This work presents measurements of the half-lives of excited nuclear states of 237Np and 57Fe using a liquid scintillation 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 1^st^ and 2^nd^ 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.