Search

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 $\ell=2$ single-particle strength, including possible $d_{5/2}$ resonances, lies at relatively high excitations energies., accepted for publication in Physics Letters B

In 1985, Hussein and McVoy [Nuc. Phys. A445 (1985) 124] elucidated a formula for the evaluation of the nonelastic breakup (“stripping”) contribution in inclusive breakup reactions. The formula, based on the spectator core model, acquires a particularly simple and appealing form in the eikonal limit, to the extent that it has become the standard procedure to analyze single-nucleon knockout reactions at intermediate energies. In this contribution, a critical assessment of this formula is presented and its connection with other, noneikonal expressions discussed. Some calculations comparing the different formulae are also presented for the one-nucleon removal of $$^{14}$$ O+ $$^{9}$$ Be reaction at several incident energies.

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., We wish to thank Dr. A. Bonaccorso for useful discussions and suggestions. This work has been supported by the European Commission Horizon 2020 framework trans-national access program of the EU project ENSAR2 (Grant no. 654002). Some of us acknowledge the support of the Istituto Nazionale di Fisica Nucleare (INFN), the UKRI STFC and the Spanish Funding Agency under the projects: “ELEGANT” PGC2018-095640-B-100, FIS2017-88410-P, PDI2019- 104390GB-100, FPA2016-77689-C2-1-R, PGC2018-096994-B-C21, PGC2018-096994-B-C22, RTI2018-098868-B-I00. L.A. is partially supported by DGAPA PAPIIT-IN107820 and CONACYT 314857. L.M.F is partially supported by the CERN associates program. D.G. is supported by the Portuguese FCT under the project CERN/FISPAR/0005/2017

In this review article we discuss the present status of direct nuclear reactions and the nuclear structure aspects one can study with them. We discuss the spectroscopic information we can assess in experiments involving transfer reactions, heavy-ion-induced knockout reactions and quasifree scattering with (p,2p), (p,pn), and (e,e'p) reactions. In particular, we focus on the proton-to-neutron asymmetry of the quenching of the spectroscopic strength., 138 pages, 63 figures

The first investigation of the single-particle structure of the bound states of 17C, via the d(16C, p) transfer reaction, has been undertaken. The measured angular distributions confirm the spin-parity assignments of 1/2+ and 5/2+ for the excited states located at 217 and 335 keV, respectively. The spectroscopic factors deduced for these states exhibit a marked single-particle character, in agreement with shell model and particle-core model calculations, and combined with their near degeneracy in energy provide clear evidence for the absence of the N = 14 sub-shell closure. The very small spectroscopic factor found for the 3/2+ ground state is consistent with theoretical predictions and indicates that the {\nu}1d3/2 strength is carried by unbound states. With a dominant l = 0 valence neutron configuration and a very low separation energy, the 1/2+ excited state is a one-neutron halo candidate., Comment: 7 pages, 5 figures, Accepted for publication in Physics Letters B

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)

We reexamine the elastic and breakup observables of the 11Be + 64Zn reaction at the near-barrier energy of 28.7 MeV. The measured quasi-elastic data are compared with CDCC and extended CDCC (XCDCC) calculations, the latter including the effect of the 10Be deformation. The angular distribution of emitted 10Be fragments, reported in the original analysis of this experiment, along with newly extracted 10Be energy distributions, are compared with calculations for the elastic breakup and non-elastic breakup contributions. Elastic breakup, computed with CDCC, accounts for most of the observed yields. The remaining difference (∼20%) is attributed to non-elastic breakup events (neutron absorption or target excitation) as confirmed by calculations performed with the model of Ichimura, Austern and Vincent (1985) [14]. Finally, the effect of post-acceleration in the energy distribution is investigated. This effect is well accounted for by the present CDCC calculations and, according to simple kinematical considerations, is estimated to be of the order of 1 MeV, and roughly independent of the scattering angle. Spanish Government FIS2014-53448-C2-1-P, FIS2017-88410-P European Union’s Horizon 2020, 654002

