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We develop a semi-microscopic model to describe transfer reactions. For the sake of simplicity, we focus on nucleon-transfer reactions, but the theory can be generalized to other transfer processes. The model makes use of overlap integrals computed in the microscopic Resonating Group Method (RGM). This technique is based on an effective nucleon-nucleon interaction and on the cluster approximation. It avoids the choice of a nucleon-core potential for the residual nucleus, and does not require any fit of spectroscopic factors. The model is therefore free of parameter. For the entrance channel, we use the Continuum Discretized Coupled Channel (CDCC) method where the breakup of the projectile is simulated by approximations of the continuum. This technique is well known for elastic scattering and for breakup reactions. It is well adapted to weakly bound nuclei such as the deuteron. The model is applied to the 14 C (d , p) 15 C and 6 He (d , n) 7 L i reactions with RGM wave functions of 15 C and of 7 Li. The 15 C nucleus is described by 14 C (0 + , 2 +) + n configurations whereas 7 Li contains the α + t , 6 He (0 +) + p and 6 Li (1 + , 0 +) + n configurations. The spectroscopic factors are in fair agreement with the literature. We show that the model provides an excellent description of the transfer cross sections considering that no parameter is adjusted. [ABSTRACT FROM AUTHOR]

We investigate 9Be + 208Pb elastic scattering, breakup, and fusion at energies around the Coulomb barrier. The three processes are described simultaneously, with identical conditions of calculations. The 9Be nucleus is defined in an α + α + n three-body model, using the hyperspherical coordinate method. We first analyze spectroscopic properties of 9Be and show that the model provides a fairly good description of the low-lying states. The scattering with 208Pb is then studied with the continuum discretized coupled channel method, where the α + α + n continuum is approximated by a discrete number of pseudostates. The use of a three-body model for 9Be improves previous theoretical works, where 9Be is assumed to have a two-body structure (8Be + n or He5+α), although neither 8Be nor He5 are bound. Optical potentials for the α+208Pb and n+208Pb systems are taken from the literature. We present cross sections at different energies, and we investigate the convergence with respect to the truncation of the α + α + n continuum. In general, good agreement with experiment is obtained, despite no parameter fitting being made. We show that continuum effects increase at low energies, and we confirm that breakup channels enhance the fusion cross sections below the Coulomb barrier. [ABSTRACT FROM AUTHOR]

Background: In the traditional continuum discretized coupled-channels (CDCC) method, the clusters of the projectile are structureless. Exotic nuclei exhibit unusual properties and often show significant couplings to the continuum. Therefore, reaction models that consider a more accurate structure of the projectile are often preferable. A microscopic description of the projectile, based on an effective nucleon-nucleon (NN) interaction, in a microscopic CDCC (MCDCC) model [Descouvemont and Hussein, Phys. Rev. Lett. 111, 082701 (2013)] has been successfully applied to 7Li+208Pbscattering. Purpose: The MCDCC method is applied to low-energy elastic scattering of 17F, 17O, and 19F on 58Ni and 208Pb targets. The goal of the calculations is twofold: to test the adequacy and the accuracy of the MCDCC model for heavier projectiles and to study the contribution of various channels to the elastic scattering cross sections. Methods: The elastic scattering cross sections are calculated by using the MCDCC method. The nucleon-target optical potential is folded with the projectile densities resulting from an effective NN interaction, which includes central nuclear, spin-orbit, and Coulomb terms. Discretization of the continuum is achieved via the pseudostate method. Coupled equations are solved by using the R-matrix method on a Lagrange mesh. Results: For the test case of 17F at 10 MeV/nucleon, the cross sections are weakly sensitive to the choice of the effective NN interaction. Three different energy-dependent optical nucleon-target potentials provide a similar reasonable agreement with data. Just below the Coulomb barrier, the MCDCC significantly underestimates the cross sections at larger angles. The coupling to the continuum is not significant in most of the assessed cases. Conclusions: The MCDCC is very satisfactory in the sense that it includes the microscopic properties of the projectile in a reaction model. Well above the Coulomb barrier, the cross sections are in a good agreement with the data. The reasons for the discrepancy between the data and the calculated cross sections at the lower energies, which is also observed in a traditional CDCC, are unclear. [ABSTRACT FROM AUTHOR]

We study the effects of the coupling to the first 2+12C excited state on the elastic scattering and capture reaction for the α + 12C system. The flux absorption from the elastic channel to the capture reaction is simulated by a tiny imaginary part included in the optical potential. Our analyses show that the effect of the coupling is quite significant even at energies below the threshold of the inelastic channel. We also study the behavior of the polarization potential as a function of the energy and angular momentum. [ABSTRACT FROM AUTHOR]

