Symmetry Aspects of Fission Fragment Mass Distribution in 238U(18O,F) Reaction

Abstract

Fine structure dips in the fission fragment mass distribution in 238U(18O; f ) reaction arise mainly due to breakdown of the spin-isospin symmetry. The average proton-neutron interaction for each decay mode is calculated by using double differences of binding energies, It is shown that its decreasing trend at N=82 has direct relevance with the breakdown of spin-isospin symmetry. The maxima in the p-n interaction correspond to partial restoration of spin-isospin symmetry and therefore, help in limiting the number of neutrons evaporated in each decay channel. Also, calculations based on the asymmetric two-center shell model explain not only the observed mass distribution nicely but suggests a possible value of extending these experiments beyond their present mass limits.