Effect of continuum couplings in fusion of halo11Beon208Pbaround the Coulomb barr

Abstract

The effect of continuum couplings in the fusion of the halo nucleus 11 Be on 208 Pb around the Coulomb barrier is studied using a three-body model within a coupled discretised continuum channels (CDCC) formalism. We investigate in particular the role of continuum-continuum couplings. These are found to hinder total, complete and incomplete fusion processes. Couplings to the projectile 1p 1/2 bound excited state redistribute the complete and incomplete fusion cross sections, but the total fusion cross section remains nearly constant. Results show that continuum-continuum couplings enhance the irreversibility of breakup and reduce the flux that penetrates the Coulomb barrier. Converged total fusion cross sections agree with the experimental ones for energies around the Coulomb barrier, but underestimate those for energies well above the Coulomb barrier.Introduction: The existence and the role of the breakup process of weakly bound projectiles in complete fusion and scattering mechanisms have been extensively investigated in recent years both theoretically [1-6] and experimentally [7][8][9][10][11][12][13][14][15][16], but there is not yet any definitive conclusion. There are contradictory theoretical works which predict either the suppression [1][2][3][4] or the enhancement [5] of the complete fusion cross section due to the coupling of the relative motion of the nuclei to the breakup channel.Recent coupled channels calculations for 11 Be+ 208 Pb [6] have shown that the coupling of the relative motion to the breakup channel has two effects, depending on the value of the bombarding energy, namely (i) a reduction of the complete fusion cross sections at energies above the Coulomb barrier due to the loss of incident flux, and (ii) an enhancement of the complete fusion cross sections at energies below the Coulomb barrier due to the dynamical renormalisation of the nucleus-nucleus potential. Using the isocentrifugal approximation and an incoming boundary condition inside the barrier, this calculation did not include the effect of the projectile's halo structure on the monopole projectile-target potential. Nor did it include the excitation to partial waves other than p 3/2 in the continuum, or the continuumcontinuum and bound excited states couplings in either reaction partner. Moreover, only a small interval of energy for continuum states (up to 2 MeV) was considered.The couplings between continuum states have been shown to be crucial to understand the breakup of 8 B on a 58 Ni target at low energy E lab = 25.8 MeV [19,20]. Therefore, it could be expected that continuum-continuum couplings significantly affect the role of breakup process in fusion of halo nuclei around the Coulomb barrier. We believe that

Low-energy fusion dynamics of weakly bound nuclei: A time dependent perspective

“…A few wave-packet propagations allows one to calculate the converged ICF excitation function in a broad range of incident energies. In contrast to the usual CDCC fusion calculations [17][18][19], this ICF excitation function includes ICF from the projectile bound state(s) [20].…”

Fusion and breakup in the reactions of 6,7Li and 9Be

“…For relatively small values of the impact parameter ( Fig. 1(a)), the projectile nucleus 6 Li is captured by the target before breaking up into α and d, leading to complete fusion. For b=5.5 fm (Fig.…”

“…An important question here is: does the breakup process influence fusion reactions in a similar way as the inelastic process, which leads to subbarrier enhancement [ 1] of fusion cross sections over predictions for a single barrier? In addressing this question, measurements with weakly bound stable nuclei, such as 9 Be, 6 Li, and 7 Li, have been proved to be useful [ 2,3,4]. These beams are currently much more intense than radioactive beams, allowing more precise and extensive experimental studies.…”

“…Process (ii) is referred to as an incomplete fusion reaction, while both of processes (i) and (iii) lead to complete fusion. Calculations based on the continuum-discretized coupled-channels method may account for the total fusion cross section (the sum of all the processes) and/or the separate contribution of process (i) [ 5,6], but it is not easy to compute cross sections for process (iii), that is, the breakup followed by complete fusion. In order to model this process, we need to follow the trajectories of the breakup fragments to determine whether one or both fragments are captured by the target nucleus.…”

Investigation of the influence of incomplete fusion on complete fusion of16O induced reactions at moderate excitation energies

“…It has been a topic of extensive discussion among experimental as well as theoretical nuclear physicists in the past several years [1][2][3][4][5][6]. This discussion has been continuously innovated with the onset of competition between ICF and complete fusion (CF) reactions just above the CB [2,4].…”