Fission barriers, coupled-channel, and shell effects at the Coulomb barrier in the A ∼ 190 mass region

A study of the role of coupled-channel effects in the enhancement of the population of high-spin states was undertaken with the reactions ⁴⁸Ca+¹⁴²Nd and ⁸⁰Se+¹¹⁰Pd, near the Coulomb barrier, leading to the same compound nucleus, ¹⁹⁰Hg, at the same excitation energy. Statistical calculations with standard values for the level density parameters and fission barriers predict an enhancement of the high-spin population for the more mass-symmetric system, brought about by the coupling to inelastic channels in the fusion process. No enhancement was observed which we interpret as an inadequacy of the fission barriers used, and to the role of the shell corrections, in particular those at the saddle point.