Half-life of the nuclear cosmochronometer $^{176}$Lu measured with a windowless 4π solid angle scintillation detector

The 176Lu-176Hf nuclear decay is a powerful tool to measure the age of astrophysical and geological events and has been used as a “cosmochronometer”. However, the half-life values of 176Lu measured with various experiments differ significantly. Furthermore, the half-life values evaluated from Lu-Hf isochrons in meteorites and terrestrial rocks with known ages show two different values. Here we report half-life measurements using a method that is almost independent of various uncertainties. To the best of our knowledge this is the most accurate value of 176Lu half-life. We measure the total energy released from 176Lu decay using a windowless 4π solid angle detector based upon bismuth germanate (BGO) scintillation crystals, where a natural Lu sample is located inside of the detector. The measured half-life of (3.719 ± 0.007) × 10^10 yr corresponding to a decay constant of (1.864 ± 0.003) × 10^−11 yr−1 is consistent with that obtained from the analysis of terrestrial rocks within the uncertainty.

Takehito Hayakawa, Toshiyuki Shizuma, Tsuyoshi Iizuka