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

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.