  During the fission process, the nucleus deforms and elongates up to the two
fragments inception and their final separation at scission deformation. The
evolution of the nucleus energy with deformation is determined by the
macroscopic properties of the nucleus, and is also strongly influenced by the
single-particle structure of the nucleus. The fission fragment distribution is
a direct consequence of the deformation path the nucleus has encountered, and
therefore is the most genuine experimental observation of the potential energy
landscape of the deforming nucleus. Very asymmetric fusion-fission reactions at
energy close to the Coulomb barrier, produce well-defined conditions of the
compound nucleus formation, where processes such as quasi-fission,
pre-equilibrium emission and incomplete fusion are negligible. In the same
time, the excitation energy is sufficient to reduce significantly structural
effects, and mostly the macroscopic part of the potential is responsible for
the formation of the fission fragments. We use inverse kinematics combined with
spectrometers to select and identify the fission fragments produced in
$^{238}$U+$^{12}$C at a bombarding energy close to and well-above the Coulomb
barrier. For the first time, the isotopic yields are measured over the complete
atomic-number distribution, between Z=30 and Z=63. The experimental set-up also
allows to identify transfer-induced reactions, which lead to low-energy fission
where the nuclear shell structure shows a strong influence on the
fission-fragment distributions. The resulting set of data gives the possibility
to observe the fission fragment properties over a wide range of excitation
energy, and they reveal the vanishing of the shell effects in the potential
energy of the fissioning nucleus, as well as the influence of fission dynamics.
