Noncompound fusion reactions at low bombarding energy

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Background: The involvement of noncompound nuclear reactions in light and medium-heavy compound nuclei is not fully understood. In this regime, breakup fusion is regarded as the predominant reaction mode among all noncompound nuclear processes and has not been much explored explicitly.Purpose: A systematic study of the compound nucleus fusion probability of various compound nuclei populated through different target-projectile systems is undertaken to investigate its dependence on various entrance channel parameters. The study provides better insight to determine the onset of noncompound nucleus fusion, due to which compound nucleus fusion probability reduces.Method: In the present investigations, excitation functions of evaporation residues of 40 reactions leading to the formation of the compound nucleus in the mass region $\ensuremath{\approx}$ 64--195 have been taken into account from the literature. The compound nucleus fusion probability of these systems was calculated as the ratio of the compound nucleus fusion to the total fusion cross sections.Results: Reduction in compound nucleus fusion probability was observed with an increase in parameters such as the projectile energy, the charge of the target, the total asymmetry, and the critical angular momentum of the different systems. Moreover, the $\ensuremath{\alpha}\ensuremath{-}Q$ value of the projectiles was found to affect and trigger the noncompound nuclear fusion processes more than other entrance channel parameters. It was also observed from the present analysis that the values of maximum angular momenta are slightly larger than the values of critical angular momenta as extracted from the measured cross sections for the studied systems.Conclusions: The present study reveals the presence of noncompound nuclear fusion reactions in light- and medium-mass compound nuclei. This is mainly because of the loss in the flux of the compound nuclear fusion reaction and the subsequent gain in the flux of the noncompound nuclear fusion reaction. The observations further show that these processes are significantly influenced by the $\ensuremath{\alpha}\ensuremath{-}Q$ value of the projectiles. These results indicate that noncompound nuclear fusion processes occur in peripheral collisions.

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