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We investigate the 9Be+208Pb elastic scattering, breakup and fusion at energies around the Coulomb barrier. The three processes are described simultaneously, with identical conditions of calculations. The 9Be nucleus is defined in an α + α + n three-body model, using the hyperspherical coordinate method. We first analyze spectroscopic properties of 9Be, and show that the model provides a fairly good description of the low-lying states. The scattering with 208Pb is then studied with the Continuum Discretized Coupled Channel (CDCC) method, where the α + α + n continuum is approximated by a discrete number of pseudostates. Optical potentials for the α+208Pb and n+208Pb systems are taken from the literature. We present elasticscattering and fusion cross sections at different energies.

We report on a recent work on the low-energy behavior of the breakup cross section in so far as it has important role in the fusion of weakly bound and halo nuclei at near-barrier energies. We assess the way the nuclear component of this cross section scales with the target mass. In complete accord with previous finding at higher energies we verify that the low energy behavior of the breakup cross section for a given projectile and relative center of mass energy with respect to the Coulomb barrier height scales as the cubic root of the mass number of the target. Surprisingly we find that the Coulomb component of the breakup cross section at these low energies also obeys scaling, but with a linear dependence on the target charge. Our findings are important when planning for experiments involving these exotic nuclei.

Motivated by the strong synergy between structure and nuclear reactions we have performed a phenomenological analysis using available elastic scattering data for collisions of tightly-bound ( 10 Be , 10 B , 10 C , 11 B , 12 C , 16 O ), weakly-bound ( 6 Li , 7 Li , 8 Li , 9 Be ), and exotic ( 6 He , 8 B and 11 Be ) nuclei on 58 Ni and 64 Zn targets at energies close to the Coulomb barrier. After a proper reduction, the cluster configuration and dynamics effects in the total reaction cross section are discussed. Also, an approach based on the interaction distances is used to investigate static and dynamic effects in the elastic scattering of light nuclei. A correlation between the critical interaction distance and binding energy for a given configuration is observed. [ABSTRACT FROM AUTHOR]

We propose the use of neutron poisons in reactions induced by radioactive beams as a test of theoretical models aiming to relate neutron capture in nuclei with neutron surrogate reactions such as (d , p) reactions. We exploit the approximations necessary to obtain a direct relation between the two reactions: surrogate versus neutron capture. We also show how this is intimately related to the momentum distribution of the neutron within the deuteron. The models we use are based on the theory of inclusive breakup reactions commonly employed in the treatment of incomplete fusion and surrogate method. Such theories were developed in the 1980s by Ichimura, Austern and Vincent [Phys. Rev. C32 (1985) 431], Udagawa and Tamura [Phys. Rev. C24 (1981) 1348] and Hussein and McVoy [Nucl. Phys. A445 (1985) 124]. We use these theories to derive an expression for the proton yield in the reaction A (d , p) X. The capture reaction n + A → X is then extracted using reasonable approximations. By recalling an old method proposed by Serber [Phys. Rev.80 (1950) 1098; Proc. Roy. Soc. A208 (1951) 559] we explain how the momentum distribution of neutrons within the deuteron will depend on the short-range dependence of the nucleon–nucleon force. The relevance of our work to nucleosynthesis in the rapid neutron capture process is emphasized. [ABSTRACT FROM AUTHOR]

We investigate three of the most frequently used methods to reduce fusion and total reaction excitation functions. For this purpose, we apply them in two situations. First, we consider theoretical cross sections obtained by single-channel calculations based on standard optical potentials. In this case, the cross sections are not influenced by any particular nuclear property. Thus, the method is successful if the cross sections for different systems are about the same. In the case of fusion excitation functions, we found that the fusion function method works very well, being much better than the other two methods. Regarding total reaction excitation functions, none of the methods is satisfactory. Their reduced reaction cross sections maintain a strong dependence on the atomic and mass numbers of the collision partners. However, they perform reasonably well when compared to similar systems. Next, we use the three methods to reduce experimental fusion and reaction cross sections for many systems, over a broad mass range. Our conclusions are consistent with the ones reached for our theoretical cross sections, resulting from single-channel calculations. That is, the fusion function method is the best for fusion data, whereas none of the three methods works for total reaction. [ABSTRACT FROM AUTHOR]

Existing quantum mechanics methods to study fusion reactions with weakly bound nuclei cannot evaluate separately the complete fusion and the incomplete fusion cross sections. We develop a semiclassical procedure that can calculate these cross sections, apply it to 6,7Li + 209Bi collisions at energies just above the barrier, and show that its predictions for the different fusion cross sections are in good agreement with the data. We find that the contribution from the sequential fusion of the Li fragments to the complete fusion cross section is substantial in the case of 6Li, reaching almost 40% of that from the direct process, which illustrates the importance of calculating correctly the different components of the fusion cross section. [ABSTRACT FROM AUTHOR]

Background: The sub-barrier elastic scattering of heavy ions is discussed. Purpose: We investigate the sensitivity of the Mott cross section to the short-range nuclear interaction. Method: The conventional scattering theory of identical particles is used to discuss the disappearance of Mott oscillations at a certain critical value of the Sommerfeld parameter. This, universal, phenomenon is called "transverse isotropy". Results: It is found that a significant modification of the transverse isotropy arises from the inclusion of the short-range nuclear interaction even at the sub-barrier energies considered. Comparison with existing data on the α + α system is made. Conclusions: We suggest that the study of this lack of Mott oscillation, namely the "transverse isotropy" is a potentially useful mean to study the nuclear interaction. [ABSTRACT FROM AUTHOR]

We show that halo effects enhance fusion cross sections of weakly bound systems, comparing with the situation when there is no-halo. We introduce dimensionless fusion functions and energy variable quantity to investigate systematical trends in the fusion cross sections of weakly bound nuclei at near-barrier energies. We observe very clearly complete fusion suppression at energies above the barrier due to dynamic effects of the breakup on fusion. We explain this suppression in terms of the repulsive polarization potential produced by the breakup. [ABSTRACT FROM AUTHOR]

It is pointed out that the cross-section for the scattering of identical charged bosons is isotropic over a broad angular range around 90° when the Sommerfeld parameter has a critical value, which depends exclusively on the spin of the particle. This effect is not limited to either Coulomb scattering or bosons, and, as illustrated in the shadow scattering of identical hadrons, may lead to interesting physical effects. [ABSTRACT FROM AUTHOR]