Interaction of 8 He with 208Pb at near-barrier energies: 4 He and 6 He production

Spanish Ministry of Economy and Competitiveness-FPA-2010-22131-CO2-01 (FINURA) y FPA2013-47327-C2-1-RMinistry of Science and Higher Education of Poland-N202 033637National Science Centre of Poland-2013/08/M/ST2/00257 (LEA-COPIGAL) y 2014/14/M/ST2/00738 (COPIN-INFN Collaboration)European Science Foundation-EUI2009-04163432 (EUROGENESIS

Nuclear astrophysics with radioactive ions at FAIR

The nucleosynthesis of elements beyond iron is dominated by neutron captures in the s and r processes. However, 32 stable, proton-rich isotopes cannot be formed during those processes, because they are shielded from the s-process ow and r-process -decay chains. These nuclei are attributed to the p and rp process. For all those processes, current research in nuclear astrophysics addresses the need for more precise reaction data involving radioactive isotopes. Depending on the particular reaction, direct or inverse kinematics, forward or time-reversed direction are investigated to determine or at least to constrain the desired reaction cross sections. The Facility for Antiproton and Ion Research (FAIR) will o er unique, unprecedented opportunities to investigate many of the important reactions. The high yield of radioactive isotopes, even far away from the valley of stability, allows the investigation of isotopes involved in processes as exotic as the r or rp processes

Study of the near-barrier scattering of 8 He on 208 Pb

The structure and dynamics of 8He have been studied through the collision process with a 208 Pb target at energies of 22 and 16 MeV, above and below the Coulomb barrier, respectively. The energy and angular distributions of the elastically scattered 8He and the 6,4He fragments were measured. In this paper, we discuss the method used to determine the effective position of the beam spot on the reaction target and the scattering and solid angles of each pixel of the detector array.Ministerio de Economía y Competitividad PA2010-22131-C021-01, FPA2014-59954-C3-1-PMinistry of Science and Higher Education of Poland N202 03363European Science Foundation EUI2009-0416

Elastic scattering of 8He + 208Pb at 22MeV

The dynamics of 8He around the Coulomb barrier is investigated by measuring the energy and angular distribution of the elastic 8He and the 6He and 4He fragment yields in the collision process with a 208Pb target. The experiment was carried out at SPIRAL/GANIL in October 2010. The experimental results will provide information about the relevant reaction mechanisms and the validity of the optical model (OM) when applied to exotic nuclei. In this paper, details of the experimental setup and preliminary results on the elastic scattering for the collision at 22 MeV are presented.Spanish Research Council FPA-2010-22131-CO2-01Ministry of Science and Higher Education of Poland N202 03363

Scattering of 8He on 208Pb at Energies Around the Coulomb Barrier

We have measured the angular distributions of elastic scattering and 6,4He fragments produced in the collisions of an exotic beam of 8He on a 208Pb target at laboratory energies of 18 and 22 MeV, just around the Coulomb barrier (19 MeV). The measurements were performed at the SPIRAL/GANIL facility in Caen, France. In this paper, we present preliminary data on elastic cross sections and discuss the results using optical model and coupled reaction channel calculations.Spanish Research Council FPA-2010-22131-C02-01Ministry of Science and Higher Education of Poland No. N202 03363

Fusion of 8He with 206Pb around Coulomb barrier energies

The experimental study of the fusion of light neutron-rich nucleus 8He with 206Pb is reported in this work. A fusion stack of 206Pb targets has been used for this study. The most prominent evaporation residue (210Po), which has half-life of 138 days and decays by alpha emission, is populated in the reaction. Radiochemical analysis technique is used to extract the yield of this evaporation residue.Ministerio de Ciencia e Innovavión FPA2007-63074European Union 21269

Interaction of 8He with 208Pb at near-barrier energies: 4He and 6He production

Angular distributions for the inclusive 4He and 6He production cross sections in the 8He+208Pb system at incident energies of 16 and 22 MeV measured at the SPIRAL facility of the GANIL laboratory are presented. Using a combination of kinematical arguments and distorted wave Born approximation (DWBA) calculations, neutron transfer reactions were inferred to be the dominant contributors to both inclusive cross sections. Model-dependent values for the ratios of two- to one-neutron stripping, s2n/s1n, were derived and compared with previous results for 8He and 6He projectiles incident on other heavy targets. Three- and four-neutron stripping were inferred to be the main processes leading to 4He production, although the exact mechanism remains to be elucidated.The authors would like to thank the staff of the GANIL accelerator facility for providing the high-quality 8He beam. This work was supported in part by Grants No. FPA-2010-22131-CO2-01 (FINURA) and No. FPA2013-47327-C2-1-R from the Spanish Ministry of Economy and Competitiveness, UNAM-PAPIIT IA103218 (Mexico); Grant No. N202 033637 from the Ministry of Science and Higher Education of Poland; the National Science Centre of Poland under Contracts No. 2013/08/M/ST2/00257 (LEA-COPIGAL) and No. 2014/14/M/ST2/00738 (COPIN-INFN Collaboration); and Grant No. EUI2009-04163432 (EUROGENESIS) from the European Science Foundation

Sub-barrier fusion of 6He with 206Pb

Cross-sections for the production of 210Po nuclei in 6He + 206Pb collisions over the incident energy range 14–18MeV were measured by means of the activation technique and a radiochemical analysis. The elastic scattering at 18.0MeV was also measured providing a precise value for the 210Po production cross-section at this energy. The results are at variance with the earlier experimental data and rather in accord with the predictions of a density-dependent barrier penetration model for the fusion process. A proper treatment of beam energy distribution for the evaluation of the activation data is discussed

Breakup and neutron-transfer effects on 6He+206Pb elastic scattering below the Coulomb barrier

The elastic scattering and inclusive α-particle yield for the 6He + 206Pb system at an incident energy of 18 MeV, just below the nominal Coulomb barrier, have been measured. The α-particle yield at forward angles is also reported. The data are analyzed by means of continuum-discretized coupled-channels, distorted wave Born approximation, and coupled reaction channels calculations. Couplings to the one-neutron- and two-neutron-transfer reactions are found to be able to account for most of the absorption in the entrance channel.This work was supported in part by Grant No. FPA2010-22131-C02-01 from the Spanish Ministry of Science

Scattering of 8He on 208Pb at 22 MeV

The skin nucleus 8He is investigated by measuring the angular distribution of the elasticly scattered 8He and the 6,4He fragments produced in the collision with a 208Pb target at 22 MeV, just above the Coulomb barrier. The experiment was carried out at SPIRAL/GANIL in 2010. Here we present preliminary results for the elastic scattering