Physics Letters B 634 (2006) 356–361 www.elsevier.com/locate/physletb Disentangling the reaction mechanisms of weakly bound nuclei P.R.S. Gomes a,∗ , I. Padron a,b , E. Crema c , O.A. Capurro d , J.O. Fernández Niello d , G.V. Marti d , A. Arazi d , M. Trotta e , J. Lubian a , M.E. Ortega d , A.J. Pacheco d , M.D. Rodríguez d , J.E. Testoni d , R.M. Anjos a , L.C. Chamon c , M. Dasgupta f , D.J. Hinde f , K. Hagino g a Instituto de Física, Universidade Federal Fluminense, Av. Litoranea s/n, Gragoatá, Niterói, R.J., 24210-340, Brazil b CEADEN, Havana, Cuba c Departamento de Física Nuclear, Universidade de São Paulo, Caixa Postal 66318, 05315-970, São Paulo, S.P., Brazil d Laboratorio Tandar, Departamento de Física, Comisión Nacional de Energía Atómica, Av. del Libertador 8250, (1429) Buenos Aires, Argentina e INFN, Sezione di Napoli, I-80126 Napoli, Italy f Department of Nuclear Physics, Research School of Physical Sciences and Engineering, Australian National University, Canberra ACT 0200, Australia g Department of Physics, Tohoku University, Sendai 980-8578, Japan Received 22 August 2005; received in revised form 26 January 2006; accepted 1 February 2006 Available online 10 February 2006 Editor: V. Metag Abstract Complete and incomplete fusion cross sections for the 9 Be + 144 Sm reaction have been measured at near-barrier energies, using the de- layed X-ray detection technique. At above-barrier energies these show a suppression of complete fusion for this weakly bound projectile on an intermediate mass target. The suppression factor, attributed to 9 Be break-up, was deduced from a comparison of complete fusion yields with coupled-channels calculations, and appears consistent with measured incomplete fusion product yields. At ∼ 10%, it is considerably smaller than the value of ∼ 30% previously found for a 208 Pb target. Simultaneous measurements of elastic and inelastic scattering permit a clearer picture of the reaction mechanisms.  2006 Elsevier B.V. All rights reserved. 1. Introduction The fusion process between heavy ions has been extensively studied during the last four decades. More recently, due to the availability of beams of very weakly bound radioactive nuclei, widespread theoretical and experimental efforts have been de- voted to understanding the influence of break-up of weakly bound nuclei on fusion cross sections [1]. This can lead to dif- ferent behavior in fusion of weakly bound nuclei, compared to the fusion of tightly bound nuclei. There is special interest in this subject, since fusion of very weakly bound and exotic ra- dioactive nuclei are reactions of great astrophysical interest, and may also play a role in the formation of new very heavy iso- topes in future. Conflicting predictions have been made about whether the fusion of such nuclei is enhanced or hindered at * Corresponding author. E-mail address: paulogom@if.uff.br (P.R.S. Gomes). above- and below-barrier energies owing to the strong coupling to the break-up channel [2–7]. Whilst qualitatively a consensus now exist on the existence of some complete fusion suppres- sion at energies above the barrier, for heavy systems, realistic quantitative predictions are still not available. Experimentally, the relatively low intensities of radioac- tive beams presently available make extensive studies difficult. However, it is also valuable to study fusion reactions with weakly bound stable nuclei which have a high break-up prob- ability [8–12]. Here most of the essential features of break-up are found, although radioactive halo nuclei exhibit some prop- erties that are not present in the stable nuclei, such as the very long range of nuclear interaction, with the possible lowering of the fusion barrier, and couplings to the soft dipole resonance (if present). Measurements with stable weakly bound nuclei allow good statistics and precision, and the development of much- needed systematics. The most suitable stable nuclei for such studies are 9 Be, 6 Li and 7 Li, which have break-up threshold en- ergies between 1.48 and 2.45 MeV. 0370-2693/$ – see front matter  2006 Elsevier B.V. All rights reserved. doi:10.1016/j.physletb.2006.02.005