We present an investigation of the structure of 13Be obtained via a kinematically complete measurement of the (p,pn) reaction in inverse kinematics at 265 MeV/nucleon. The relative energy spectrum of 13Be is compared to Transfer-to-the-Continuum calculations which use as structure inputs the overlaps of the 14Be ground-state wave function, computed in a three-body model, with the unbound states of the 13Be residual nucleus. The key role of neutron p-wave orbital in the interpretation of the low-relative-energy part of the spectrum is discussed. Keywords: Quasi-free scattering, Borromean nuclei, Three-body model, Resonances

A novel method to extract the B(E1) strength of a weakly bound nucleus from experimental Coulomb dissociation data is proposed. The method makes use of continuum discretized coupled channels (CDCC) calculations, in which both nuclear and Coulomb forces are taken into account to all orders. This is a crucial advantage with respect to the standard procedure based on the Equivalent Photon Method (EPM) which does not properly take into account nuclear distortion, higher order coupling effects, or Coulombnuclear interference terms. The systematic and statistical uncertainties of this procedure are evaluated. The procedure is applied to the 11Be nucleus using two sets of available experimental data at different energies, for which seemingly incompatible B(E1) have been reported using the EPM. We show that the present procedure gives consistent B(E1) strengths, thus solving the aforementioned long-standing discrepancy between the two measurements., This work has been partially supported by the Spanish Ministerio de Ciencia, Innovación y Universidades and FEDER funds under projects FIS2017-88410-P and RTI2018-098117-B-C21 and by the European Union's Horizon 2020 research and innovation program under Grant Agreement No. 654002.

We present an account of the current status of the theoretical treatment of inclusive $(d,p)$ reactions in the breakup-fusion formalism, pointing to some applications and making the connection with current experimental capabilities. Three independent implementations of the reaction formalism have been recently developed, making use of different numerical strategies. The codes also originally relied on two different but equivalent representations, namely the prior (Udagawa-Tamura, UT) and the post (Ichimura-Austern-Vincent, IAV) representations. The different implementations have been benchmarked, and then applied to the Ca isotopic chain. The neutron-Ca propagator is described in the Dispersive Optical Model (DOM) framework, and the interplay between elastic breakup (EB) and non-elastic breakup (NEB) is studied for three Ca isotopes at two different bombarding energies. The accuracy of the description of different reaction observables is assessed by comparing with experimental data of $(d,p)$ on $^{40,48}$Ca. We discuss the predictions of the model for the extreme case of an isotope ($^{60}$Ca) currently unavailable experimentally, though possibly available in future facilities (nominally within production reach at FRIB). We explore the use of $(d,p)$ reactions as surrogates for $(n,\gamma)$ processes, by using the formalism to describe the compound nucleus formation in a $(d,p\gamma)$ reaction as a function of excitation energy, spin, and parity. The subsequent decay is then computed within a Hauser-Feshbach formalism. Comparisons between the $(d,p\gamma)$ and $(n,\gamma)$ induced gamma decay spectra are discussed to inform efforts to infer neutron captures from $(d,p\gamma)$ reactions. Finally, we identify areas of opportunity for future developments, and discuss a possible path toward a predictive reaction theory.

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 $^{11}$Li three-body models, it is found that the $^{11}$Li$(p,pn){^{10}}$Li relative energy spectrum is very sensitive to the position of the $p_{1/2}$ and $s_{1/2}$ states in $^{10}$Li and to the partial wave content of these configurations within the $^{11}$Li ground-state wave function. The possible presence of a low-lying $d_{5/2}$ resonance is discussed. The coupling of the single particle configurations with the non-zero spin of the $^{9}$Li 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 $^{11}$Li model that incorporates the actual spin of the core and contains $\sim$31\% of $p_{1/2}$-wave content in the $n$-$^9$Li subsystem, in accord with our previous findings for the $^{11}$Li(p,d)$^{10}$Li transfer reaction, and a near-threshold virtual state., 7 pages, 4 figures, submitted to PLB

We present angular distributions of the He 6 + Ni 58 scattering measured at three bombarding energies above the Coulomb barrier: E lab = 12.2 MeV , 16.5 MeV , and 21.7 MeV . The angular distributions have been analysed in terms of three- and four-body Continuum-Discretized Coupled-Channels calculations considering the effect of the 6 He breakup. A behaviour in the cross section at large angles has been observed which was reproduced only by the four-body Continuum-Discretized Coupled-Channels calculation.

