Mass asymmetry dependence of angular distribution in237Np(?29 and 44 MeV,f): single particle effect

Abstract

Abstract. Angular distributions of fission products havebeen measured as a function of mass asymmetry in the odd-Z 237Np(c~29~nd44M~v, f) system using a recoilcatcher technique and off-line gamma spectrometry. Higher angular anisotropies were observed for the asymmetric mode products compared to the symmetric mode products at both energies. Average anisotropies for individual modes are lower than those for neighbouring even-even fissioning nucleus 242pu due to odd-nucleon spin effect. Present data have been analysed according to the transition state model assuming two modes of fission with characteristic saddle-shapes, barriers and multichance fission probabilities. It is seen that angular distributions for the symmetric and asymmetric modes are decided at and well past the corresponding saddle points respectively. Oddmucleon spin contribution ((kS)) to the tilting mode variance have been deduced. For 241Am fission, (k 2) values for the asymmetric and symmetric modes are _< 14 and > 14 h 2 respectively. The @2) value averaged over several nuclei from preactinide (2~ to actinide (248Cf) is 11.5 ___ 4.2h 2. Average (k 2) value is in close agreement with the theoretical estimate.