Suchergebnisse

Background: The population and decay of two-nucleon resonances offer exciting new opportunities to explore dripline phenomena. A proper understanding of these systems requires a solid description of the three-body (core+N +N) continuum. The identification of a state with resonant character from the background of nonresonant continuum states in the same energy range poses a theoretical challenge. Purpose: Establish a robust theoretical framework to identify and characterize three-body resonances in a discrete basis, and apply the method to the two-neutron unbound system 16Be. Method: A resonance operator is proposed, which describes the sensitivity to changes in the potential. Resonances,understoodasnormalizablestatesdescribinglocalizedcontinuumstructures,areidentifiedfromthe eigenstates of the resonance operator with large negative eigenvalues. For this purpose, the resonance operator is diagonalizedinabasisofHamiltonianpseudostates,whichinthepresentworkarebuiltwithinthehyperspherical harmonics formalism using the analytical transformed harmonic oscillator basis. The energy and width of the resonance are determined from its time dependence. Results: The method is applied to 16Be in a 14Be+n+n model. An effective core+n potential, fitted to the available experimental information on the binary subsystem 15Be, is employed. The 0+ ground state resonance of 16Be presents a strong dineutron configuration. This favors the picture of a correlated two-neutron emission. Fitting the three body interaction to the experimental two-neutron separation energy |S2n|=1.35(10) MeV, the computed width is (0+)=0.16 MeV. From the same Hamiltonian, a 2+ resonance is also predicted with εr(2+)=2.42 MeV and (2+)=0.40 MeV. Conclusions: The dineutron configuration and the computed 0+ width are consistent with previous R-matrix calculationsforthetruethree-bodycontinuum.Theextractedvaluesoftheresonanceenergyandwidthconverge with the size of the pseudostate basis and are robust under changes in the basis parameters. This supports the reliability of the method in describing the properties of unbound core+N +N systems in a discrete basis. ; Spanish Ministerio de Ciencia, Innovación y Universidades, European Regional Development Fund (FEDER), (FIS2017-88410-P, FPA2016-77689-C2-1-R, FIS2014-51941-P ) ; European Union's Horizon 2020 (No. 654002)

Radiative capture reaction rates for 6He, 9Be and 17Ne formation at astrophysical conditions are studied within a three-body model using the analytical transformed harmonic oscillator method to calculate their states. An alternative procedure to estimate these rates from experimental data on low-energy breakup is also discussed. ; Ministerio de Economía y Competitividad FPA2016-77689-C2-1-R, FIS2014-53448-c2-1-P, FIS2014-51941-P ; Junta de Andalucía FQM-160, P11-FQM-7632 ; European Union 654002

In this work, we present our magnetron sputtering based methodology to produce amorphous silicon coatings with closed porosity, as a strategy to fabricate solid helium targets, in the form of supported or self-supported thin films, for nuclear reactions. We show how by changing the He working pressure it is possible to obtain highly porous homogeneous structures incorporating different He amounts. These porous coatings (a- Si:He) are very reproducible from run to run, and the high He amount incorporated makes them excellent candidates for solid He targets. The possibility of producing self-supported films is illustrated here, and its potential use in inverse kinematics experiments with radioactive beams is shown through the dispersion in forward geometry of a stable 6Li beam. Also the elastic scattering cross-sections for proton from helium were determined using an a-Si:He coating. The results agree well with the ones reported in the literature. These two examples validate our coatings as good candidates to be used as solid He targets in nuclear reactions. The stability of He inside the coatings, fundamental for its use as solid He targets, was investigated, both over time and after irradiation. The coatings proved to be very stable, and the amount of He inside the pores remains unaltered at least 2 years after deposition and after high irradiation fluence (5 × 1017 particles/cm2; with a dose rate of 5 × 1012 particles/(cm2 s)). ; Ministerio de Economía y Competitividad FPA2013-47327-C2-1-R, MAT2015-69035- REDC ; Consejo Superior de Investigaciones Científicas 201460E018 ; European Union CT-REGPOT-2011-285895

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 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 FPA2007-63074 ; European Union 212692

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