Higher order effects in the 16O(d,p)17O^{16}O(d,p)^{17}O and 16O(d,n)17F^{16}O(d,n)^{17}F transfer reactions

Full Coupled Channels Calculations were performed for the $^{16}O(d,n)^{17}F$ and $^{16}O(d,p)^{17}O$ transfer reactions at several deuteron incident energies from $E_{lab}=2.29$ MeV up to 3.27 MeV. A strong polarization effect between the entrance channel and the transfer channels $^{16}O(d,n)^{17}F(1/2^{+},0.495)$ and $^{16}O(d,p)^{17}O(1/2^{+},0.87)$ was observed. This polarization effect had to be taken into account in order to obtain realistic spectroscopic factors from these reactions.Comment: 15 papes, 13 figures, accepted for publication in Phys. Rev.

Comparison of 120Sn(6He,6He)120Sn and 120Sn(alpha,alpha)120Sn elastic scattering and signatures of the 6He neutron halo in the optical potential

Cross sections of $^{120}$Sn($\alpha$,$\alpha$)$^{120}$Sn elastic scattering have been extracted from the $\alpha$ particle beam contamination of a recent $^{120}$Sn($^6$He,$^6$He)$^{120}$Sn experiment. Both reactions are analyzed using systematic double folding potentials in the real part and smoothly varying Woods-Saxon potentials in the imaginary part. The potential extracted from the $^{120}$Sn($^6$He,$^6$He)$^{120}$Sn data may be used as the basis for the construction of a simple global $^6$He optical potential. The comparison of the $^6$He and $\alpha$ data shows that the halo nature of the $^6$He nucleus leads to a clear signature in the reflexion coefficients $\eta_L$: the relevant angular momenta $L$ with $\eta_L \gg 0$ and $\eta_L \ll 1$ are shifted to larger $L$ with a broader distribution. This signature is not present in the $\alpha$ scattering data and can thus be used as a new criterion for the definition of a halo nucleus.Comment: 13 pages, 7 figures, accepted for publication in Phys. Rev.

The Research Program at RIBRAS (Radioactive Ion Beams in Brasil)-III

A part of the research program developed in the RIBRAS facility over the last four years is presented. Experiments using radioactive secondary beams of light exotic nuclei such as 6He, 7Be, 8Li on several targets have been performed. Elastic angular distributions have been analysed by the Optical Model and four body Continuous Discretized Coupled Channels Calculations (4b-CDCC) and the total reaction cross sections have been obtained. A comparison between the reaction cross sections of 6He and other stable projectiles with medium-heavy targets was performed. Measurements of the proton transfer reaction 12C(8Li,9Be)11B are also presented

Exotic Nuclei in South America

The Radioactive Ion Beams in Brasil (RIBRAS) is described. Experiments using radioactive secondary beams of light rare isotopes such as 6He, 7Be, 8Li on several targets have been performed and the results are presented

Spectroscopy of high-lying resonances in 9 Be by the measurement of ( p , p ), ( p , d ), and ( p , α ) reactions with a radioactive 8 Li beam

We measured the 8 Li ( p , p ) 8 Li , 8 Li ( p , d ) 7 Li , and 8 Li ( p , α ) 5 He reactions at low energies using the thick target inverse kinematics method, with a polyethylene [ CH 2 ] n target and a radioactive 8 Li beam available at the Radioactive Ion Beams in Brazil facility of São Paulo. By measuring simultaneously several reaction channels ( p , p ) , ( p , d ) , and ( p , α ) , the still uncertain high-lying resonances of 9 Be , close to the proton threshold, can be studied and their parameters, such as energy, width, and spin parity can be more reliably determined. The experimental excitation functions of the reactions 8 Li ( p , p ) 8 Li , 8 Li ( p , d ) 7 Li , and 8 Li ( p , α ) 5 He were analyzed using the R -matrix theory, which allows us to infer the properties of the resonances. Multichannel R -matrix analysis provides evidence for a significant clustering in the ( p , d ) channel. The experimental data and the multichannel R -matrix analysis will be presented.Fundação de Amparo à Pesquisa do Estado de São Paulo. Brasil. (FAPESP) 2011/15904-7, 2013/22100-7 y 2016/21434-7VI Plan Propio de Investigación de la Universidad de Sevilla. España. (2017–2018

