Half-life measurements of Rb by liquid scintillation counting

The specific activity of natural ⁸⁷Rb was measured by means of 4πβ liquid scintillation counting in a two-photomultiplier-tube spectrometer. ³H-efficiency tracing was used together with the CIEMAT/NIST method to obtain the detection efficiency. For this purpose a new parameterization of the shape factor for the third forbidden non-unique β-transition was performed. The hygroscopic behaviour of the salts used for sample preparation was studied. The half-life of ⁸⁷Rb was found to be T_1/2=4.967(32)×10¹⁰ y.