  The isoscaling is investigated using the fragment yield data from fully
reconstructed quasi-projectiles observed in peripheral collisions of 28Si with
124,112Sn at projectile energies 30 and 50 MeV/nucleon. The excitation energy
dependence of the isoscaling parameter beta_prime is observed which is
independent of beam energy. For a given quasi-projectile produced in reactions
with different targets no isoscaling is observed. The isoscaling thus reflects
the level of N/Z-equilibration in reactions with different targets represented
by the initial quasi-projectile samples. The excitation energy dependence of
the isoscaling parameter beta_prime, corrected for the trivial 1/T temperature
dependence, does not follow the trend of the homogeneous system above 4
MeV/nucleon thus possibly signaling the onset of separation into isospin
asymmetric dilute and isospin symmetric dense phase.
