Optical potentials of halo and weakly bound nuclei

The optical potential of halo and weakly bound nuclei has a long range part due to the coupling to breakup that damps the elastic scattering angular distributions at all angles for which the effect of the nuclear interaction is felt. In charge exchange reactions leading to a final state with a halo nucleus, the surface potential is responsible for a strong reduction in the absolute cross section. We show how the halo effect can be simply estimated semiclassically and related to the properties of the halo wave function. Assuming an exponential tail for the imaginary surface potential we show that the most important parameter is the diffusness $\alpha$ of the potential which is directly related to the decay length $\gamma_i$ of the initial wave function by $\alpha\approx(2\gamma_i)^{-1}$Comment: 18 Latex pages, 1 table, 1 eps figures, 3 ps figures. accepted to Nucl. Phys.

The Quantum Liquid of Alpha Clusters

Within the variational approach of Bose liquids we analyze the g.s. energy of charge neutral alpha matter at $T$=0. As a prerequisite for such calculation we take from the literature or propose new \alp-\alp potentials that are particularly suitable for this task, i.e. posses a repulsive core and/or reproduce the low energy scattering data and the resonance properties of the \alp-\alp system. The alpha matter EOS is then obtained with the HNC method using Pandharipande-Bethe correlation derived variationally in the lowest order expansion of the energy functional or a simple gaussian function with a healing range determined by the normalization of the radial distribution function in the lowest order. We show that saturation is achieved only via repulsive and shallow potentials that are not consistent with the scattering and resonance constraints.Comment: 8 pages, 4 figure

Cluster Expansion of Cold Alpha Matter Energy

In the cluster expansion framework of Bose liquids we calculate analytical expressions of the two-body, three-body and four-body diagrams contributing to the g.s. energy of an infinite system of neutral alpha-particles at zero-temperature, interacting via the strong nuclear forces exclusively. This is analytically tractable by assuming a density dependent two-body correlation function of Gaussian type. For the alpha-alpha potential we adopt the phenomenological Ali-Bodmer interaction and semi-microscopic potentials obtained from the Gogny force parametrizations. We show that under such assumptions we achieve a rapid convergence in the cluster expansion, the four-body contributions to the energy being smaller than the two-body and three-body contributions by at least an order of magnitude.Comment: 22 pages, 13 figure

Refractive effects in the scattering of loosely bound nuclei

A study of the interaction of loosely bound nuclei 6,7Li at 9 and 19 AMeV with light targets has been undertaken. With the determination of unambiguous optical potentials in mind, elastic data for four projectile-target combinations and one neutron transfer reaction 13C(7Li,8Li)12C have been measured on a large angular range. The kinematical regime encompasses a region where the mean field (optical potential) has a marked variation with mass and energy, but turns out to be sufficiently surface transparent to allow strong refractive effects to be manifested in elastic scattering data at intermediate angles. The identified exotic feature, a "plateau" in the angular distributions at intermediate angles, is fully confirmed in four reaction channels and interpreted as a pre-rainbow oscillation resulting from the interference of the barrier and internal barrier farside scattering subamplitudes.Comment: 19 pages, 14 figures, 3 tables to submit to Phys. Rev.

Imaginary part of the C 9 − Be 9 single-folded optical potential

In a recent publication we have argued that using two very successful n\text{\ensuremath{-}}^{9}\mathrm{Be} optical potentials [A. Bonaccorso and R. J. Charity, Phys. Rev. C 89, 024619 (2014)] and microscopic projectile densities, it is possible to build a single-folded (light-) nucleus-$^{9}\mathrm{Be}$ imaginary optical potential which is more accurate than a double-folded optical potential. By comparing to experimental reaction cross sections, we showed for $^{8}\mathrm{B},\phantom{\rule{0.16em}{0ex}}^{8}\mathrm{Li}$, and $^{8}\mathrm{C}$ projectiles, that a very good agreement between theory and data could be obtained with such a ``bare'' potential, at all but the lowest energies where a small semimicroscopic surface term was added to the single-folded potential to take into account projectile breakup. In this paper we extend this study to the case of $^{9}\mathrm{C}$ projectiles and assess the sensitivity to the projectile density used. We then obtained the modulus of the nucleus-nucleus $S$ matrix and parametrize it in terms of a strong-absorption radius ${R}_{s}$ and finally extracted the phenomenological energy dependence of this radius. This approach could be the basis for a systematic study of optical potentials for light exotic nuclei scattering on light targets and/or parametrizations of the $S$ matrix. Furthermore our study will serve to make a quantitative assessment of the description of the core-target part of knockout reactions, in particular their localization in terms of impact parameters