Precise measurement of the β decay and electron capture ofNa22,Au198

Abstract

We investigated half-life changes with temperature of 22 Na embedded in Al and 198 Au/ 196 Au 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 22 Na, 0.03% for 198 Au, and 0.5% for 196 Au in striking disagreement with the first experimental works and predictions. Additionally, the absolute half-life for 198 Au 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.

Half-life ofFr221in Si and Au at 4 K and at millikelvin temperatures

“…Because of the findings reported in [16] and [17], it comes as no surprise that our results do not support the Debye-Hücker model [1][2][3], which predicts (based on the calculations of [11,12]) a reduction of the half-life of 221 Fr in a metal at 4 K with a factor of about 50, and at 20 mK with a factor of many orders of magnitude more. No dependency on the solid-state environment and temperature of this α decaying isotope is observed up to a level of 1 × 10 −3 , which is at variance with the reported 6% change of the activity of 213 Po nuclei implanted in Cu at 12 K [4].…”

“…Note that electron capture decay rates may depend on the material hosting the radioactive isotope via small modifications of the electron density around the EC-decaying nucleus (see, e.g., [8] and references therein). In contrast to the above results, several experiments carried out at a later stage on the β-decaying isotopes 198 Au [9][10][11][12], 22 Na [11,12], 64 Cu [13], and 74 As [14], and on the EC-decaying 7 Be [10], did not observe any changes of the half-lives up to the permille level when these isotopes were embedded in a metallic environment and cooled down to 10-20 K.…”

“…These dedicated half-life measurements bring down the level to which no temperature and host-material effect is observed on nuclear half-lives for α decays to the same level of precision as was already established for β decays and EC decays in Refs. [8][9][10][11][12][13][14].…”

The 198Au β − half-life in the metal Au revisited

“…In summary we confirm the conclusion of recent works [2,3,4,5] that no temperature effect on the half-life of 198 Au is present within the statistical uncertainties of this experiment. Table 1.…”

“…In a recent experiment an increase in the half-life T 1/2 for the β − -decay of 198 Au from 2.706 ± 0.019 d to 2.802 ± 0.020 d has been observed cooling the sample to T = 12 K [1]. This observation triggered a number of half-life measurements on various isotopes, which could not confirm the results [2,3,4,5,6,7].…”