Towards a precise measurement of ¹⁵⁷Tb nuclear decay data: Sample purification using resonance ionization mass spectrometry

Abstract In nuclear physics, 157 Tb emerges as a prime candidate for experiments aimed at elucidating neutrino mass constraints and at searching for sterile neutrinos. Despite its importance, 157 Tb exhibits highly uncertain values for its nuclear decay properties. A significant challenge in many efforts to measure such data lies in the simultaneous undesired presence of 158 Tb in the samples, which hinders precise activity determination. Mass separation emerges as a crucial method for obtaining pure 157 Tb specimens. This work outlines the production of an isotopically-pure 157 Tb sample through mass separation and ion implantation, using the RISIKO facility at the University of Mainz. The initial material was obtained from proton-irradiated Ta samples through radiochemical separation at the Paul Scherrer Institute. In total, a sample containing 8.7(9) · 10 12 atoms of 157 Tb was obtained. The efficiency of the mass separation and ion implantation was 13(2) %. The purified material served as the basis for new research endeavors at the Physikalisch Technische Bundesanstalt Braunschweig aiming at the determination of nuclear data for 157 Tb with significantly improved precision.