Abstract:
Background: Fission has been found to be a dominating mode of deexcitation in heavy-ion induced reactions
at high excitation energies. The phenomenon of heavy-ion induced fission has been extensively investigated
with highly fissile actinide nuclei, yet there is a dearth of comprehensive understanding of underlying dynamics,
particularly in the below actinide region and at low excitation energies.
Purpose: Prime objective of this work is to study different aspects of heavy-ion induced fission ensuing from the
evolution of composite system formed via complete and/or incomplete fusion in the 12C + 169Tm system at low
incident energies, i.e., Elab ≈ 6.4, 6.9, and 7.4 A MeV, as well as to understand charge and mass distributions of
fission fragments.
Method: The recoil-catcher activation technique followed by offline γ spectroscopy was used to measure
production cross sections of fission-like events. The evaporation residues were identified by their characteristic
γ rays and vetted by the decay-curve analysis. Charge and mass distributions of fission-like events were studied
to obtain dispersion parameters of fission fragments.
Results: In the present work, 26 fission-like events (32 Z 49) were identified at different excitation energies.
The mass distribution of fission fragments is found to be broad and symmetric, manifesting their production via
compound nuclear processes. The dispersion parameters of fission fragments obtained from the analysis of mass
and isotopic yield distributions are found to be in good accord with the reported values obtained for different
fissioning systems. A self-consistent approach was employed to determine the isobaric yield distribution.
Conclusions: The present work suggests that fission is one of the competing modes of deexcitation of complete
and/or incomplete fusion composites at low excitation energies, i.e., E∗ ≈ 57, 63, and 69 MeV, where evaporation
of light nuclear particle(s) and/or γ rays are assumed to be the sole contributors. A single peaked broad Gaussian
mass dispersion curve has corroborated the absence of any noncompound nuclear fission at the studied energies.