J.L. Ferrero

Energy-dependent renormalization coefficients of folding-model description of 32S+40Ca elastic scattering

Abstract Angular distributions for the elastic scattering of 32 S on 40 Ca have been measured at 32 S bombarding energies of 100, 120 and 151.5 MeV. Optical model analyses were performed using Woods-Saxon and double-folding potentials which yield a good description of the angular distributions. The energy dependence of the phenomenological optical potentials and renormal- ization coefficients of the double-folded potential were found. These results are anomalous in comparison with the elastic scattering of heavy projectiles (with A > 12) on the same target nucleus.

A Monte Carlo based method of including gamma self-absorption for the analysis of environmental samples

We propose a new method to calculate the full-energy-peak efficiency of Ge(Hp) detectors, including gamma self-absorption, using a Monte Carlo technique. We have studied several samples geometries, which are the most commonly used in environmental radioactivity, Petri vial and Marinelli beakers, supposing different densities for the material in the sample, between 0.4 and 1.6 g/cm3. For each geometry we have found an important change of self-absorption on density and we have calculated the dependence of full-energy-peak efficiency on sample density for a set of energies between 100 and 2000 keV.

Backscattering and self-absorption corrections in the measurement of alpha-emitters in 2π geometry

Abstract Monte Carlo simulation has been developed to model the slowing down and scattering of alpha particles in amorphous media so that corrections for backscattered and absorbed particles can be determined for 2π geometry measurements. These calculations are based on the total stopping powers and the Rutherford scattering law, and the resulting energy spectra are in good agreement with experimental measurements.

The threshold anomaly in the 32S + 40Ca interaction☆

Abstract Angular distributions for elastic scattering of 32 S by 40 Ca, inelastic scattering leading to the first 2 + state in 32 S and the first 3 − state in 40 Ca and one-neutron stripping reactions have been measured at E lab =90 and 110 MeV. Angular distributions for alpha stripping reactions have been measured at E lab =90, 100 and 110 MeV. The data have been analyzed in terms of the double-folding model using the coupled-channel approximation for inelastic scattering. The energy dependence of the renormalization coefficient of the folding potential founded in a previous paper has been confirmed at these new energies and is consistent with the dispersion relation of Mahaux et al . The influence of the coupling of inelastic and transfer channels on the renormalization coefficient has been found to be important. The energy dependence of the potential diminishes with increasing coupling strength.

Monte Carlo simulation of alpha spectra in low-geometry measurements

Abstract Monte Carlo simulation of alpha spectra obtained with semiconductor detectors in low-geometry has been developed. The proposed method reproduces adequately experimental spectra of alpha emitters by taking into account the energy losses and trajectory changes of alpha particles as consequences of their interactions in the source, backing and detector.

One-neutron transfer contribution to the elastic 32 S+ 32S scattering at Einc = 91.3 MeV☆

Abstract The elastic scattering differential cross section for 32 S incident on 33 S at E inc = 91.3 MeV has been measured. The observed backward oscillations are successfully described by explicit inclusion of a parity-dependent term in the real potential for the optical-model calculations of the elastic scattering. To investigate possible sources of the parity-dependent term, the backward oscillations were also interpreted as being produced by the interference between the elastic amplitude and the one-neutron elastic one-step transfer process.

Dispersion relation for microscopic heavy-ion potentials and description of elastic scattering above the coulomb barrier for 32S on 40Ca

Abstract The closure approximation model is used to study the dispersion relation for local potentials when the Green function is calculated for an hermitian and non-hermitian effective hamiltonian. In the same model the angular distributions for elastic scattering of 32 S on 40 Ca are calculated at 90, 100, 110, 120 and 151.5 MeV. Comparison with data shows the ability of the model to describe the imaginary and polarization potentials.

Inelastic scattering of 32S on 28Si

Abstract The elastic and inelastic cross sections of 32 S on 28 Si at 77, 90 and 97.09 MeV incident energies have been measured. The excitation of the first 2 + and 3 − levels in both nuclei as well as the [2 1 + , 2 1 + ] mutual excitation were studied. The angular distributions are reproduced by coupled-channel calculations. The influence of various reaction mechanisms have been studied. Strong high-order effects are predicted. Total reaction and inelastic cross sections for low-lying excited states have been extracted.

Surface absorption in the 32S + 24Mg interactions at energies near the coulomb barrier

Abstract Elastic scattering of 32S on 24Mg has been measured at 65.0, 75.0, 86.3, 95.0 and 110.0 MeV lab energies, and the data were systematically analyzed with semi-phenomenological potentials. Using microscopic potentials we found similar results at the two lowest incident energies, for which we have compared both the microscopic and semi-phenomenological potentials. It appears that the absorption takes place in a narrow range at the nuclear surface and is mainly due to the low-lying collective surface states.

Sub- and near-barrier fusion potentials and cross sections

Abstract In a closure approximation model which has been used to calculate the absorptive potential of elastic-scattering, we are able to extract the contribution due to absorption in direct non-elastic channels. Following the one-channel models of fusion we are therefore able to calculate, by subtraction, the potential WF describing absorption in fusion channels. The model has been applied to the system 16O + 208Pb. Our potential WF has, in sub- and near-barrier domains, a very short range, in agreement with empirical analyses of fusion, but this short range varies with energy. The calculated fusion cross sections reproduce the data quite well, in particular in the far sub-barrier region where the energy dependence of the range is crucial to reproduce the experimental values.