O16-18+O-16 and O-16,O-18 +C-12,C-13 fusion-evaporation reactions at near-Coulomb-barrier energies from statistical model calculations

摘要

Fusion-evaporation reactions of carbon and oxygen isotopes at near-Coulomb-barrier energies are important subjects in nuclear-reaction studies. They are closely related to nucleosynthesis in astrophysics and may provide novel opportunities to study the alpha-clustering effect in light nuclei. In this work, the O16-18+O-16 and O-16,O-18+C-12,C-13 fusion-evaporation reactions are studied by using the statistical model based on the Hauser-Feshbach formalism. It is found that the statistical model with the original Gilbert-Cameron level-density formula typically underestimates the alpha-emission cross sections. To overcome this problem, we introduce for the residual nuclei a new level-density formula with the correction term inspired by theoretical considerations on the alpha-clustering effect. Compared with the original Gilbert-Cameron level-density formula, our statistical-model calculations with the new level-density formula show significant improvements.