Decay ofCe143

Abstract

The decay of 33-h ${\mathrm{Ce}}^{143}$ has been investigated using scintillation and coincidence spectrometers. The analysis of the singles $\gamma$-ray spectrum showed 36- (x ray), 57-, 142-, 232-, 293-, 351-, 450-, 493-, 591-, 668-, 725-, 810-, 885-, 942-, 1045-, 1100-, and 1340-keV $\gamma$ rays. All the $\gamma$ rays except the 142-keV $\gamma$ ray were found to follow a half-life of 33 h. The 142-keV $\gamma$ ray, which was thought to be entirely due to ${\mathrm{Ce}}^{141}$, has also been shown to be present in ${\mathrm{Ce}}^{143}$ by $\gamma -\gamma$ coincidences. The 1340-keV $\gamma$ ray was newly observed in this investigation. Extensive $\gamma -\gamma$ coincidences showed the presence of previously unreported weak transitions of energy 220, 374, 436, 449, 453, 810, and 1045 keV. The level at 493 keV has been established, and evidence for a new level at 1395 keV has been obtained. A revised decay scheme consistent with these observations and the previous $\beta$-ray measurements has been presented with excited states in ${\mathrm{Pr}}^{143}$ at 57, 351, 493, 725, 942, 1160, and 1395 keV.