MASS ASYMMETRY DEPENDENCE OF ANGULAR-DISTRIBUTION IN NP-237(ALPHA(29 AND 44MEV,) F) - SINGLE-PARTICLE EFFECT

Angular distributions of fission products have been measured as a func tion of mass asymmetry in the odd-Z Np-237(alpha(29 and 44 MeV,) f) sy stem using a recoil-catcher technique and off-line gamma spectrometry. Higher angular anisotropies were observed for the asymmetric mode pro ducts compared to the symmetric mode products at both energies. Averag e anisotropies for individual modes are lower than those for neighbour ing even-even fissioning nucleus Pu-242 due to odd-nucleon spin effect . Present data have been analysed according to the transition state mo del assuming two modes of fission with characteristic saddle-shapes, b arriers and multi-chance fission probabilities. It is seen that angula r distributions for the symmetric and asymmetric modes are decided at and well past the corresponding saddle points respectively. Odd-nucleo n spin contribution ([k(2)]) to the tilting mode variance have been de duced. For Am-241 fission, [k(2)] values for the asymmetric and symmet ric modes are less than or equal to 14 and > 14 h(2) respectively. The [k(2)] value averaged over several nuclei from preactinide (Ti-201) t o actinide (Cf-248) is 11.5 +/- 4.2 h(2). Average [k(2)] value is in c lose agreement with the theoretical estimate.