Long range effects on the optical model of 6He around the Coulomb barrier

Abstract

We present an optical model (OM) analysis of the elastic scattering data of the reactions 6 He+ 27 Al and 6 He+ 208 Pb at incident energies around the Coulomb barrier. The bare part of the optical potential is constructed microscopically by means of a double folding procedure, using the São Paulo prescription without any renormalization. This bare interaction is supplemented with a Coulomb dipole polarization (CDP) potential, which takes into account the effect of the dipole Coulomb interaction. For this CDP potential, we use an analytical formula derived from the semiclassical theory of Coulomb excitation. The rest of the optical potential is parametrized in terms of Woods-Saxon shapes. In the 6 He+ 208 Pb case, the analysis confirms the presence of long range components, in agreement with previous works. Four-body Continuum-Discretized Coupled-Channels calculations have been performed in order to better understand the features of the optical potentials found in the OM analysis. This study searches to elucidate some aspects of the optical potential of weakly bound systems, such as the dispersion relation and the long range (attractive and absorptive) mechanisms.

Influence of single-neutron stripping on near-barrier He6+Pb208 and HeMarquínez-Durán1, Keeley2, Kemper3 et al. 2017Phys. Rev. C77390View full textAdd to dashboardCite

“…A particular example is projectile breakup which is known to generate a very long absorptive tail in the case of 6 He (see, e.g., Refs. [12,17]). However, because there is no simple model for the breakup of 8 He, we have here limited our study to a comparison of the single-neutron-stripping coupling.…”

“…Coupling to breakup is known to induce long-range absorption for 6 He (see, e.g., Refs. [12,17]) and may be assumed to have a similar, though weaker, effect for 8 He. It follows that the empirical optical model potential is dominated by the long-range breakup coupling effects in the region where it is well determined by the data, despite the influence demonstrated here of the single-neutron-stripping coupling on the elastic scattering angular distributions.…”

“…In specific cases the TELP and exact S-matrix inverted DPPs give similar results, leading to the same physical conclusions (see, e.g., Refs. [12,17] for the case of 6 He breakup), although Refs. [25,26] show that one should be cautious about drawing conclusions from the details of TELP DPPs.…”

Cd110,116(α,α)Kiss1, Mohr2, Fülöp3 et al. 2011Phys. Rev. C

“…So it must be noted that the angular distributions at 16 MeV are not sufficiently sensitive to the width parameter w of the potential. Instead, the fits provide a so-called one-point potential [18,26,41,42]. The smaller (larger) width parameter w is compensated by a larger (smaller) strength parameter λ leading to a fixed potential depth at a large radius (e.g., a value R 0.2 where the real potential depth is 0.2 MeV is derived in [26] from the analysis of elastic scattering excitation functions).…”

Measurements of angular distributions for7Li elastically scattered from58Ni at energies around the Coulomb barrier

“…A clear and specific example of the relevance of elastic scattering experiments is the discovery of the atomic nucleus in 1911, made by Ernest Rutherford. Lately, many experiments and theoretical analyse have been performed using radioactive beams as projectiles to produce a nuclear reaction [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16]. It is well known that in general experiments with halo nuclei are difficult to carry out, mainly because of the low intensities of the respective beams.…”