  With a help of the selfconsistent Hartree-Fock-Bogoliubov (HFB) approach with
the D1S effective Gogny interaction and the Generator Coordinate Method (GCM)
we incorporate the transverse collective vibrations to the one-dimensional
model of the fission-barrier penetrability based on the traditional WKB method.
The average fission barrier corresponding to the least-energy path in the
two-dimensional potential energy landscape as function of quadrupole and
octupole degrees of freedom is modified by the influence of the transverse
collective vibrations along the nuclear path to fission. The set of transverse
vibrational states built in the fission valley corresponding to a successively
increasing nuclear elongation produces the new energy barrier which is compared
with the least-energy barrier. These collective states are given as the
eigensolutions of the GCM purely vibrational Hamiltonian. In addition, the
influence of the collective inertia on the fission properties is displayed, and
it turns out to be the decisive condition for the possible transitions between
different fission valleys.