Recent data on the differential angular distribution for the transfer reaction $^{11}$Li(p,d)$^{10}$Li at $E/A=5.7$ MeV in inverse kinematics are analysed within the DWBA reaction framework, using the overlap functions calculated within a three-body model of $^{11}$Li. The weight of the different $^{10}$Li configurations in the system's ground state is obtained from the structure calculations unambiguously. The effect of the $^{9}$Li spin in the calculated observables is also investigated. We find that, although all the considered models succeed in reproducing the shape of the data, the magnitude is very sensitive to the content of $p_{1/2}$ wave in the $^{11}$Li ground-state wave function. Among the considered models, the best agreement with the data is obtained when the $^{11}$Li ground state contains a $\sim$31\% of $p_{1/2}$ wave in the $n$-$^9$Li subsystem. Although this model takes into account explicitly the splitting of the $1^+$ and $2^+$ resonances due to the coupling of the $p_{1/2}$ wave to the $3/2^-$ spin of the core, a similar degree of agreement can be achieved with a model in which the $^{9}$Li spin is ignored, provided that it contains a similar p-wave content., 8 pages, 3 figures. Final version

The RIBRAS facility (Radioactive Ion Beams in Brasil) is installed in connection with the 8MV Pelletron tandem of the University of Sao Paulo Physics Institute. It consists of two superconducting solenoids which focalize light radioactive secondary beams of low energy, produced by transfer reactions. Recent experimental results include the elastic scattering and transfer reactions of 6He halo nucleus on 9Be, 27Al, 51V and 120Sn targets. The elastic scattering and transfer of 8Li and 7Be on several targets is also being studied. The transfer reaction 8Li(p,α)5He of astrophysical interest was also studied in the E c m = 0.2 – 2.5 MeV energy range.

The formal problem of three-body breakup in nuclear reactions is addressed. Two alternative treatments, namely, the direct breakup and transfer to the continuum approaches, are discussed and compared. Calculations for the reactions 8B+ 58Ni at 26 MeV and 6He + 208Pb at 22 MeV are presented and compared with existing data.

The elastic scattering of the radioactive halo nucleus 6He on 27Al target was measured at four energies close to the Coulomb barrier using the RIBRAS (Radioactive Ion Beams in Brazil) facility. The Sao 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 6He on 27Al are similar to those for stable, weakly bound projectiles as {6,7}Li, 9Be and larger than stable, tightly bound projectile as 16O on 27Al., 7 pages, 1 table, 3 figures

Elastic scattering angular distributions for the weakly bound nucleus $^{7}\mathrm{Li}$ on $^{64}\mathrm{Zn}$ 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 $^{6}\mathrm{Li}+^{64}\mathrm{Zn}$ 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 $^{6}\mathrm{Li}$, the inclusion of the resonant states of the projectile produces non-negligible effects.

The problem of the calculation of inclusive breakup cross sections in nuclear reactions is reexamined. For that purpose, the post-form theory proposed by Ichimura, Austern, and Vincent [Phys. Rev. C 32, 431 (1985)] is revisited, and an alternative derivation of the nonelastic breakup part of the inclusive breakup is presented, making use of the coupled-channels optical theorem. Using the distorted-wave Born approximation (DWBA) version of this model, several applications to deuteron and $^{6}\mathrm{Li}$ reactions are presented and compared with available data. The validity of the zero-range approximation of the DWBA formula is also investigated by comparing zero-range with full finite-range calculations.

