High precision half-life measurement of the extinct radio-lanthanide Dysprosium-154

Sixty years after the discovery of Dy-154, the half-life of this pure alpha-emitter was re-measured. Dy-154 was radiochemically separated from proton-irradiated tantalum samples. Sector field- and multicollector-inductively coupled plasma mass spectrometry were used to determine the amount of Dy-154 retrieved. The disintegration rate of the radio-lanthanide was measured by means of alpha-spectrometry. The half-life value was determined as (1.40 +/- 0.08).10(6) y, with an uncertainty reduced by a factor of similar to 10 compared to the currently adopted value of (3.0 +/- 1.5).10(6) y. This precise half-life value is useful for the the correct testing and evaluation of p-process nucleosynthetic models using Dy-154 as a seed nucleus or as a reaction product, as well as for the safe disposal of irradiated target material from accelerator driven facilities. As a first application of the half-life value determined in this work, the excitation functions for the production of Dy-154 in proton-irradiated Ta, Pb, and W targets were re-evaluated, which are now in agreement with theoretical calculations.