Measurements of the 25 Mg( 11 B , 12 C) 24 Na and 25 Mg( 11 B , 10 Be) 26 Al proton transfer reactions

Angular distributions for the 11 B+25 Mg elastic scattering, 25 Mg (11B, 12 C) 24 Na proton pickup, and 25 Mg (11 B, 10 Be) 26 Al stripping reactions have been measured at E11 B=35 MeV. The angular distributions have been analyzed by the distorted-waves Born approximation calculations using the code fresco. The spectroscopicfactors for the overlaps 25 Mg | 26 Al , 25 Mg | 24 Na for the ground state and excited states of 26 Al and 24 Na have been obtained and compared to previous measurements and shell-model calculations.FAPESP 01/06676-

Two-neutron transfer in the 6 He + 120 Sn reaction

A large yield of α particles produced in the 120 Sn ( 6 He , α ) reaction was measured at 20.3-, 22.2-, 22.4-, and 24.5-MeV bombarding energies. The α particles are distributed over a broad energy range in the vicinity and below the elastic scattering 6 He peak. Energy integrated α -particle cross sections have been obtained at θ lab = 36 ∘ , 40 ∘ , and 60 ∘ . The α energy distributions have been analyzed at a fixed laboratory angle ( ≈ 60 ∘ ) in terms of the reaction Q value, considering the 2 n -transfer reaction kinematics 120 Sn ( 6 He , α ) 122 Sn . A kinematical analysis of the Q -value distribution shows that the recoil system 120 Sn + 2 n is formed in highly excited states in the continuum, at increasing excitation energies as the bombarding energy increases. It is shown that by using Brink's formula, the excitation energy depends on the transferred angular momentum following a linear relation with the square of the angular momentum, indicating that some kind of dinuclear rotating system is formed after the reaction.Conselho Nacional de Desenvolvimento Científico e Tecnológico-CNPq/MCTI de Brasil y Fundação de Amparo à Pesquisa do Estado de São Paulo. Brasil–FAPESP. 2013/22100-7 y 2014/19666-1VI Plan Propio de Investigación de la Universidad de Sevilla (2017-2018

Two-neutron transfer in 7 Be + 9 Be collisions

Elastic scattering and transfer cross sections for the 7 Be + 9 Be system have been measured at E lab = 23.1 MeV using the 7 Be radioactive secondary beam produced at Radioactive Ion Beams in Brazil facility at the University of São Paulo. The elastic scattering has been measured by detecting the 7 Be scattered at forward angles in the laboratory system. The transfer reaction 9 Be ( 7 Be , 9 Be ) 7 Be was identified by detecting the 9 Be scattered at the same laboratory angles. The elastic angular distribution has been analyzed by optical model calculations using a Woods-Saxon form factor whose parameters have been varied to best reproduce the experimental data at forward angles. Coupled reaction channels calculations (CRC) have been performed to describe the transfer, considering the coupling to the transfer channel and including contributions to the ground state and to the first excited state of 7 Be ( 1 / 2 − ; 429 keV ) in the final state. The spectroscopic amplitudes used in the CRC calculation have been derived from shell-model calculations. Similar CRC calculations were applied to existing 9 Be ( p , t ) 7 Be data to check the consistency of our results results for the ( 7 Be , 9 Be ) transfer reaction.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) de Brasil, Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) de Brasil y Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) de Brasil. 2013/22100-7 y 2016/21434-

Elastic scattering and total reaction cross sections for the 8Li + 12C system

The elastic-scattering angular distribution for 8Li on 12C has been measured at ELAB=23.9 MeV with 8Li radioactive nuclear beam produced by the Radioactive Ion Beams in Brazil facility. This angular distribution was analyzed in terms of optical-model with Woods-Saxon and double-folding São Paulo potential. The roles of the breakup and inelastic channels were also investigated with cluster folding and deformed potentials, respectively, through coupled-channels calculations. The angular distribution for the proton-transfer 12C(8Li,9Be)11B reaction was also measured at the same energy. The spectroscopic factor for the 9Be|8Li+p bound system was obtained and compared with shell-model calculations and with other experimental values. Total reaction cross sections for the present system were also extracted from the elastic-scattering analysis. A systematic of the reduced reaction cross sections obtained from the present and published data on 6,7,8Li isotopes on 12C was performed as a function of energy