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

The subbarrier fusion cross sections with radioactive ion beams in the systems (10,11) Be + Bi-209 have been measured and compared also with the stable system Be-9 + Bi-209. All three cross sections are similar within experimental accuracy; this is somehow unexpected since, in particular, the fusion process with Be-11 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 Be-10, 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 Be-11,Be-10 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 C code, could be relevant. (C) 2004 Elsevier B.V. All rights reserved.