Elastic scattering of Beryllium isotopes near the Coulomb barrier

In this contribution, results of experiments performed with the three Beryllium isotopes 9,10,11Be on a medium mass 64Zn target, at a center of mass energy of≈1.4 the Coulomb barrier, will be discussed. Elastic scattering angular distributions have been measured for the 9,10Be reactions. In the 11Be case the quasielastic scattering angular distribution was obtained. In the halo nucleus case, the angular distribution exhibit a non-Fresnel-type pattern with a strong damping of the Coulombnuclear interference peak. Moreover, it is found that the total reaction cross-section for the halo nucleus induced collision is more than double the ones extracted in the collisions induced by the non-halo Beryllium isotopes. A large contribution to the total-reaction cross-section in the 11Be case could be attributed to transfer and/or break-up events

Reaction studies with low-energy weakly-bound beams at INFN-LNS

The reaction dynamics of collisions involving halo or weakly bound nuclei, at energies around the Coulomb barrier, can be strongly affected by the structure of such nuclei. Very strong entrance channel effects have been observed on various reaction pocess such as, elastic scattering, fusion and direct reactions when comparing collision induced by the 6He and 11Be halo nuclei with the ones induced by their cores 4He and 10Be. Collisions induced by the stable weakly bound nuclei 6Li, 7Li show also some peculiarities in comparison to the ones induced by well bound nuclei; coupling with the break-up channel is in fact very important in reproducing low energy data. In this contribution an overview of our present understanding of the discussed topic will be given along with the discussion of some new preliminary results

Effects of coupling to breakup channels in reactions induced by weakly bound and halo nuclei

12th International Conference on Nucleus-Nucleus Collisions 2015The experimental elastic scattering angular distributions of the collisions involving the weakly bound nuclei 6,7Li and the halo nucleus 6He on the same 64Zn target at several energies around the Coulomb barrier were measured at the Laboratori Nazionali del Sud (LNS, Italy), and the Cyclotron Research Center, Louvain La Neuve (Belgium), respectively. The experimental elastic scattering angular distributions of the 6,7Li + 64Zn systems have been analyzed within the continuumdiscretized coupled-channels method, while the 6He + 64Zn data have been compared with both continuum-discretized coupled-channels and coupled-reaction-channels calculation

Comparison of the effects of couplings to breakup channels in reactions induced by 6Li and 6He on the same 64Zn target

The experimental elastic scattering angular distributions for the weakly bound nuclei 6,7Li and for the halo nucleus 6He on the same 64Zn target at several energies around the Coulomb barrier were measured at the Laboratori Nazionali del Sud (LNS, Italy) and at the Cyclotron Research Center, Louvain La Neuve (Belgium), respectively. The measured elastic scattering angular distributions of these three systems at the same center of mass energy have been compared. The experimental data of the 6,7Li+ 64Zn systems have been analyzed within the CDCC method, while the 6He+64Zn data have been compared with both both CDCC and CRC calculations

Effects of coupling to breakup in the 6,7 Li + 64 Zn systems at near-barrier energies

Elastic scattering angular distributions for the weakly bound nucleus Li7 on Zn64 have been measured in a wide angular range at energies around the Coulomb barrier. The present experimental data and our previously measured elastic scattering data for the system Li6+Zn64 have been analyzed within the continuum-discretized coupled-channels method, where the resonant and nonresonant states of the projectile are taken into account. In this theoretical framework, we have also analyzed our previously measured excitation functions of elastic scattering at backward angles and the corresponding barrier distributions for the same systems. A good agreement between the experimental data and the calculations has been observed. The obtained results, besides confirming the importance of the coupling to the breakup channels in collisions with weakly bound nuclei, show that, in the case of Li6, the inclusion of the resonant states of the projectile produces non-negligible effects.Ministerio de Economía y Competitividad (España) FIS2013-41994-PJunta de Andalucía FQM160 P07-FQM-02894Programa Consolider-Ingenio 2010 (España) CSD2007-0004

Coupling to continuum effects in the 6,7Li +64Zn reactions at energies around the Coulomb barrier

The elastic scattering angular distributions for the weakly bound nuclei 6Li and 7Li on 64Zn were measured in a wide angular range at energies around the Coulomb barrier. In addition, the excitation functions of quasi-elastic scattering at backward angles were measured and the corresponding barrier distributions were derived. The experimental data were analysed within the continuum-discretized-coupled-channel method. In this contribution, we will present a detailed study concerning the effects of the break-up channels in the 6,7Li +64 Zn reactions