We propose an extension of the continuum discretized coupled channels (CDCC) method, where the projectile is described by a microscopic cluster model. This microscopic generalization (MCDCC) relies only on nucleon-target interactions, and therefore presents an important predictive power. Core excitations can be included without any further parameter. As an example, we investigate the 7Li+208Pb elastic scattering at Elab=27 and 35 MeV. The 7Li nucleus is known to present an α+t cluster structure, and is well described by the resonating group method. An excellent agreement is obtained for the 7Li+208Pb elastic cross sections, provided that breakup channels are properly included. We also present an application to inelastic scattering and discuss future applications of the MCDCC. [ABSTRACT FROM AUTHOR]

d+d (S-wave) elastic scattering phase shifts are studied in an extended microscopic cluster model in order to investigate cluster-breaking effects appearing in the low-energy scattering. The description of the cluster wave function is extended from a simple (0s) harmonic-oscillator shell model to a few-body model, in which the wave function of the sub-system is determined with the Stochastic Variational Method (SVM). To compare the cluster breaking effects with realistic and effective interactions, we employed the G3RS potential as a realistic interaction and the Minnesota (MN) potential as an effective interaction. The calculated phase shifts show that t+p and 3He+n channels are strongly coupled to the d+d channel for the case of the realistic interaction (G3RS). On the contrary, the coupling of these channels plays a relatively minor role for the case of the effective interaction (MN). [ABSTRACT FROM AUTHOR]

The R-matrix method is applied to the Continuum Discretized Coupled Channel (CDCC) approximation. The variational basis is chosen as Lagrange functions, which are shown to be efficient and accurate. We apply the general formalism to the d + 58Ni elastic scattering at Ed = 80 MeV. Future developments are briefly discussed. [ABSTRACT FROM AUTHOR]

A generalized optical potential for elastic scattering induced by light weakly bound nuclei is calculated within the Feshbach projection operator method. The model explicitly takes into account the contribution of the projectile break-up continuum treated within a microscopic cluster model. The model is tested on deuteron and 6Lielastic scattering by different targets at intermediate energies. The optical potentials are then calculated for the 6He(230 MeV)+12Creaction treating the projectile nuclei within two (α + 2n) and three (α + n + n) cluster models. The differences are analyzed. [ABSTRACT FROM AUTHOR]

The 15O(α,α)15O elastic scattering is investigated using a 15O radioactive beam and a He gas cell limited by Mylar windows. The width of a 19Ne state at an excitation energy of 5.35MeV is measured as Γα = 3.2±1.6keV, in agreement with charge symmetry estimate. [ABSTRACT FROM AUTHOR]

We use microscopic 9Be wave functions defined in a α+α+n multicluster model to compute 9Be+target scattering cross sections. The parameter sets describing 9Be are generated in the spirit of the stochastic variational method, and the optimal solution is obtained by superposing Slater determinants and by diagonalizing the Hamiltonian. The 9Be three-body continuum is approximated by square-integral wave functions. The 9Be microscopic wave functions are then used in a continuum-discretized coupled-channel (CDCC) calculation of 9Be+208Pb and of 9Be+27Al elastic scattering. Without any parameter fitting, we obtain a fair agreement with experiment. For a heavy target, the influence of 9Be breakup is important, while it is weaker for light targets. This result confirms previous nonmicroscopic CDCC calculations. One of the main advantages of the microscopic CDCC is that it is based on nucleon-target interactions only; there is no adjustable parameter. The present work represents a first step towards more ambitious calculations involving heavier Be isotopes. [ABSTRACT FROM AUTHOR]

The 7Be+p elastic cross section has been measured at the Centre de Recherches du Cyclotron RIB facility at Louvain-la-Neuve in the c.m. energy region from 0.3 to 0.75 MeV by bombarding a proton-rich target with a radioactive 7Be beam. The recoil protons have been detected in the angular range θc.m.=120.2°–131.1° and θc.m.=156.6°–170.2° using the LEDA system. From a R-matrix analysis of the cross section data, we obtain the energy and the width of the 1+ resonance (Ex=0.77 MeV). The ℓ=0 scattering lengths a01=25±9 fm (channel spin I=1) and a02=−7±3 fm (channel spin I=2) have been deduced. They are compared to values expected from charge-symmetry properties. Implications on the low energy S-factor of the 7Be(p, γ)8B reaction are discussed. [Copyright &y& Elsevier]

Abstract: We present an experimental study of 19Na states in the excitation energy range between 2 and 3 MeV. The presence of 19Na single-particle levels at these energies was first predicted by a microscopic cluster model and then experimentally confirmed by measuring the elastic and inelastic scattering of a 66 MeV 18Ne radioactive beam on a (CH2) n target. The H(18Ne, p)18Ne(g.s.) and H(18Ne, )18Ne*() cross sections have been obtained in the laboratory angular range and analyzed by using the R-matrix method. Two new states in 19Na have been observed at centre-of-mass energies and . Both resonances exhibit large widths in the channel, and low branching ratios into the elastic channel. The reduced proton widths confirm the single-particle nature of these states, with a structure. [Copyright &y& Elsevier]

Abstract: The RIBRAS facility (Radioactive Ion Beams in Brasil) is installed in connection with the 8MV Pelletron tandem of the University of São Paulo Physics Institute. It consists of two superconducting solenoids which focalize light radioactive secondary beams of low energy, produced by transfer reactions. Recent experimental results include the elastic scattering and transfer reactions of 6He halo nucleus on 9Be, 27Al, 51V and 120Sn targets. The elastic scattering and transfer of 8Li and 7Be on several targets is also being studied. The transfer reaction 8Li(p,α)5He of astrophysical interest was also studied in the energy range. [Copyright &y& Elsevier]