Coupled-channel effects in elastic scattering and near-barrier fusion induced by weakly bound nuclei and exotic halo nuclei

Abstract

The influence on fusion of coupling to the breakup process is investigated for reactions where at least one of the colliding nuclei has a sufficiently low binding energy for breakup to become an important process. Elastic scattering, excitation functions for sub-and near-barrier fusion cross sections, and breakup yields are analyzed for 6,7 Li+ 59 Co. Continuum-Discretized Coupled-Channels (CDCC) calculations describe well the data at and above the barrier. Elastic scattering with 6 Li (as compared to 7 Li) indicates the significant role of breakup for weakly bound projectiles. A study of 4,6 He induced fusion reactions with a three-body CDCC method for the 6 He halo nucleus is presented. The relative importance of breakup and bound-state structure effects on total fusion is discussed.

Coupled-Channel Effects in Collisions Between Heavy Ions Near the Coulomb Barrier

“…Thess results are consistent with rather low breakup cross sections measured for the 6,7 Li+ 59 Co reactions even at incident energies larger than the Coulomb barrier [39,40,41]. But the coupling of the breakup channel is extremely important for the CDCC analysis of the angular distributions of the elastic scattering [47] as shown in Fig. 4 out (dashed lines) 6,7 Li → α + d,t breakup couplings.…”

“…[47,49] indicate only a small enhancement of total fusion for the more weakly bound 6 Li below the Coulomb barrier (see curves of Fig.2), with similar cross sections for both 6,7 Li+ 59 Co reactions at and above the barrier [24]. It is interesting to notice, however, that the same conclusions have been reached for other targets such as 24 Mg [26] and 28 Si [25,27,28] as can be clearly seen in the plot of Fig.…”

“…It is therefore appropriate to use the Continuum-Discretized Coupled-Channel (CDCC) approach [47,48,49,50] to describe the influence of the breakup channel in both the elastic scattering and the fusion process at sub-barrier energies.…”

Analytical transformed harmonic oscillator basis for continuum discretized coupled channels calculations

“…The 6 Li nucleus is assumed here to be composed of two fragments, α + d, as has usually been done in previous studies (see, for example, Refs. [6][7][8][9]). An important difference with respect to the deuteron case is the presence of a d-wave resonance in the 6 Li continuum.…”

“…Although originally designed to account for the effect of the breakup channels in direct nuclear reactions involving deuterons [1][2][3], it soon proved to be a useful tool to describe reactions induced by other weakly bound nuclei that could be to some extent described within a two-cluster model such as 6 Li [4][5][6][7][8][9] or 7 Li [9][10][11][12][13] and, more recently, the scattering of exotic nuclei such as 8 B [14][15][16][17], 7 Be [13], or 11 Be [18,19]. The CDCC method has been extended lately to describe the scattering of three-body projectiles and has successfully described the elastic scattering of 6 He [20][21][22][23].…”