Study of the Np-237(n, f)-reaction at MeV neutron energies

The fission fragment properties of the reaction Np-237(n, f) have been inve stigated at IRMM in the neutron energy range E-n = 0.3 to 5.5 MeV, Above E- n = 0.5 MeV, the (TKE) over bar averaged over all fission fragment masses s hows a continuously decreasing trend. The observed variations in the (TKE) over bar as a function of the compound nuclear excitation energy have been attributed to a combination of the changes in the mass yield and (TKE) over bar (A) distributions. A description of the two-dimensional mass-TKE distr ibutions has been obtained in terms of fission modes in the frame of the mu ltimodal random neck-rupture model. The inclusion of the superlong symmetri c mode is necessary to explain the observed dip in the experimental (TKE) o ver bar close to symmetry. (C) 2000 Elsevier Science B.V. All rights reserv ed.