NEUTRON EMISSION CROSS-SECTIONS AT LOW BOMBARDING ENERGIES AND THE NOVELTY IN MULTISTEP COMPOUND REACTION MODEL

Inelastic neutron emission at 6.7 and 20 MeV incident energies has bee n measured for monoisotopic samples of Ho-165 and Ta-181. Time-of-flig ht spectra were taken at several angles between 15-degrees and 145-deg rees using a beam-swinger spectrometer. The cross sections are average d over 1 MeV energy bins. The 20 MeV data, when compared with the quan tum-mechanical statistical multistep calculations have revealed a magn itude problem in the existing theories. A gradual or ''multistep'' abs orption in the entrance channels is proposed as a way out of the diffi culty. This modification turns out to be sufficient for an adequate de scription of the experimental data.