V. Guimarães | Universidade de São Paulo (original) (raw)
Papers by V. Guimarães
Journal of Physics: Conference Series
The resonant scattering of 10B+p reaction was measured at θ c.m.= 180°, 170°, 160°, 150° and 140°... more The resonant scattering of 10B+p reaction was measured at θ c.m.= 180°, 170°, 160°, 150° and 140° using a 35.93 MeV 10B beam to investigate the spectroscopy of 11C with the thick target inverse kinematic method at RIBRAS facility, IFUSP, São Paulo. Influence of the stopping power uncertainty on the resonant scattering cross section values for 11C in the 10B(p, p)10B reaction is shown. The data measured for the reaction channels p(10B,α) and p(10B,3He) is also presented. Interestingly, the cross sections for the 3He channel are observed upto 2 MeV below the lowest energy measurement available in literature.
Physical Review C, 2021
The 8 Li + 58 Ni collision is investigated at 23.9, 26.1, 28.7, and 30 MeV bombarding energies. Q... more The 8 Li + 58 Ni collision is investigated at 23.9, 26.1, 28.7, and 30 MeV bombarding energies. Quasielastic angular distributions and the singles 7 Li angular and energy distributions are presented. Coupled-reaction channels (CRC) calculations, which include the coupling of the elastic channel to 59 Ni = 58 Ni + n states above and below the neutron threshold, provide a simultaneous description of the quasielastic and transfer distributions and evidence the strong effect of the one-neutron transfer/breakup channels on the quasielastic scattering. The 7 Li angular and energy distributions have been also successfully analyzed combining the continuum discretized coupled channels (CDCC) method, for the elastic breakup, and the IAV model of Ichimura, Austern, and Vincent [Phys. Rev. C 32, 431 (1985)], for the nonelastic breakup. These calculations indicate that most of the 7 Li yields are due to nonelastic breakup contributions (transfer), whereas elastic breakup plays a minor role.
Physical Review C, 2021
Spatially-correlated overabundances of 15^{15}15N and 18^{18}18O observed in some low-density graphit... more Spatially-correlated overabundances of 15^{15}15N and 18^{18}18O observed in some low-density graphite meteoritic grains have been connected to nucleosynthesis taking place in the helium-burning shell during core-collapse supernovae. Two of the reactions which have been identified as important to the final abundances of 15^{15}15N and 18^{18}18O are 18^{18}18F($n,\alpha$)$^{15}$N and 18^{18}18F($n,p$)$^{18}$O. The relative strengths of the 18^{18}18F($n,\alpha$)$^{15}$N and 18^{18}18F($n,p$)$^{18}$O reactions depend on the relative alpha_0\alpha_0alpha0 and p0p_0p_0 decays from states above the neutron threshold in 19^{19}19F in addition to other properties. Experimental data on the charged-particle decays from these highly excited states are lacking or inconsistent. Two experiments were performed using proton inelastic scattering from LiF targets and magnetic spectrographs. The first experiment used the high-resolution Q3D spectrograph at Munich to constrain properties of levels in 19^{19}19F. A second experiment u...
The elastic scattering of the radioactive halo nucleus He on Al target was measured at four energ... more The elastic scattering of the radioactive halo nucleus He on Al target was measured at four energies close to the Coulomb barrier using the RIBRAS (Radioactive Ion Beams in Brazil) facility. The São Paulo Potential (SPP) was used and its diffuseness and imaginary strength were adjusted to fit the elastic scattering angular distributions. Reaction cross-sections were extracted from the optical model fits. The reduced reaction cross-sections of He on Al are similar to those for stable, weakly bound projectiles as Li, Be and larger than stable, tightly bound projectile as O on Al. Reactions induced by halo nuclei are currently one of the main subjects in Nuclear Physics, with interest in nuclear structure, reactions, astrophysics and production of superheavy elements. Nowadays reliable measurements of elastic, inelastic and transfer cross sections of unstable projectiles are possible due to new Radioactive Nuclear Beam (RNB) facilities. Nuclei that have small separation energies have l...
