Spectral shape and nuclear matrix elements in the β-decay of 206Tl

Abstract

The spectral shape, endpoint energy and half-life of the β-decay of 206Tl were measured. The β-particles were analysed in a 4π Si(Li) sandwich spectrometer. The sources used were isotopically separated and therefore extremely thin. The measured spectrum was corrected for the escape of bremsstrahlung. The extracted shape factor shows only small deviations from the statistical form, the endpoint energy of the decay is 1527 ± 4 keV, its half-life 4.27 ± 0.05 min. The nuclear matrix elements of this 0 − → 0 + decay have been calculated from single-particle wave functions. The resulting theoretical spectral form describes the experimental data very well, whereas the total transition probability is underestimated theoretically by a factor of 7.