Revisiting the decay scheme and half-life of ¹³⁹Ba

Abstract

The decay of ¹³⁹Ba to levels of ¹³⁹La has been studied employing singles and $\gamma$ -$\gamma$ coincidence spectroscopy techniques, using four Compton suppressed Clover detectors. The $\gamma$ -$\gamma$ coincidence data obtained in the present work has been more conclusive as compared to the coincidence data obtained using NaI(Tl)-Ge(Li) detectors in the earlier investigations. The relative intensities of twenty-seven $\gamma$ -ray transitions have been determined. The $\gamma$ -ray transitions with energies 1044 and 1525keV, attributed to the decay of ¹³⁹Ba in the previous works, have been found to be due to long-lived impurities. The 1691keV transition, previously assigned to the decay of ¹³⁹Ba , is found to be mainly associated with an impurity with only a small fraction belonging to ¹³⁹Ba decay. The half-life of ¹³⁹Ba has been measured. The present work attempts to resolve some of the discrepancies in the previous investigations, which will be helpful in the precise determination of $\beta$ -decay scheme of ¹³⁹Ba.