  An investigation of the quasiprojectile breakup channel in semiperipheral and
peripheral collisions of $^{58,64}$Ni+$^{58,64}$Ni at 32 and 52 MeV/nucleon is
presented. Data have been acquired in the first experimental campaign of the
INDRA-FAZIA apparatus in GANIL. The effect of isospin diffusion between
projectile and target in the two asymmetric reactions has been highlighted by
means of the isospin transport ratio technique, exploiting the
neutron-to-proton ratio of the quasiprojectile reconstructed from the two
breakup fragments. We found evidence that, for the same reaction centrality, a
higher degree of relaxation of the initial isospin imbalance is achieved in the
breakup channel with respect to the more populated binary output, possibly
indicating the indirect selection of specific dynamical features. We have
proposed an interpretation based on different average projectile-target contact
times related to the two exit channels under investigation, with a longer
interaction for the breakup channel. The time information has been extracted
from AMD simulations of the studied systems coupled to GEMINI++: the model
calculations support the hypothesis hereby presented.
