Measurement of the half-life of excited nuclear states using liquid scintillation counting

This work presents measurements of the half-lives of excited nuclear states of ²³⁷Np and ⁵⁷Fe using a liquid scintillation (LS) spectrometer and a gamma detector. A novel approach for the determination of the half-lives of some excited states is presented which uses only LS counting data from a detector with two PMTs. The lifetime of the 1st and 2nd excited states of ⁵⁷Fe were obtained without the use of a gamma detector. The obtained value for the 59.54 keV level of ²³⁷Np is 67.60(25) ns. The obtained values for the 14.4 keV and 136.5 keV levels of ⁵⁷Fe are 97.90(40) ns and 8.780(36) ns, respectively. The half-life results from this study are consistent with the average value found in the reference decay data tables and have a lower uncertainty.