Precision measurement of the half-lifes of the excited nuclear states in Fe-57

Abstract

The half-lifes of the nuclear isomeric states in ⁵⁷Fe at 14.4 keV and 136.5 keV above the ground state are measured with unprecedented precision using hybrid pixel detectors based on Timepix3 technology. These detectors enable dead-time-free single-photon detection and provide simultaneous measurements of photon energy and arrival time, allowing for nanosecond-scale determination of time differences between characteristic X-rays and \(\gamma \)-rays emitted during the electron-capture decay of ⁵⁷Co. Employing the delayed coincidence technique, the half-life of the 14.4-keV state is determined as \(t^{14.4 \text { keV}}_{1/2} = 97.82(5)\) ns, achieving a fourfold improvement in precision over previous measurements. The half-life of the 136.5-keV state is measured as \(t^{136 \text { keV}}_{1/2}= 8.730(17)\) ns, reducing the uncertainty by a factor of two. These results are discussed in the context of previous works.