Insights into the low energy incomplete fusion

In the present work, channel-by-channel excitation functions of different evaporation residues populated via complete and/or incomplete fusion in C12+169Tm system have been measured for an energy range Elab?53–90MeV, using recoil-catcher activation technique followed by off-line ?-spectroscopy. Experimentally measured excitation functions have been analysed in the framework of statistical model code PACE. To probe the effect of entrance-channel parameters on the onset and strength of incomplete fusion, relative contributions of complete and incomplete fusion have been deduced from the analysis of experimentally measured excitation functions. The percentage fraction of incomplete fusion deduced from the analysis of excitation functions has been studied in terms of incident energy, entrance-channel mass-asymmetry, ground state alpha-Q-value, neutron skin thickness of target nuclei, and nuclear potential parameters. It has been found that incomplete fusion start competing with complete fusion even at slightly above barrier energies where complete fusion is assumed to the sole contributor. The probability of incomplete fusion increases with incident energy, entrance channel mass-asymmetry, large negative ground state alpha-Q-value, neutron skin thickness, and nuclear potential parameters for individual projectiles.Indian Institute of Technology Bombay Science and Engineering Research Board Central Mechanical Engineering Research Institute, Council of Scientific and Industrial ResearchWe thank the Director of IUAC New Delhi for extending necessary facilities to perform these experiments, target laboratory for helping in the target preparations, and the Pelletron crew for smooth operation during the experiments. Authors are thankful to Prof. R. K. Bhowmik, Prof. P. K. Raina, Dr. S. Muralithar, Dr. R. P. Singh for scientific discussions during the experiments and data analysis. One of the authors P.P.S. acknowledges startup grant from the Indian Institute of Technology Ropar, the Council of Scientific and Industrial Research for a research grant ref.no. CSIR/03(1353)/16/EMR-II , and the Science and Engineering Research Board for a young scientist award ref.no. YSS/2014/000250

Fission-like events in the C 12 + Tm 169 system at low excitation energies

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 C12+Tm169 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 ? spectroscopy was used to measure production cross sections of fission-like events. The evaporation residues were identified by their characteristic ? 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 ? 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. © 2017 American Physical Society.Science and Engineering Research BoardWe thank the Director of IUAC New Delhi for providing all the necessary facilities to perform these experiments. P.P.S. thanks the Science and Engineering Research Board (SERB), India for Young Scientist Research Grant No. YSS/2014/000250, and S.A. acknowledges a research grant received from Aksaray University for Project No. 2016-053