Physics Letters B, 2020
Angular distributions of quasielastic scattering and breakup of the neutron-rich halo nucleus 11 ... more Angular distributions of quasielastic scattering and breakup of the neutron-rich halo nucleus 11 Be on a 208 Pb target at an incident energy of 140 MeV (about 3.5 times the Coulomb barrier) were measured at HIRFL-RIBLL. A strong suppression of the Coulomb nuclear interference peak is observed in the measured quasielastic scattering angular distribution. The result demonstrates for the first time the persistence of the strong breakup coupling effect reported so far for reaction systems involving neutron-halo nuclei at this relatively high incident energy. The measured quasielastic scattering cross sections are satisfactorily reproduced by continuum discretized coupled channel (CDCC) calculations as well as by the XCDCC calculations where the deformation of the 10 Be core is taken into account. The angular and energy distributions of the 10 Be fragments could also be well reproduced considering elastic breakup (CDCC and XCDCC) plus nonelastic breakup contributions, with the latter evaluated with the model by Ichimura, Austern and Vincent [1]. The comparison of the 10 Be energy distributions with simple kinematical estimates evidence the presence of a significant post-acceleration effect which, in the (X)CDCC frameworks, is accounted for by continuum-continuum couplings.
Physical Review C, 2019
The elastic scattering of the radioactive proton-rich carbon isotope, 10 C, has been investigated... more The elastic scattering of the radioactive proton-rich carbon isotope, 10 C, has been investigated. A full differential angular distribution for the elastic scattering of 10 C on a 58 Ni target has been measured at E Lab = 35.3 MeV, which is just above the Coulomb Barrier for this system (V B = 27 MeV). The obtained angular distribution was analyzed in terms of coupled channel (CC), coupled reaction channel (CRC) and continuum discretized coupled channel (CDCC) calculations. In the coupled-channel calculation, several inelastic transitions of the target and the first (2 +) excited state of the 10 C projectile were considered. The coupling to the first (2 +) excited state of 10 C was shown to be very important to describe the rising of the cross section at backward angles. We also performed an analysis with the continuum discretized coupled channels, considering the 9 B+p and 6 Be+α channels, which indicated a strong cluster configuration for the 10 C projectile.
Journal of Physics: Conference Series, 2019
In this work we present an elastic scattering angular distribution for the 8Li+58Ni system measur... more In this work we present an elastic scattering angular distribution for the 8Li+58Ni system measured at Elab = 26.1 MeV. The 8Li beam was produced in the Radioactive Ion Beams in Brasil (RIBRAS) facility using the 7Li primary beam delivered by the 8-UD Pelletron accelerator. The angular distribution covers the angular range from 20 to 85 degrees in the center of mass frame. The data have been analysed by optical model and coupled channels calculations, including couplings to low-lying states in 8Li and the spin-orbit interaction. Our results indicate that the inclusion of the spin-orbit interaction in the calculations is important to describe the data at backward angles.
Physical Review C, 2019
Elastic scattering and transfer cross sections for the 7 Be + 9 Be system have been measured at E... more 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.
![Research paper thumbnail of Erratum: The Li8(p,α)He5 reaction at low energies, and Be9 spectroscopy around the proton threshold [Phys. Rev. C 86 , 064321 (2012)]](https://attachments.academia-assets.com/95912343/thumbnails/1.jpg)
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Physical Review C, 2017
Evaporation-proton yields were measured for the fusion of the weakly-bound nucleus 6 Li on a 58 N... more Evaporation-proton yields were measured for the fusion of the weakly-bound nucleus 6 Li on a 58 Ni target at six near-or sub-barrier bombarding energies. Effects of the one-neutron transfer reaction were estimated and corrections made. Total-fusion cross sections were deduced using calculated proton multiplicities. The resulting fusion excitation function shows a considerable enhancement with respect to calculations for a bare potential. Inelastic couplings are estimated to have insignificant effects on such fusion. The sum of total fusion plus one-neutron transfer cross sections nearly saturates the total reaction cross section in the energy region measured. Comparison with previous results appropriately scaled for the 6 Li + (59 Co, 64 Ni, 64 Zn) systems shows good consistency except for some data spread at the lower energies.
