E.S. Rossi

Toward a global description of the nucleus-nucleus interaction

Extensive systematizations of theoretical and experimental nuclear densities and of optical potential strengths extracted from heavy-ion elastic scattering data analyses at low and intermediate energies are presented. The energy dependence of the nuclear potential is accounted for within a model based on the nonlocal nature of the interaction. The systematics indicates that the heavy-ion nuclear potential can be described in a simple global way through a double-folding shape, which basically depends only on the density of nucleons of the partners in the collision. The possibility of extracting information about the nucleon-nucleon interaction from the heavy-ion potential is investigated.

A parameter-free optical potential for the heavy-ion elastic scattering process☆

Abstract Thirty elastic scattering angular distributions for seven heavy-ion systems, in wide energy ranges, have been studied with the aim of systematizing the optical potential, real and imaginary parts, in a global way. The framework is: (i) an extensive systematization of nuclear densities, (ii) the energy dependence of the bare potential accounted by a model based on the nonlocal nature of the interaction, and (iii) the real and imaginary parts of the optical potential assumed to have the same radial shape.

Experimental determination of the ion-ion potential in the N = 50 target region: A tool to probe ground-state nuclear densities

Abstract Precise elastic and inelastic differential cross sections have been measured for the 16 O + 88 Sr , 90,92 Zr, 92 Mo systems at sub-barrier energies. From a coupled channel data analysis, the corresponding “experimental” bare potentials have been determined. The comparison of these potentials with those derived from double-folding theoretical calculations and the high energy (96 Mev/nucleon) elastic scattering data analysis indicate that the method is a very sensitive probe of the ground-state nuclear densities in the surface region.

Effect of the 18O nuclear density on the nuclear potentials of the 18O+58,60Ni systems

Abstract Quasi-elastic, inelastic, one- and two-neutron transfer differential cross sections have been measured for the 18 O+ 58,60 Ni systems at sub-barrier energies. The corresponding bare potentials have been determined at interaction distances larger than the respective barrier radii, and the results have been compared with those previously obtained for systems involving the 16 O as projectile. The detected difference between the 18 O and 16 O nuclear potentials has allowed the determination of the nuclear density that corresponds to the two extra neutrons of the 18 O nucleus.

The heavy-ion nuclear potential: determination of a systematic behavior at the region of surface interaction distances

Abstract Precise elastic scattering differential cross sections have been measured for the 16 O + 120 Sn , 138 Ba , 208 Pb systems at sub-barrier energies. The corresponding “experimental” nuclear potentials have been determined at interaction distances larger than the Coulomb barrier radii. These experimental potentials have been compared with our earlier results for other systems, and with theoretical calculations based on the double-folding and liquid-drop models. We have shown that the nuclear potentials have a systematic behavior at the surface region. The present results for the 16 O + 208 Pb system are used to extend earlier studies of the dispersion relation to sub-barrier energies.

Isotopic dependence of the ion-ion potential in the systems 16O+58,60,62,64Ni☆

Abstract Precise measurements of the elastic and inelastic scattering cross sections for the systems 16 O+ 58,60,62,64 Ni at the sub-barrier energies were made. Coupled-channel analysis were performed. The isotopic dependence of the resulting ion-ion potentials is compared with theoretical calculations using the double-folding method with the M3Y as the nucleon-nucleon interaction and shell-model densities.

Experimental investigation of the ion-ion potential for the 16O + 60 Ni system at large interaction distances

Abstract Precise measurements of the elastic and inelastic scattering cross sections for the 16 O + 60 Ni system at the sub-barrier energies were made. Coupled channel analysis of the only two open channels were performed. The behaviour of the ion-ion potential at large distances is discussed.

Elastic, inelastic scatterings and transfer reactions for 16,18O on 58Ni described by the São Paulo potential

We have used a parameter - free potential, obtained from data analysis at sub-barrier energies, to explain our measurements of elastic and several inelastic scattering cross sections for the 16,18O + 58Ni systems at an energy above the barrier. The data were analyzed through extensive coupled-channel calculations. Transfer cross sections could also be explained by the same interaction, which is consistent with the more fundamental Sao Paulo potential.

Evidence of a slight nuclear transparency in the alpha-nucleus systems

In earlier works, we proposed a model for the nuclear potential of the α + α and α + ¹²C systems. In addition, this theoretical model successfully described data related to the elastic and inelastic scattering processes as well as resonances that correspond to the capture reaction channel. In the present work, we extend the same model to obtain bare nuclear potentials for several α-nucleus systems. We adopt this parameter-free interaction to analyze fusion, elastic, and inelastic scattering data within the context of the coupled-channel formalism. Our results indicate that, for these systems, the absorption of flux of the elastic channel at internal distances of interaction is not complete. In addition, we present new experimental angular distributions for the 2⁺ inelastic target excitation of α on ¹²⁰,¹³⁰Te.

Measurement of fusion cross sections for 16O+16O

In earlier works, the fusion cross section for the 16O+16O reaction has been measured using different techniques. In the present work, we have obtained an experimental excitation function for 16O+16O using γ-ray spectroscopy. The measurements were performed at center-of-mass energies between 8.28 and 12.25 MeV. The theoretical predictions obtained with a coupled-channel model are consistent with the experimental data. From our analyses, the extrapolated S-factor value at 6.6 MeV, corresponding to the Gamow peak energy for core oxygen burning conditions, is about 3.6 × 1025 MeV barn.