Mass-asymmetric fission in the ⁴⁰ca+¹⁴²Nd reaction

¹ Department of Nuclear Physics, Research School of Physics and Engineering, Australian National University, Canberra, ACT 2601, Australia
² GSI Helmholtzzentrum fur Schwerionenforschung, 64291, Darmstadt, Germany

^a e-mail: prasad.edayillam@anu.edu.au
^b Permanent Address: Department of Physics, Central University of Kerala, Kasaragod, 671314, India.
^c Presently at National Superconducting Cyclotron Laboratory, Michigan State University, Michigan, 48824, USA.
^d Presently at Bhabha Atomic Research Center, Mumbai 400085, India.
^e Helmholtz Institute Mainz, 55099 Mainz, Germany.
^f Institute for Nuclear Chemistry, Johannes Gutenberg University Mainz, 55128 Mainz, Germany.

Published online: 5 September 2016

Abstract

Shell effects play a major role in fission. Mass-asymmetric fission observed in the spontaneous and low energy fission of actinide nuclei was explained by incorporating the fragment shell properties in liquid drop model. Asymmetric fission has also been observed in the low energy fission of neutron-deficient ¹⁸⁰Hg nuclei in recent β-delayed fission experiments. This low-energy β-delayed fission has been explained in terms of strong shell effects in pre-scission configurations associated with the system after capture. Calculations predicted asymmetric fission for heavier Hg isotopes as well, at compound nuclear excitation energy as high as 40 MeV. To explore the evolution of fission fragment mass distribution as a function of neutron and proton numbers and also with excitation energy, fission fragment mass distributions have been measured for the ⁴⁰Ca+¹⁴²Nd reaction forming the compound nucleus ¹⁸²Hg at energies around the capture barrier, using the Heavy Ion Accelerator Facility and CUBE spectrometer at the Australian National University. Mass-asymmetric fission is observed in this reaction at an excitation energy of 33.6 MeV. The results are consistent with the β-delayed fission measurements and indicate the presence of shell effects even at higher exciation energies.