AIP Conference Proceedings, 2007
A systematic for the light proton rich nuclei with constant TZ = -3/2 isospin is proposed, where ... more A systematic for the light proton rich nuclei with constant TZ = -3/2 isospin is proposed, where a survey on their structure have shown interesting features. Preliminary results of a re-analysis on the sctructure of 13O nucleus is also presented. This 13O nucleus have been investigated by the 3-neutron pick up (3He,6He) reaction, and new levels have been assigned for this nucleus.
European Physical Journal Plus, 2013
Cross-sections for fragments produced by the fission reaction induced by accelerated 7 Li ions im... more Cross-sections for fragments produced by the fission reaction induced by accelerated 7 Li ions impinged into an nat Pb target at 245 MeV were obtained. We have applied the induced-activation method in off-line analysis. The analysis of charge and mass distributions of fission products allowed the determination of the total fission cross-section for the 7 Li+Pb system. The recoil technique ("thick target-thick catcher"), based on the two step model mathematical formalism, is used to determine the kinematics characteristics of reaction products. Analysis concerning transferred linear momentum provided information on the initial projectile-target interaction, and is compared with proton-induced fission measurements.
AIP Conference Proceedings, 2009
The cluster structure of 7Li and 7Be has been investigated by the elastic-transfer 4He(7Li,4He)7L... more The cluster structure of 7Li and 7Be has been investigated by the elastic-transfer 4He(7Li,4He)7Li and 3He(7Be,3He)7Be reactions, respectively. Angular distribution for the elastic-transfer of 7Li+4He has been measured in Sao Paulo at ECM = 9.67 MeV. Together with available elastic-transfer angular distributions measured at other energies ranging from ECM = 2.29 to 32.13 MeV, a global optical model analysis has
AIP Conference Proceedings, 2011
We present the results of the 8Li(p,α)5He transfer reaction, measured at the RIBRAS facility. It ... more We present the results of the 8Li(p,α)5He transfer reaction, measured at the RIBRAS facility. It was performed in inverse kinematics using a thick CH2 polyethylene target. The complete excitation function was measured between Ecm = 0.4–2.7 MeV, which includes the Gamow peak energy region. The excitation function was reproduced with the R-matrix theory.
Physical Review Letters, 2011
Fusion cross sections were measured for the exotic proton-halo nucleus 8 B incident on a 58 Ni ta... more Fusion cross sections were measured for the exotic proton-halo nucleus 8 B incident on a 58 Ni target at several energies near the Coulomb barrier. This is the first experiment to report on the fusion of a proton-halo nucleus. The resulting excitation function shows a striking enhancement with respect to expectations for normal projectiles. Evidence is presented that the sum of the fusion and breakup yields saturates the total reaction cross section.
Physical Review C, 2007
Angular distributions for the elastic scattering of 8 Li on 9 Be and the neutron transfer reactio... more Angular distributions for the elastic scattering of 8 Li on 9 Be and the neutron transfer reactions 9 Be(8 Li, 7 Li) 10 Be and 9 Be(8 Li, 9 Li) 8 Be have been measured with a 27 MeV 8 Li radioactive nuclear beam. Spectroscopic factors for 8 Li⊗n= 9 Li and 7 Li⊗n= 8 Li bound systems were obtained from the comparison between the experimental differential cross section and finite-range DWBA calculations with the code FRESCO. The spectroscopic factors obtained are compared to shell model calculations and to other experimental values from (d,p) reactions. Using the present values for the spectroscopic factor, cross sections for the direct neutron-capture reactions 7 Li(n,γ) 8 Li and 8 Li(n,γ) 9 Li were calculated in the framework of a potential model.
Physical Review C, 2004
Full Coupled Channels Calculations were performed for the 16 O(d, n) 17 F and 16 O(d, p) 17 O tra... more 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.
