Level Excitation Function Data for Fast Neutron Scattering on Actinide Nuclei Calculated with the Unified Statistical S-Matrix Formalism

Abstract

Results from analyses of the most recent 232Th, 238U, 240Pu and 242Pu (n,n′) level cross-section data from threshold to 2.5 MeV for inelastic neutron scattering to collective (rotational and guadrupole or octupole vibrational) levels of these deformed actinide nuclei are presented, as calculated with the unified statistical S-matrix formalism using the Bruyeres optical potential and deformation parameters. The computations with the programme “NANCY” allowed for competition from other neutron exit channels, and have been corrected for fission and radiative-capture competition. The treatment took account of strong coupling (with strongly or weakly absorbing channels) in a comprehensive, consistent, cohesive approach that involved an intimate combination of direct interaction and fluctuation contributions to the cross section. The good fits obtained for (n,n′) level excitation functions to quite high lying levels, especially when (n,n′) measured data were combined with results from (n,n′γ) studies, prompt the application of such calculations to cases in which experimental data are unavailable or unobtainable.