Structure of N=81 nuclei: Levels of Nd141 and Ce139 populated in beta decay
The nuclear level structure of Nd141 and Ce139 has been investigated by studying the decay of 20.9-min Pm141 produced via the Pr141(He3,3 n) reaction and the decay of 4.5-h Pr139 produced by the Pr140(, n)Pr139 reaction. For the Pm141 decay, singles and anti-Compton -ray spectra and - coincidence measurements were used to deduce a decay scheme that includes nine previously unreported levels in Nd141 and incorporates 67 of the 70 rays attributed to the decay of Pm141. Singles and anti-Compton spectra were taken as a function of time in order to confirm assignment of the Pr139 rays. The level structures of Nd141 and Ce139 are compared to recent measurements in other N=81 isotones. The results of this work are in good agreement with theoretical predictions based on the hole-vibrational coupling model for levels below 1.3 MeV. There exist more levels between 1.3 and 2.0 MeV than are predicted by this model, but these excess levels can be explained qualitatively within a weak coupling framework. RADIOACTIVITY Pm141 [from Pr141(He3, 3n)] and Pr139 [from Pr140(, n)] measured E, I, - coin; deduced Nd141 and Ce139 levels, J, , and logft values. Natural target, Ge(Li) detectors, anti-Compton spectrometer. © 1976 The American Physical Society.
Zalutsky, MR; MacIas, ES; Meyer, RA
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