Evolution of nuclear structure in O(6)-like nuclei

The evolution of nuclear structure along the Xe and Ba isotopes with N{lt}82 is studied in comparison with that in the Pt-Os isotopes and with interacting boson approximation calculations. As is well known, the Pt isotopes from {sup 188{minus}196}Pt exhibit a stable structure very close to O(6), the lighter Pt isotopes and the Os nuclei evolve towards a rotor, and the heaviest Pt nuclei, {sup 198,200}Pt, show a tendency towards vibrational character. In contrast, we show that the Ba nuclei are best described by a trajectory from U(5) towards SU(3) that passes through an intermediate structure that resembles O(6) for N{approximately}72{endash}76. The Xe appears to evolve from U(5) to O(6)-like. {copyright} {ital 1998} {ital The American Physical Society}