Effect of shell structure on neutron multiplicity of fissioning systems ^220,222,224Th nuclei

¹ Department of Physics and Astrophysics, University of Delhi, Delhi, INDIA.
² Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi, INDIA.
³ CS-6/1, Golf Green, Kolkata. Formerly with Variable Energy Cyclotron Centre, Kolkata, INDIA.
⁴ Department of Physics, Panjab University, Chandigarh, INDIA.
⁵ Department of Physics, Kurukshetra University, Kurukshetra, INDIA.
⁶ Manipal Centre for Natural Sciences, Manipal University, Manipal, INDIA.
⁷ Saha Institute of Nuclear Physics, Kolkata, INDIA.
⁸ Amity Institute of Nuclear Science and Technology, Noida, INDIA.

^a Corresponding author: savi.november@gmail.com

Published online: 29 January 2015

Abstract

The pre- and post-scission neutron multiplicities have been extracted for the ^220,222,224Th nuclei for the excitation energy range of 40 MeV to 64 MeV using the National Array of Neutron Detectors (NAND). The Th isotopes are populated from the fusion reaction of ¹⁶O+^204,206,208Pb systems in order to investigate the dynamics of fusion-fission reactions using the neutron multiplicity as a probe. The theoretical calculations were performed using the Bohr-Wheeler fission width as well as the dissipative dynamical fission width from Kramers prescription. It is observed that the Bohr-Wheeler fission width underestimates the pre-scission yields to a large extent. A large amount of dissipation is required in the Kramers width to fit the observed pre-scission neutron multiplicities.