End-point energy and half-life of the ¹⁸⁷Re β decay

A high statistics measurement of the β decay of ¹⁸⁷Re with a cryogenic microcalorimeter has been performed. The high accuracy and the calorimetric nature of the measurement allow setting a value for the end-point energy of the decay in a metallic rhenium crystal equal to [2470± 1 (stat)±4(syst)] eV. A good extrapolation of the spectrum to zero energy has also been possible thanks to the stable and well determined detector response down to the energy threshold of about 420 eV. This allows an estimate of the ¹⁸⁷Re half-life of [4.12±0.02(stat)±0.11(syst)]× 10¹⁰ yr. Both results are significantly better than the previous measurements reported in the literature.