Suchergebnisse

Experimental studies of nuclear collisions involving light weakly bound nuclei show a systematic suppression of the complete fusion cross section by ∼30% with respect to the expectation for tightly bound nuclei, at energies above the Coulomb barrier. Although it is widely accepted that the phenomenon is related to the weak binding of these nuclei, the origin of this suppression is not fully understood. Here, we present a novel approach that provides the complete fusion for weakly bound nuclei and relates its suppression to the competition between the different mechanisms contributing to the reaction cross section. The method is applied to the 6,7Li+209Bi reactions, where we find that the suppression of complete fusion is mostly caused by the flux associated with nonelastic breakup modes, such as the partial capture of the projectile (incomplete fusion), whereas the elastic breakup mode is found to play a minor role. Finally, we demonstrate that the large α yields observed in these reactions can be naturally explained as a consequence of a Trojan Horse mechanism. ; National Science Foundation under Contract No. NSF-PHY-1520972 with Ohio University ; Ministerio de Ciencia,Innovación y Universidades (Projects No. FIS2014-53448-C2-1-P and No. FIS2017-88410-P) ; European Union's Horizon 2020 (Grant Agreement No. 654002)

The continuum structure of the unbound system 10 Li, inferred from the 9 Li(d,p) 10 Li transfer reaction, is reexamined. Experimental data for this reaction, measured at two different energies, are analyzed with the same reaction framework and structure models. It is shown that the seemingly different features observed in the measured excitation energy spectra can be understood as due to the different incident energy and angular range covered by the two experiments. The present results support the persistence of the N=7 parity inversion beyond the neutron dripline as well as the splitting of the well-known low-lying p-wave resonance. Furthermore, they provide indirect evidence that most of the ℓ=2 single-particle strength, including possible d 5/2 resonances, lies at relatively high excitations energies. ; Spanish Ministerio de Ciencia, Innovación y Universidades FIS2014-53448-C2-1-P FIS2017-88410-P ; FEDER funds FIS2014-53448-C2-1-P FIS2017-88410-P ; European Union 654002

Core-excitation effects in the scattering of two-body halo nuclei have been investigated in previous works. In particular, these effects have been found to affect in a significant way the breakup cross sections of neutron-halo nuclei with a deformed core. To account for these effects, appropriate extensions of the continuum-discretized coupled-channels (CDCC) method have been recently proposed. ; Ministerio de Economía y Competitividad y FEDER FIS2014-53448-C2-1-P ; European Union's Horizon 2020 654002

One-neutron removal (p,pn) reactions induced by two-neutron Borromean nuclei are studied within a Transfer-to-the-Continuum (TC) reaction framework, which incorporates the three-body character of the incident nucleus. The relative energy distribution of the residual unbound two-body subsystem, which is assumed to retain information on the structure of the original three-body projectile, is computed by evaluating the transition amplitude for different neutron-core final states in the continuum. These transition amplitudes depend on the overlaps between the original three-body ground-state wave function and the two-body continuum states populated in the reaction, thus ensuring a consistent description of the incident and final nuclei. By comparing different 11Li three-body models, it is found that the 11Li(p,pn)10Li relative energy spectrum is very sensitive to the position of the p1/2 and s1/2 states in 10Li and to the partial wave content of these configurations within the 11Li ground-state wave function. The possible presence of a low-lying d5/2 resonance is discussed. The coupling of the single particle configurations with the non-zero spin of the 9Li core, which produces a spin-spin splitting of the states, is also studied. Among the considered models, the best agreement with the available data is obtained with a 11Li model that incorporates the actual spin of the core and contains ∼31% of p1/2-wave content in the n-9Li subsystem, in accord with our previous findings for the 11Li(p,d)10Li transfer reaction, and a near-threshold virtual state. ; Ministerio de Economía y Competitividad FIS2014-53448-C2-1-P ; European Union Horizon 2020 research and innovation program 654002 ; Ministerio de Educación, Cultura y Deporte FPU13/04109

The Continuum-Discretized Coupled-Channels (CDCC) has been successfully employed to describe elastic and breakup of nuclear reactions induced by weakly bound projectiles. In this contribution, we review some other, less widespread applications of the CDCC wavefunction, some of them in combination with other reaction formalisms, which are being currently employed in the analysis of reactions involving three or more fragments in the initial or final state. ; National Science Foundation NSF-PHY-1520972 ; Ministerio de Ciencia, Innovación y Universidades FIS2017-88410-P ; European Union's Horizon 2020 654002

The Transfer to the Continuum method has been applied to describe the 11Li(p, pn) and 14Be(p, pn) reactions in inverse kinematics, using structure overlaps computed within a full three-body model for the projectile. Calculations agree with the available experimental data on the unbound 10Li and 13Be nuclei. ; Ministerio de Ciencia, Innovación y Universidades FIS2017-88410-P, FPA2016-77689-C2-1-R ; European Union's Horizon 2020 654002

Angular distributions of quasielastic scattering and breakup of the neutron-rich halo nucleus 11Be on a 208Pb 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 10Be core is taken into account. The angular and energy distributions of the 10Be 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 10Be 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. ; National Key Research and Development Program of China (Grant No. 2018YFA0404403) ; National Natural Science Foundation of China (Grant No. 11775013, No. 11947203, No. 11575256, and No. U1632138) ; Youth Innovation Promotion Association CAS (No. 2020411) ; Ministerio de Ciencia, Innovación y Universidades FIS2017-88410-P ; European Union's Horizon 2020 (Grant Agreement No. 654002)

New experimental results for the elastic scattering of He6 on Zn64 at incident energies of 15.0 and 18.0 MeV and He4 at 17.5 MeV along with results already published at 10.0 and 13.6 MeV, are presented. Elastic and α experimental cross sections are compared with coupled-reaction-channel, continuum-discretized coupled-channel, and DWBA inclusive-breakup models. The large yield of α particles observed at all measured energies can be explained by considering a nonelastic breakup mechanism. ; Spanish Ministerio de Economía y Competitividad and FEDER funds (FIS2014-53448-C2-1-P, FIS2017-88410P, FPA2016-77689-C2-1-R) ; European Union's Horizon 2020 654002

The one-neutron transfer reaction 9Li + 2H → 8Li + t has been investigated in an inverse kinematics experiment by bombarding a deuterated polypropylene target with a 2.36 MeV/u 9Li beam from the post-accelerator REX-ISOLDE at CERN. Excitation energies in 8Li as well as angular distributions of the tritons were obtained and spectroscopic factors deduced ; European Union Fifth Framework HPRI-CT-1999-00018 ; Comisión Interministerial de Ciencia y Tecnología FPA2002-04181-c04-02

The 9Li + 2H reaction has been investigated at 2.36 MeV/u at the REX-ISOLDE facility. In this Letter we focus on the 10Li + p channel which potentially holds spectroscopic information on the unbound nucleus 10Li. The experimental excitation energy spectrum and angular distribution are compared with CCBA calculations. These calculations clearly support the existence of a low-lying (s) virtual state, with a (negative) scattering length of the order as ∼ 13 - 24 fm and a p1 / 2 resonance with an energy of Er ≃ 0.38 MeV and a width of Γ ≃ 0.2 MeV. ; European Union Fifth Framework HPRI-CT-1999-00018 ; Comisión Interministerial de Investigaciones Científicas FPA2005-02379 y FPA2005-04460