Precision half-life measurement of 140La with Ge-detector

Half-life is one of the fundamental properties of radioactive nuclei, and the precision required for its numerous applications in modern physics sometimes approaches the level of 10(-4)-10(-5). Most part of the T-1/2 measurements performed up to now was made with proportional chambers, and the results were sometimes hardly reproducible within the error limits, Using Ge-detectors for that purpose brought some significant advantages but electronic unit related effects and spectra analysis procedures still remain the sources of the errors influencing the accuracy of the T-1/2 attained. In this work, La-140 samples were obtained in the La-130(n, gamma)La-140 reaction, employing a microtron as a neutron source and the half-life measurements were performed with a HPGe-detector. Influencing factors such as photopeak and background shape, electronic circuitry dead time and deadtime variations during the measurements, as well as pulse pileup are studied altogether. Values of the La-140 T-1/2 = 1.6808(18) d, lambda = 0.47749(20) x 10(-5), agreeing within the uncertainities with the most accurate evaluated ones (T-1/2 = 1.6781(3) d, lambda = 0.47807(9) x 10(-5)) [2] were obtained in two series of measurements. (C) 2002 Published by Elsevier Science B.V.