Study on the 143Nd (nα)140Ce reaction, caused by fast neutrons

The 143Nd(nα)140Ce reaction caused by 14-18 MeV neutrons is investigated. The spectrum of alpha-particles at Esub(n) = 18 MeV and the angular distributions of aplha-particles at Esub(n) = 18 MeV 14 Mev are presented. Transitions to the ground and first excited states are observed. The angular distributions of alpha-particles are strongly assymmetrical with overwhelming predominance of forward angles, which is typical of direct processes. The energy spectrum is compared with the calculations according to the statistical and preequilibrium alpha-particle emission models. It is not possible to describe the reaction in question with account for these mechanisms. The alpha-cluster emission mechanism must be considered