High Precision Half‑Life Measurement of the Extinct Radio‑Lanthanide Dysprosium-154

Abstract

Sixty years after the discovery of 154Dy, the half-life of this pure alpha-emitter was re-measured. 154Dy was radiochemically separated from proton-irradiated tantalum samples. Sector field- and multicollector-inductively coupled plasma mass spectrometry were used to determine the amount of 154Dy retrieved. The disintegration rate of the radio-lanthanide was measured by means of α-spectrometry. The half-life value was determined as (1.33 ± 0.07)∙106 y, with an uncertainty reduced by a factor of ~10 compared to the currently adopted value of (3.0 ± 1.5)∙106 y. This precise half-life value is crucial for the correct estimation of p-process nucleosynthetic reactions in the lanthanide region, as well as for the safe disposal of irradiated target material from spallation facilities. As a first application of the half-life value found in this work, the excitation functions for the production of 154Dy in proton-irradiated Ta, Pb, and W targets were re-evaluated, which found to be in agreement with theoretical calculations.