Spectroscopy of the light rare-Earth nuclei 133Pm and 133Sm

Abstract The low-lying, rotational band structures of the highly neutron-deficient light rare-earth nuclei, 133Sm and 133Pm have been investigated using the 40Ca + 96Ru reaction at a beam energy of approximately 180 MeV. Five new bands have been observed in both nuclei. 133Sm possesss two strongly coupled bands which are thought to be built upon the v h 11 2 [523] 7 2 − and v d 5 2 [402] 5 2 + Nilsson configurations. In addition to the previously reported v i 13 2 intruder band, there is also evidence for a second decoupled, negative-parity structure in 133Sm based on the v h 9 2 [541] 1 2 − orbital. In 133Pm evidence is presented for both signature partners of the π h 11 2 band. The expected h 11 2 neutron alignment in these bands has not been observed. It is suggested that this provides evidence for a strong pn interaction. A strongly coupled band built on the π g 7 2 [413] 5 2 + configuration has also been established. Both signature partners of this band show clear evidence for the alignment of a pair of h 11 2 protons followed by a pair of h 11 2 neutrons. A strongly coupled three quasi-particle configuration has also been identified which feeds into the unfavoured signature of the π h 11 2 band. The results are discussed in terms of cranked shell model, total routhian surface calculations and the systematics of the A ∼ 135 region.