Precise measurement of the β decay and electron capture of Na22, Au198, and Au196 in low-temperature metal hosts, and reexamination of lifetime modifications

We investigated half-life changes with temperature of Na22 embedded in Al and Au198/Au196 embedded in Au. We do not find any change of the half-life between room temperature and 10 K on the level of 0.04% for Na22, 0.03% for Au198, and 0.5% for Au196 in striking disagreement with the first experimental works and predictions. Additionally, the absolute half-life for Au198 has been determined to 2.6937±0.0003 d which is 5 standard deviations below the recommended NIST value but in agreement with other high-precision measurements.