Observation of 15 N + α resonant structures in 19 F using the thick target in inverse kinematics scattering method

The spectroscopy of 19 F is of interest for nuclear astrophysics and nuclear structure. In astrophysics, fluorine and the reactions producing and destroying it play a key role in constraining models of stars in different evolutionary stages, such as the asymptotic giant branch (AGB) stars, responsible of the production of about half of the elements heavier than Fe. In nuclear structure, 19 F has been subject to many investigations aiming at the identification of α and more exotic cluster structures. Also, its spectroscopy is very useful to constrain the nuclear properties of the 19 Ne mirror nucleus. In this work, we report on the measurement of the 15 N − α elastic scattering using the thick target inverse kinematics approach, allowing us to span a very large fluorine excitation energy range ( ∼ 6 –10 MeV). The use of 15 N − α scattering proves very useful to study α clustering in 19 F thanks to the likelihood for populating states with such a structure. Indeed, the R -matrix analysis of the measured differential cross sections shows the occurrence of many candidate α -cluster states of 19 F . It also calls for the redefinition of the spin-parity and widths of a number of 19 F states with respect to what reported in the literature

Probing proton halo effects in the 8B+64Zn collision around the Coulomb barrier

Proton halo effects in the 8B+64Zn reaction at an energy around 1.5 times the Coulomb barrier have been studied at HIE-ISOLDE CERN using, for the first time, the only existing postaccelerated 8B beam. This, together with the use of a high granularity and large solid angle detection system, allowed for a careful mapping of the elastic angular distribution, especially in the Coulomb-nuclear interference region. Contrary to what is observed for the one-neutron halo nucleus 11Be on the same target in a similar energy range, the analysis of the elastic scattering angular distribution shows only a modest suppression of the Coulomb-nuclear interference peak, with no remarkable enhancement of the total reaction cross-section. Inclusive angular and energy distributions of 7Be produced in direct reaction processes have also been measured. The comparison of these data with the results of theoretical calculations for the elastic and non-elastic breakup contributions indicate that both processes are important. Overall, the experimental data suggest a 8B collision dynamics at the barrier very different from the one of neutron halo nuclei, showing only modest effects of coupling to continuum. This behaviour can be interpreted as due to the presence of the additional Coulomb interactions halo-core and halo-target together with the presence of the centrifugal barrier felt by the valence proton of 8B.UE ENSAR2 Subvención nº 654002Istituto Nazionale di Fisica Nucleare (INFN) Italia, Science and Technology Facilities Council (STFC) Reino Unido y la Agencia Española de Financiación “ELEGANT” PGC2018-095640-B-100, FIS2017-88410-P, PDI2019- 104390GB-100, FPA2016-77689-C2-1-R, PGC2018-096994-B-C21, PGC2018-096994-B-C22 y RTI2018-098868-B-I0

Experimental investigation of exotic clustering in 13B and 14C using the resonance scattering method

In order to investigate the existence of molecular and/or exotic cluster configurations in Boron and Carbon n-rich isotopes we undertook two experiments: the first experimental study of exotic 9Li+α cluster states in 13B using the resonance scattering method at TRIUMF (Canada), and, with the same technique, the measurement of 10Be+α scattering at LNS in Catania, where a 10Be radioactive beam was produced for the first time. In order to measure the excitation function in a wide energy range, the beams were stopped in a Helium-flooded chamber. In the case of 13B, the elastic excitation function shows the presence of various peaks in an excitation energy region never explored before. In the case of 14C, our exclusive measurement of elastic scattering data with a high intensity beam, sheds some light on the contradictory previously published results [1, 2]

Breakup and n -transfer effects on the fusion reactions Li 6,7 + Sn 120,119 around the Coulomb barrier

This paper presents values of complete fusion cross sections deduced from activation measurements for the reactions Li6+Sn120 and Li7+Sn119, and for a projectile energy range from 17.5 to 28 MeV in the center-of-mass system. A new deconvolution analysis technique is used to link the basic activation data to the actual fusion excitation function. The complete fusion cross sections above the barrier are suppressed by about 70% and 85% with respect to the universal fusion function, used as a standard reference, in the Li6 and Li7 induced reactions, respectively. From a comparison of the excitation functions of the two systems at energies below the barrier, no significant differences can be observed, despite the two systems have different n-transfer Q values. This observation is supported by the results of coupled reaction channels (CRC) calculations