[en] In recent papers, we have proposed two different models to calculate fusion cross sections for heavy-ion systems, based on coupled-channels calculations involving harmonic vibrations of the nuclear densities. The parameter-free Sao Paulo potential is assumed as the bare interaction and, therefore, the calculations are performed without any adjustable parameter. In the present work, we compare the results of these models in accounting for fusion data of approximately 60 different systems

[en] A microscopic calculation of the optical potential for nucleon-nucleus scattering has been performed by explicitly coupling the elastic channel to all the particle-hole (p-h) excitation states in the target and to all relevant pickup channels. These p-h states may be regarded as doorway states through which the flux flows to more complicated configurations, and to long-lived compound nucleus resonances. We calculated the reaction cross sections for the nucleon induced reactions on the targets ^40,48Ca, ⁵⁸Ni, ⁹⁰Zr and ¹⁴⁴Sm using the QRPA description of target excitations, coupling to all inelastic open channels, and coupling to all transfer channels corresponding to the formation of a deuteron. The results of such calculations were compared to predictions of a well-established optical potential and with experimental data, reaching very good agreement. The inclusion of couplings to pickup channels was an important contribution to the absorption. For the first time, calculations of excitations account for all of the observed reaction cross-sections, at least for incident energies above 10 MeV.

[en] Here, we investigate different formulations of the transmission coefficient T_c, including the form implied by Moldauer’s “sum rule for resonance reactions” and the Moldauer-Simonius form. Within these different formulations, we compute the neutron transmission coefficients in the resolved and unresolved resonance regions, allowing a direct comparison with the transmission coefficients computed using an optical model potential. For nuclei for which there are no measured resonances, these approaches allow one to predict the average neutron resonance parameters directly from the optical model and level densities. Some of the approaches are valid in both the strong and weak coupling limits (i.e., any value of the average width and mean level spacing). Finally, both the Moldauer-Simonius and Moldauer’s Sum Rule forms approaches suggest that superradiance, that is, the quantum chaotic enhancement of certain channels, may be a common phenomena in nuclear collisions. Our results suggest why superradiance has been previously overlooked. We apply our approach to neutron reactions on the closed shell ⁹⁰Zr nucleus and the mid-shell ¹⁹⁷Au nucleus.

[en] The US Nuclear Data Program is charged with collecting, analyzing and archiving information critical to basic nuclear research and to the development of nuclear technologies. Users of nuclear data require detailed uncertainty information for a variety of reasons. In this paper, we review some of the main aspects of the generation and use of uncertainty information, linking to structure, astrophysics, and reaction data. (paper)

[en] The coupled-channel theory is a natural way of treating nonelastic channels, in particular those arising from collective excitations, defined by nuclear deformations. Proper treatment of such excitations is often essential to the accurate description of reaction experimental data. Previous works have applied different models to specific nuclei with the purpose of determining angular-integrated cross sections. In this work, we present an extensive study of the effects of collective couplings and nuclear deformations on integrated cross sections as well as on angular distributions in a consistent manner for neutron-induced reactions on nuclei in the rare-earth region. This specific subset of the nuclide chart was chosen precisely because of a clear static deformation pattern. We analyze the convergence of the coupled-channel calculations regarding the number of states being explicitly coupled. Inspired by the work done by Dietrich et al., a model for deforming the spherical Koning-Delaroche optical potential as function of quadrupole and hexadecupole deformations is also proposed. We demonstrate that the obtained results of calculations for total, elastic and inelastic cross sections, as well as elastic and inelastic angular distributions correspond to a remarkably good agreement with experimental data for scattering energies above around a few MeV

[en] In a recent article, we calculated fusion cross sections for systems involving even-even nuclei based on a method that takes into account the couplings to a complete set of states for surface vibrations of the nuclear densities. The predictions were obtained without using any adjustable parameter, and are in good agreement with the experimental results for most of the systems, even at sub-barrier energies. In the present work, we extend these calculations to systems involving nuclei with odd number of protons and/or of neutrons

[en] A microscopic calculation of reaction cross sections for nucleon-nucleus scattering was performed by coupling the elastic channel to all particle-hole excitations in the target and one-nucleon pickup channels. The particle-hole states may be regarded as doorway states through which the flux flows to more complicated configurations, and subsequently to long-lived compound nucleus resonances. Target excitations for ^40,48Ca, ⁵⁸Ni, ⁹⁰Zr, and ¹⁴⁴Sm were described in a random-phase framework using a Skyrme functional. Reaction cross sections obtained agreed very well with experimental data and predictions of a fitted optical potential. Couplings between inelastic states were found to be negligible, while the pickup channels contribute significantly. For the first time observed absorptions are completely accounted for by explicit channel coupling, for incident energies between 10 and 40 MeV.

[en] A microscopic calculation of reaction cross sections for nucleon-nucleus scattering has been performed by explicitly coupling the elastic channel to all particle-hole excitations in the target and one-nucleon pickup channels. The particle-hole states may be regarded as doorway states through which the flux flows to more complicated configurations, and subsequently to long-lived compound nucleus resonances. Target excitations for ^40,48Ca, ⁵⁸Ni, ⁹⁰Zr, and ¹⁴⁴Sm were described in a random-phase framework using a Skyrme functional. Reaction cross sections obtained agree very well with experimental data and predictions of a state-of-the-art fitted optical potential. Couplings between inelastic states were found to be negligible, while the pickup channels contribute significantly. The effect of resonances from higher-order channels was assessed. Elastic angular distributions were also calculated within the same method, achieving good agreement with experimental data. Observed absorptions are completely accounted for by explicit channel coupling, for incident energies between 10 and 70 MeV, with consistent angular distribution results.

[en] We have calculated fusion cross sections for 64 heavy-ion systems based on a method that takes into account the couplings to a complete set of states for surface vibrations of the nuclear densities. For the nuclear interaction we have assumed the parameter-free Sao Paulo potential. The predictions have been obtained without using any adjustable parameter, and are in good agreement with the experimental results for most of the systems, even at sub-barrier energies

[en] The inelastic, two-neutron and α transfer and quasielastic cross sections for the ¹⁸O+¹¹⁰Pd system have been measured in the near barrier region (40 MeV ≤E_lab≤58 MeV). The experiments were performed in the Sao Paulo Pelletron laboratory. Coupled-channel analysis of the experimental data was performed using the Sao Paulo potential as a microscopic bare interaction. In the calculations, low-lying inelastic excitations, one- and two-neutron and α transfers to the target were considered as the main couplings, with no extra surface absorption. The agreement between the theoretical results and the experimental data is good. The role played by the coupled channels is very different in comparison with similar data analyses for the closed-shell region around ⁵⁸Ni