Sharp change over from compound nuclear fission to shape dependent quasi fission

TL;DR

This study investigates how slight differences in entrance channel mass asymmetry influence fission fragment mass distributions in nuclear reactions near the Coulomb barrier, revealing a sharp transition from compound nuclear fission to shape-dependent quasi-fission.

Contribution

It demonstrates the significant impact of entrance channel mass asymmetry and target deformation on fission fragment distributions near the Coulomb barrier.

Findings

Fission fragment mass distribution width varies drastically with entrance channel.

Entrance channel mass asymmetry sharply affects the fusion process.

Deformation of target nuclei influences fission outcomes.

Abstract

Fission fragment mass distribution has been measured from the decay of $^{246}$Bk nucleus populating via two entrance channels with slight difference in mass asymmetries but belonging on either side of the Businaro Gallone mass asymmetry parameter. Both the target nuclei were deformed. Near the Coulomb barrier, at similar excitation energies the width of the fission fragment mass distribution was found to be drastically different for the $^{14}$N + $^{232}$Th reaction compared to the $^{11}$B + $^{235}$U reaction. The entrance channel mass asymmetry was found to affect the fusion process sharply.