We perform coincidence measurements between α particles and γ rays from a U233 source to determine the half-lives of the excited state in a Th229 nucleus. We first prove that the half-lives of 42.43- and 164.53-keV states are consistent with literature values, whereas that of the 97.14-keV state [93(7) ps] deviates from a previously measured value [147(12) ps]. The half-lives of 71.83- and 163.25-keV states are determined for the first time. Based on the obtained half-lives and the Alaga rule, we estimate the radiative half-life of the low-energy isomeric state (Th229m) to be 5.0(11)×103 s, which is one of the key parameters for the frequency standard based on Th229.
ASJC Scopus subject areas
- Nuclear and High Energy Physics