  We extend a recent study that explained the steep falloff in the fusion cross
section at energies far below the Coulomb barrier for the symmetric dinuclear
system 64Ni+64Ni to another symmetric system, 58Ni+58Ni, and the asymmetric
system 64Ni+100Mo. In this scheme the very sensitive dependence of the internal
part of the nuclear potential on the nuclear equation of state determines a
reduction of the classically allowed region for overlapping configurations and
consequently a decrease in the fusion cross sections at bombarding energies far
below the barrier. Within the coupled-channels method, including couplings to
the low-lying 2+ and 3- states in both target and projectile as well as mutual
and two-phonon excitations of these states, we calculate and compare with the
experimental fusion cross sections, S-factors, and logarithmic derivatives for
the above mentioned systems and find good agreement with the data even at the
lowest energies. We predict, in particular, a distinct double peaking in the
S-factor for the far subbarrier fusion of 58Ni+58Ni which should be tested
experimentally.

Nuclear Theory