Physical Review C, 2001
Energy distributions for outgoing 7 Be fragments from breakup of 8 B on a 58 Ni target have been ... more Energy distributions for outgoing 7 Be fragments from breakup of 8 B on a 58 Ni target have been measured at an incident energy of 25.75 MeV, which is below the Coulomb barrier. The data are compared with coupled-channels calculations that include higher-order couplings in the continuum.
Brazilian Journal of Physics, 2004
Spectroscopic investigation, on exotic nuclei, performed in two different experiments with second... more Spectroscopic investigation, on exotic nuclei, performed in two different experiments with secondary radioactive boron beams are discussed. Spectroscopic factors for the 13 B+n bound-states are obtained by measuring momentum distribution of the 13 B residual nucleus from knockout reaction of the 14 B beam at intermediate energy. The momentum distributions are measured in coincidence with the emited γ-rays from the excited residual 13 B nucleus allowing spin-parity assignment and partial cross section determination. In the other experiment, a deuteron transfer, 2 H(8 B,α) 6 Be, reaction with low energy 8 B beam are used to search for resonances in the unbound 6 Be nucleus. The ANC-Asymptotic Normalization Coefficient method are presented and astrophysical implications of these two experiments are discussed.
Brazilian Journal of Physics, 2004
The spectroscopic study of unbound states in the 6 Li nucleus was performed by measuring the ener... more The spectroscopic study of unbound states in the 6 Li nucleus was performed by measuring the energy spectrum of the α-particles emitted from the transfer reaction 3 He(7 Li, α) 6 Li. The 7 Li beam at E Lab = 31.2M eV was produced at the São Paulo Pelletron accelerator. A 3 He gas cell was used as target. α-Particle spectra were measured from θ Lab = 8 • up to θ Lab = 20 • with steps of 1 •. Due to its positive Q = +13.3M eV , the 3 He(7 Li, α) 6 Li reaction favours the population of states in 6 Li at high excitations energies up to about 20M eV. We observed resonances at 17.29M eV , 15.31M eV , and a new state at 12.45M eV , in addition to all previously known states of 6 Li. An-Matrix analysis was performed and the positions and widths of these states were extracted.
Journal of Physics: Conference Series
The resonant scattering of 10B+p reaction was measured at θ c.m.= 180°, 170°, 160°, 150° and 140°... more The resonant scattering of 10B+p reaction was measured at θ c.m.= 180°, 170°, 160°, 150° and 140° using a 35.93 MeV 10B beam to investigate the spectroscopy of 11C with the thick target inverse kinematic method at RIBRAS facility, IFUSP, São Paulo. Influence of the stopping power uncertainty on the resonant scattering cross section values for 11C in the 10B(p, p)10B reaction is shown. The data measured for the reaction channels p(10B,α) and p(10B,3He) is also presented. Interestingly, the cross sections for the 3He channel are observed upto 2 MeV below the lowest energy measurement available in literature.
Physical Review C, 2021
The 8 Li + 58 Ni collision is investigated at 23.9, 26.1, 28.7, and 30 MeV bombarding energies. Q... more The 8 Li + 58 Ni collision is investigated at 23.9, 26.1, 28.7, and 30 MeV bombarding energies. Quasielastic angular distributions and the singles 7 Li angular and energy distributions are presented. Coupled-reaction channels (CRC) calculations, which include the coupling of the elastic channel to 59 Ni = 58 Ni + n states above and below the neutron threshold, provide a simultaneous description of the quasielastic and transfer distributions and evidence the strong effect of the one-neutron transfer/breakup channels on the quasielastic scattering. The 7 Li angular and energy distributions have been also successfully analyzed combining the continuum discretized coupled channels (CDCC) method, for the elastic breakup, and the IAV model of Ichimura, Austern, and Vincent [Phys. Rev. C 32, 431 (1985)], for the nonelastic breakup. These calculations indicate that most of the 7 Li yields are due to nonelastic breakup contributions (transfer), whereas elastic breakup plays a minor role.
