Intermediate mass fragment $\left(Z>2\right)$ emission in ${}^{124}\mathrm{Sn},{}^{124}\mathrm{Xe}+{}^{124}\mathrm{Sn},{}^{112}\mathrm{Sn}$ reactions at $28\text{MeV}∕\text{nucleon}$ were studied using neutron ion multidetector for reaction oriented dynamics, a $4\pi$ charged particle detection system. A number of observables, such as isotopic yield distributions, energy spectra of light charged particles and intermediate mass fragments, isotopic and isobaric yield ratios, and average neutron to proton ratios are investigated. These observables show significant dependence on the isospin $N∕Z$ of the reacting system. It is observed that the formation of neutron-rich clusters are correlated with the excess neutrons in the composite system and depends on the temperature of the emitting source. The origin of light particles and fragments was studied through observations of rapidity distribution as a function of collision violence. With increasing centrality, the heavier ${}^6\mathrm{He}$ isotope is found to be emitted closer to the midrapidity region than the lighter ${}^3\mathrm{He}$ isotope. The emission of heavy fragments from the midrapidity region becomes increasingly favorable for fragments with higher charge $Z$. The results suggest that the midrapidity region is not only neutron rich but also a rich source of heavy fragment (cluster) formation.

• Received 22 July 2003

DOI:https://doi.org/10.1103/PhysRevC.68.054605