Subbarrier fusion in the systems ^11,10Be+²⁰⁹Bi

Abstract

The subbarrier fusion cross sections with radioactive ion beams in the systems ^10,11Be+²⁰⁹Bi have been measured and compared also with the stable system ⁹Be+²⁰⁹Bi. All three cross sections are similar within experimental accuracy; this is somehow unexpected since, in particular, the fusion process with ¹¹Be should be influenced by its halo structure and small binding energy and could behave in a different way from the other two Be isotopes, in particular from ¹⁰Be, well bound. Extensive calculations were undertaken within the formalism of continuum discretized coupled channel (CDCC) that considered only the coupling to two-body breakup, into n+core, of the projectile with excitation to continuum up to 10 MeV. The results are in agreement with the ^11,10Be experimental data except at low energy where the cross sections could be influenced by target/projectile collective excitations. The CCFULL theoretical approach, compared to CDCC, seems to reproduce better the subbarrier region and worse the above barrier one. The ⁹Be cross sections are all underestimated by the CDCC approach while are well reproduced by CCFULL calculations. This suggests that, in this last case, the schematization of the breakup process into 2 only fragments maybe is not adequate and/or other excitations, properly handed by the CCFULL code, could be relevant.