Fragments with atomic number 4$\le$Z$\le$28 have been studied from the reactions $^{78,82}$Kr + $^{40}$Ca at 5.5 AMeV incident energy by using the 4$\pi$-INDRA array at GANIL. Kinetic energy and angular distributions of fragments are compatible with an equilibrium statistical process. Results from the study of the average emission velocities and coincidence measurements between fragments show that binary-fission-like breakup of a completely fused nucleus, is the predominant mode of production for a large part of reaction products, and that the production mechanism is driven by Coulomb interaction. Absolute cross-sections were deduced by the normalization with respect to the elastic scattering. The cross-sections indicate the coexistence of macroscopic behavior and structural effects. For both reactions, a strong odd-even staggering is observed in the yields of asymmetric fission (5$\le$Z$\le$12) and the staggering is bigger for the neutron rich compound system. The symmetric fission yields is higher for the neutron rich $^{118}$Ba nucleus.

Analysis of the fragment-particle coincidence indicates that in asymmetric fission, the light partner is produced at excitation energy below the proton and alpha separation energy and consequently the secondary decays do not blur the properties of the primary splitting. Thus, the staggering in the yields may reflects the persistence of structure effects in strongly deformed system at the scission stage. This is qualitatively supported by the fact that the staggering of the yields seems to follow the staggering of the proton or alpha separation energies.

Experimental results are discussed in the framework of statistical and dynamical models.