SUCCESSIVE DECAYS FROM Pr137 AND Ce137m: DECAY OF ADJACENT PRASEODYMIUM ISOTOPES

Abstract

The decay of Pr137 entirely to a 9.0-hour ground state of Ce137 was independently discovered. By allowed electron capture, Ce137 decays predominantly to a low-lying state of La137, with only a 3% branching to a 440-kev excited state. The 440-kev transition is at least predominantly E2 in character.A 34.4-hour isomeric state produced by the La139(p, 3n)Ce137m reaction decays by a 254.5-kev M4 transition to the 9-hour -ground state. A 0.6% branching was found from the isomeric state directly to a small group of apparently high spin states in La137.Studies of mass-separated isotopes confirmed the existence of 1.5-hour Pr137 and 1.0-hour Pr136. The K-capture to positron branching ratios observed in the decay of Pr139, Pr138, Pr137, and Pr136 show that these isotopes decay by allowed transitions to their cerium daughters. Characteristic gamma rays were observed.