Physical Review C, 2021
Spatially-correlated overabundances of 15^{15}15N and 18^{18}18O observed in some low-density graphit... more Spatially-correlated overabundances of 15^{15}15N and 18^{18}18O observed in some low-density graphite meteoritic grains have been connected to nucleosynthesis taking place in the helium-burning shell during core-collapse supernovae. Two of the reactions which have been identified as important to the final abundances of 15^{15}15N and 18^{18}18O are 18^{18}18F($n,\alpha$)$^{15}$N and 18^{18}18F($n,p$)$^{18}$O. The relative strengths of the 18^{18}18F($n,\alpha$)$^{15}$N and 18^{18}18F($n,p$)$^{18}$O reactions depend on the relative alpha_0\alpha_0alpha0 and p0p_0p_0 decays from states above the neutron threshold in 19^{19}19F in addition to other properties. Experimental data on the charged-particle decays from these highly excited states are lacking or inconsistent. Two experiments were performed using proton inelastic scattering from LiF targets and magnetic spectrographs. The first experiment used the high-resolution Q3D spectrograph at Munich to constrain properties of levels in 19^{19}19F. A second experiment u...
The elastic scattering of the radioactive halo nucleus He on Al target was measured at four energ... more The elastic scattering of the radioactive halo nucleus He on Al target was measured at four energies close to the Coulomb barrier using the RIBRAS (Radioactive Ion Beams in Brazil) facility. The São Paulo Potential (SPP) was used and its diffuseness and imaginary strength were adjusted to fit the elastic scattering angular distributions. Reaction cross-sections were extracted from the optical model fits. The reduced reaction cross-sections of He on Al are similar to those for stable, weakly bound projectiles as Li, Be and larger than stable, tightly bound projectile as O on Al. Reactions induced by halo nuclei are currently one of the main subjects in Nuclear Physics, with interest in nuclear structure, reactions, astrophysics and production of superheavy elements. Nowadays reliable measurements of elastic, inelastic and transfer cross sections of unstable projectiles are possible due to new Radioactive Nuclear Beam (RNB) facilities. Nuclei that have small separation energies have l...
Physics Letters B, 2020
Angular distributions of quasielastic scattering and breakup of the neutron-rich halo nucleus 11 ... more Angular distributions of quasielastic scattering and breakup of the neutron-rich halo nucleus 11 Be on a 208 Pb target at an incident energy of 140 MeV (about 3.5 times the Coulomb barrier) were measured at HIRFL-RIBLL. A strong suppression of the Coulomb nuclear interference peak is observed in the measured quasielastic scattering angular distribution. The result demonstrates for the first time the persistence of the strong breakup coupling effect reported so far for reaction systems involving neutron-halo nuclei at this relatively high incident energy. The measured quasielastic scattering cross sections are satisfactorily reproduced by continuum discretized coupled channel (CDCC) calculations as well as by the XCDCC calculations where the deformation of the 10 Be core is taken into account. The angular and energy distributions of the 10 Be fragments could also be well reproduced considering elastic breakup (CDCC and XCDCC) plus nonelastic breakup contributions, with the latter evaluated with the model by Ichimura, Austern and Vincent [1]. The comparison of the 10 Be energy distributions with simple kinematical estimates evidence the presence of a significant post-acceleration effect which, in the (X)CDCC frameworks, is accounted for by continuum-continuum couplings.
Physical Review C, 2019
The elastic scattering of the radioactive proton-rich carbon isotope, 10 C, has been investigated... more The elastic scattering of the radioactive proton-rich carbon isotope, 10 C, has been investigated. A full differential angular distribution for the elastic scattering of 10 C on a 58 Ni target has been measured at E Lab = 35.3 MeV, which is just above the Coulomb Barrier for this system (V B = 27 MeV). The obtained angular distribution was analyzed in terms of coupled channel (CC), coupled reaction channel (CRC) and continuum discretized coupled channel (CDCC) calculations. In the coupled-channel calculation, several inelastic transitions of the target and the first (2 +) excited state of the 10 C projectile were considered. The coupling to the first (2 +) excited state of 10 C was shown to be very important to describe the rising of the cross section at backward angles. We also performed an analysis with the continuum discretized coupled channels, considering the 9 B+p and 6 Be+α channels, which indicated a strong cluster configuration for the 10 C projectile.
