicollector-inductively coupled plasma mass spectrometry was performed to determine the amount of ¹⁴⁸Gd atoms retrieved. The activity of the ¹⁴⁸Gd atoms contained in the Gd sample was measured by means of alpha-spectrometry. The half-life of ¹⁴⁸Gd was deduced to be 86.9 years, with a combined uncertainty of 4.5%.