Multiple band structures at high angular momentum inI115: Towards unfavored band termination

Six new rotational bands have been established in ${}_{}{}^{115}{}_{}{}^{}\mathrm{I}$ at high spin using the near symmetric ${}_{}{}^{60}{}_{}{}^{}\mathrm{Ni}$ ${(}^{58}$Ni,3pγ) reaction at 250 MeV. Several of the bands are observed to frequencies beyond ħω=1.0 MeV (spin approaching 50ħ). All the bands show a characteristic drop off in their dynamic moments of inertia with increasing spin. The low values at the highest spins are consistent with predictions for a band termination in which a gradual shape change from collective prolate to noncollective oblate occurs over many transitions. these smoothly occurring terminations contrast with the abrupt ‘‘favored’’ terminations previously observed in this and other odd-A iodine nuclei.