Journal of Physics: Conference Series, 2019
In this work we present an elastic scattering angular distribution for the 8Li+58Ni system measur... more In this work we present an elastic scattering angular distribution for the 8Li+58Ni system measured at Elab = 26.1 MeV. The 8Li beam was produced in the Radioactive Ion Beams in Brasil (RIBRAS) facility using the 7Li primary beam delivered by the 8-UD Pelletron accelerator. The angular distribution covers the angular range from 20 to 85 degrees in the center of mass frame. The data have been analysed by optical model and coupled channels calculations, including couplings to low-lying states in 8Li and the spin-orbit interaction. Our results indicate that the inclusion of the spin-orbit interaction in the calculations is important to describe the data at backward angles.
Physical Review C, 2019
Elastic scattering and transfer cross sections for the 7 Be + 9 Be system have been measured at E... more 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.
Physical Review C, 2017
Evaporation-proton yields were measured for the fusion of the weakly-bound nucleus 6 Li on a 58 N... more Evaporation-proton yields were measured for the fusion of the weakly-bound nucleus 6 Li on a 58 Ni target at six near-or sub-barrier bombarding energies. Effects of the one-neutron transfer reaction were estimated and corrections made. Total-fusion cross sections were deduced using calculated proton multiplicities. The resulting fusion excitation function shows a considerable enhancement with respect to calculations for a bare potential. Inelastic couplings are estimated to have insignificant effects on such fusion. The sum of total fusion plus one-neutron transfer cross sections nearly saturates the total reaction cross section in the energy region measured. Comparison with previous results appropriately scaled for the 6 Li + (59 Co, 64 Ni, 64 Zn) systems shows good consistency except for some data spread at the lower energies.
AIP Conference Proceedings, 2007
A systematic for the light proton rich nuclei with constant TZ = -3/2 isospin is proposed, where ... more A systematic for the light proton rich nuclei with constant TZ = -3/2 isospin is proposed, where a survey on their structure have shown interesting features. Preliminary results of a re-analysis on the sctructure of 13O nucleus is also presented. This 13O nucleus have been investigated by the 3-neutron pick up (3He,6He) reaction, and new levels have been assigned for this nucleus.
European Physical Journal Plus, 2013
Cross-sections for fragments produced by the fission reaction induced by accelerated 7 Li ions im... more Cross-sections for fragments produced by the fission reaction induced by accelerated 7 Li ions impinged into an nat Pb target at 245 MeV were obtained. We have applied the induced-activation method in off-line analysis. The analysis of charge and mass distributions of fission products allowed the determination of the total fission cross-section for the 7 Li+Pb system. The recoil technique ("thick target-thick catcher"), based on the two step model mathematical formalism, is used to determine the kinematics characteristics of reaction products. Analysis concerning transferred linear momentum provided information on the initial projectile-target interaction, and is compared with proton-induced fission measurements.
AIP Conference Proceedings, 2009
The cluster structure of 7Li and 7Be has been investigated by the elastic-transfer 4He(7Li,4He)7L... more The cluster structure of 7Li and 7Be has been investigated by the elastic-transfer 4He(7Li,4He)7Li and 3He(7Be,3He)7Be reactions, respectively. Angular distribution for the elastic-transfer of 7Li+4He has been measured in Sao Paulo at ECM = 9.67 MeV. Together with available elastic-transfer angular distributions measured at other energies ranging from ECM = 2.29 to 32.13 MeV, a global optical model analysis has
AIP Conference Proceedings, 2011
We present the results of the 8Li(p,α)5He transfer reaction, measured at the RIBRAS facility. It ... more We present the results of the 8Li(p,α)5He transfer reaction, measured at the RIBRAS facility. It was performed in inverse kinematics using a thick CH2 polyethylene target. The complete excitation function was measured between Ecm = 0.4–2.7 MeV, which includes the Gamow peak energy region. The excitation function was reproduced with the R-matrix theory.
