K. M. Abdo

Direct and compound nuclear contributions to the 13C(6Li, t) reaction at Elab = 25 MeV☆

Abstract The reaction 13 C( 6 Li, t) 16 O has been studied in the incident energy range 24–26 MeV. Complete angular distributions have been measured at E 6 Li , = 25 MeV in the angular range θ lab = 8°–172°, with the reaction 6 Li( 13 C, t) 6 O being used for the backward angle measurements. Cross sections for evaporation residues from the fusion of the 6 Li + 13 C system have been measured in the incident 6 Li energy range 9.2–35.1 MeV. Compound nuclear contributions to the transfer cross sections have been calculated using the Hauser-Feshbach statistical theory with the assumption that the compound-nucleus formation cross section is equal to the measured fusion cross section. By comparison of the compound nuclear calculations with backward angle data it is found that the sharp cutoff approximation commonly used to represent the initial angular momentum distribution of the compound nucleus is not adequate for the 13 C( 6 Li, t) 16 O reaction. Good fits to the backward angle data can be obtained by using a smooth cutoff approximation. The forward angle cross sections have been compared with exact finite-range distorted-wave Born approximation calculations to extract transferred angular momenta and spectroscopic strengths. The present results differ from those of an earlier study. These differences are due to the inclusion of forward angle data in the present study.

Resonances in 12C + 13C at Ec.m. = 9.4 and 10.3 MeV observed in the total fusion cross section☆

Abstract The 12 C + 13 C total fusion cross section has been measured from E c.m. = 8.8 to 10.9 MeV to search for evidence of two resonances previously reported at 9.4 and 10.3 MeV on the basis of elastic scattering data. Enhancements of about 6 % are observed in the total fusion cross section at E c.m. = 9.35 + 0.05 and 10.21±0.05 MeV. If the previously assigned resonance parameters are correct, the observed resonant contribution to the fusion cross section at 10.3 MeV is too large to be consistent with the non-resonant absorption of ∼ 80 % predicted from available optical-model parameters. It is concluded that these two resonances in 12 C+ 13 C are comparable to the strongest resonances observed in 12 C + 12 C and 12 C + 16 O. The apparent weakness of 12 C+ 13 C resonances in measured reaction cross sections is expected on the basis of simple angular momentum considerations.