Abstract
Nuclear model calculations of discrete γ-ray production cross sections produced in () and () reactions were made as a function of incident neutron energy from MeV to 35 MeV and compared with new experimental results using the large-scale Compton-suppressed germanium array for neutron induced excitations (GEANIE) at LANSCE. The Hauser-Feshbach reaction code GNASH, incorporating the spin distribution for the preequilibrium process calculated with the Feshbach-Kerman-Koonin (FKK) quantum-mechanical preequilibrium theory, was used to calculate partial γ-ray transition cross sections. The comparisons of calculated and experimental data demonstrate that, the FKK model for preequilibrium leads a better overall reproduction of the experimental data above MeV, where preequilibrium processes are important. The FKK calculation predicts a strong reduction in the high-spin state population in by inelastic scattering. Population of low-spin states was also affected, however the change in the low-lying 983.5-keV () state production is small because almost all γ-ray decay cascades feed this transition. In addition, the FKK calculation has a significant impact on the partial γ-ray transition cross sections for the () reaction above MeV. The calculated cross sections for high-spin states in are reduced, and those from the low-spin states are enhanced, in agreement with the experimental cross section data.
6 More- Received 1 March 2007
DOI:https://doi.org/10.1103/PhysRevC.75.054612
©2007 American Physical Society