We investigate reaction mechanisms occurring in heavy ion collisions at low
energy (around 20 MeV/u). In particular, we focus on the competition between
fusion and break-up processes (Deep-Inelastic and fragmentation) in
semi-peripheral collisions, where the formation of excited systems in various
conditions of shape and angular momentum is observed. Adopting a Langevin
treatment for the dynamical evolution of the system configuration, described in
terms of shape observables such as quadrupole and octupole moments, we derive
fusion/fission probabilities, from which one can finally evaluate the
corresponding fusion and break-up cross sections. The dependence of the results
on shape, angular momentum and excitation energy is discussed.Comment: submitted to Physical Review