Fission fragment mass and angular distribution in ^6,7Li+^235,238U reactions

¹ Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai - 400085, India
² Department of Physics, The M. S. University of Baroda, Vadodara - 390002, India
³ Department of Physics, Panjab University, Chandigarh - 160014, India
⁴ Radio Chemistry Division, Bhabha Atomic Research Centre, Mumbai - 400085, India
⁵ Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi - 110067, India
⁶ Department of Physics, Central University of Kerala, Kasaragod, Kerala - 671123, India

^a e-mail: ssantra@barc.gov.in

Published online: 19 December 2013

Abstract

Fission fragment (FF) angular distributions for ^6,7Li+^235,238U reactions and mass distributions for ^6,7Li+²³⁸U reactions have been measured at energies near and above the Coulomb barrier. The angle integrated fission cross sections for ⁶Li induced reactions at sub-barrier energies are found to be higher than ⁷Li induced reactions possibly due to larger contribution of breakup induced fission in case of the former compared to the latter. The FF anisotropy for ^6,7Li+²³⁵U was found to be smaller than ^6,7Li+²³⁸U, manifesting the effect of target ground state spin. The statistical saddle point (SSP) model predictions were found to be consistent with the measured FF anisotropy for ^6,7Li+²³⁵U, however they were under-estimated for ^6,7Li+²³⁸U particularly at lower energies. Observation of larger FWHM of FF folding angle distribution and sharp increase in peak to valley ratio for FF mass distribution with the decrease in bombarding energy in ^6,7Li+²³⁸U reactions confirms the presence of breakup induced fission.