  The fission-fragments mass-yield of 236U is obtained by an approximate
solution of the eigenvalue problem of the collective Hamiltonian that describes
the dynamics of the fission process whose degrees of freedom are: the fission
(elongation), the neck and the mass-asymmetry mode. The macroscopic-microscopic
method is used to evaluate the potential energy surface. The macroscopic energy
part is calculated using the liquid drop model and the microscopic corrections
are obtained using the Woods-Saxon single-particle levels. The four dimensional
modified Cassini ovals shape parametrization is used to describe the shape of
the fissioning nucleus. The mass tensor is taken within the cranking-type
approximation. The final fragment mass distribution is obtained by weighting
the adiabatic density distribution in the collective space with the
neck-dependent fission probability. The neck degree of freedom is found to play
a significant role in determining that final fragment mass distribution.
