Change over from compound nuclear fission to quasi fission

Quasi-fission is a fission like process, which precedes the formation of a compact mono
nuclear system and thus a serious competitor for the formation of a compound nucleus. It
is a prominent reaction channel at low excitation energies, just above the the fusion
threshold, where the evaporation residue formation also maximizes. Therefore, for a
proper choice of target and projectile in a reaction aiming at the synthesis of a superheavy
element, it is important to study the quasi-fission reaction mechanism at beam
energies close to the Coulomb barrier for different target - projectile combinations of
varying entrance channel mass asymmetry which lead to the same fused system. It is
argued that there may be two factors that determine the quasi-fission reaction: (i) nuclear
orientation dependence, particularly for deformed target and/or projectile and (ii)
direction of mass flow towards increased mass symmetry. Our new measurements
show the clear evidence of importance of the effect of mass flow over that of the
dependence on the relative nuclear orientation, for different deformed target and
projectile combinations.