Physical Review Letters, 2011
Fusion cross sections were measured for the exotic proton-halo nucleus 8 B incident on a 58 Ni ta... more Fusion cross sections were measured for the exotic proton-halo nucleus 8 B incident on a 58 Ni target at several energies near the Coulomb barrier. This is the first experiment to report on the fusion of a proton-halo nucleus. The resulting excitation function shows a striking enhancement with respect to expectations for normal projectiles. Evidence is presented that the sum of the fusion and breakup yields saturates the total reaction cross section.
Physical Review C, 2007
Angular distributions for the elastic scattering of 8 Li on 9 Be and the neutron transfer reactio... more Angular distributions for the elastic scattering of 8 Li on 9 Be and the neutron transfer reactions 9 Be(8 Li, 7 Li) 10 Be and 9 Be(8 Li, 9 Li) 8 Be have been measured with a 27 MeV 8 Li radioactive nuclear beam. Spectroscopic factors for 8 Li⊗n= 9 Li and 7 Li⊗n= 8 Li bound systems were obtained from the comparison between the experimental differential cross section and finite-range DWBA calculations with the code FRESCO. The spectroscopic factors obtained are compared to shell model calculations and to other experimental values from (d,p) reactions. Using the present values for the spectroscopic factor, cross sections for the direct neutron-capture reactions 7 Li(n,γ) 8 Li and 8 Li(n,γ) 9 Li were calculated in the framework of a potential model.
Physical Review C, 2004
Full Coupled Channels Calculations were performed for the 16 O(d, n) 17 F and 16 O(d, p) 17 O tra... more 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.
Physical Review C, 2001
Energy distributions for outgoing 7 Be fragments from breakup of 8 B on a 58 Ni target have been ... more Energy distributions for outgoing 7 Be fragments from breakup of 8 B on a 58 Ni target have been measured at an incident energy of 25.75 MeV, which is below the Coulomb barrier. The data are compared with coupled-channels calculations that include higher-order couplings in the continuum.
Brazilian Journal of Physics, 2004
Spectroscopic investigation, on exotic nuclei, performed in two different experiments with second... more Spectroscopic investigation, on exotic nuclei, performed in two different experiments with secondary radioactive boron beams are discussed. Spectroscopic factors for the 13 B+n bound-states are obtained by measuring momentum distribution of the 13 B residual nucleus from knockout reaction of the 14 B beam at intermediate energy. The momentum distributions are measured in coincidence with the emited γ-rays from the excited residual 13 B nucleus allowing spin-parity assignment and partial cross section determination. In the other experiment, a deuteron transfer, 2 H(8 B,α) 6 Be, reaction with low energy 8 B beam are used to search for resonances in the unbound 6 Be nucleus. The ANC-Asymptotic Normalization Coefficient method are presented and astrophysical implications of these two experiments are discussed.
Brazilian Journal of Physics, 2004
The spectroscopic study of unbound states in the 6 Li nucleus was performed by measuring the ener... more The spectroscopic study of unbound states in the 6 Li nucleus was performed by measuring the energy spectrum of the α-particles emitted from the transfer reaction 3 He(7 Li, α) 6 Li. The 7 Li beam at E Lab = 31.2M eV was produced at the São Paulo Pelletron accelerator. A 3 He gas cell was used as target. α-Particle spectra were measured from θ Lab = 8 • up to θ Lab = 20 • with steps of 1 •. Due to its positive Q = +13.3M eV , the 3 He(7 Li, α) 6 Li reaction favours the population of states in 6 Li at high excitations energies up to about 20M eV. We observed resonances at 17.29M eV , 15.31M eV , and a new state at 12.45M eV , in addition to all previously known states of 6 Li. An-Matrix analysis was performed and the positions and widths of these states were extracted.