H-1, H-2, H-3, He-4 Emission From Ru-96 Nuclei (e-asterisk-similar-to-113 Mev) - Test For Transmission Coefficients In the Evaporation Model

A detailed comparison between measured energy spectra and cross sections of H-1, H-2, H-3, and He-4, evaporated from the composite system 96Ru (E* congruent-to 113 MeV), and the predictions of the statistical model, has been carried out. Results obtained with transmission coefficients derived from optical model (OM), ingoing-wave boundary-condition model (IWBCM) and fusion systematics (FS) are presented. The best overall description of the data is obtained using IWBCM transmission coefficients, with reduced s-wave barriers, including, in the level density, deformations slightly larger than those predicted by the rotating liquid drop model (RLDM). H-2, H-3 yields are well reproduced by IWBCM transmission coefficients, while they are largely overestimated by the OM ones; the failure is found to be related to the imaginary part of the optical potential which accounts for the absorption of nonfusion reactions, in peripheral collisions. No combination of phase space and transmission coefficients is able to reproduce, simultaneously, the low emission barrier and the cross section observed for protons.