We present a detailed analysis of the elastic scattering and breakup channel for the reaction of Li-11 on Pb-208 at incident laboratory energies of 24.3 and 29.8 MeV, measured at the radioactive ion beam facility of TRIUMF, in Vancouver, Canada. A large yield of Li-9 fragments was detected by four charged particle telescopes in a wide angular range. The experimental angular and energy distributions of these Li-9 fragments have been compared to coupled-reaction-channel and continuum-discretized coupled-channel calculations. The large production of Li-9 fragments at small angles can be explained by considering a direct breakup mechanism, while at medium-large angles a competition between direct breakup and neutron transfer to the continuum of the Pb-208 target was observed.

We address the problem of the post-prior equivalence in inclusive breakup reactions induced by weakly-bound nuclei. The problem is studied within the DWBA model of Ichimura, Austern, Vincent [Phys. Rev. C32, 431 (1985)]. The post and prior formulas obtained in this model are briefly recalled, and applied to several breakup reactions induced by deuterons and $^6$Li projectiles, to test their actual numerical equivalence. The different contributions of the prior-form formula are also discussed. A critical comparison with the prior-form distorted-wave Born approximation (DWBA) model of Udagawa and Tamura [Phys. Rev. C24, 1348 (1981)] is also provided., Comment: 6 pages, 2 figures, submitted to PRC

[Background]: Dynamic core-excitation effects have been found to be of importance in breakup reactions and may be of relevance when obtaining spectroscopic information from transfer reactions. [Purpose]: In this paper we extend the distorted-wave Born approximation (DWBA) formalism in order to allow for noncentral components in the core-core term appearing in the transition operator, which allows for dynamic core-excitation effects. Then we study these effects by applying the formalism to different (d,p) reactions. [Methods]: The expression of the nonlocal kernels required for the evaluation of the DWBA amplitudes has been extended so as to include noncentral parts in the core-core interaction. The DWBA scattering amplitude is then obtained by solving the corresponding inhomogeneous equation, with the new computed kernels, and the usual outgoing boundary conditions. A new DWBA code has been developed for this purpose. Results: For Be10(d,p)Be11, core-excitation effects are found to be almost negligible (, This work has been partially supported under grant FPA2009-07653, by the Spanish Consolider–Ingenio 2010 Programme CPAN (CSD2007-00042), by Junta de Andalucía (FQM160, P07-FQM-02894), and by Spanish Ministerio de Economía y Competitividad (FPA-2013-47327-C02-01-R) and under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. M.G.-R. acknowledges a research grant by the Spanish Ministerio de Educación, Cultura y Deporte.

A new method to calculate cross sections for $(p,pn)$ and $(p,2p)$ reactions measured under inverse kinematics conditions is proposed. The method uses the prior form of the scattering transition amplitude, and replaces the exact three-body wave function appearing in this expression by an expansion in terms of $p$-$n$ or $p$-$p$ states, covering the physically relevant excitation energies and partial waves. A procedure of discretization, similar to that used in continuum-discretized coupled-channels calculations, is applied in order to make this expansion finite and numerically tractable. The proposed formalism is non-relativistic but several relativistic kinematical corrections are applied to extend its applicability to energies of current interest. The underlying optical potentials for the entrance and exit channels are generated microscopically, by folding an effective density-dependent G-matrix with the density of the composite nucleus. Numerical calculations for $^{12}$C($p$,$2p$), $^{12}$C($p$,$pn$) and $^{23}$O($p$,$pn$) at $\sim$400~MeV/nucleon are presented to illustrate the method. The role of final-state interactions and Pauli principle between the outgoing nucleons is also discussed., 14 pages, 11 figures, to be published in Phys. Rev. C

The elastic scattering differential cross section is calculated for proton scattering from 6He at 717 MeV, using single-scattering terms of the multiple-scattering expansion of the total transition amplitude. We analyze the effects of different scattering frameworks, specifically the factorized impulse approximation and the fixed scatterer (adiabatic) approximation.

The one-neutron transfer reaction Li-9 + H-2 -> Li-8 + t has been investigated in an inverse kinematics experiment by bombarding a deuterated polypropylene target with a 2.36 MeV/u Li-9 beam from the post-accelerator REX-ISOLDE at CERN. Excitation energies in Li-8 as well as angular distributions of the tritons were obtained and spectroscopic factors deduced. (c) 2006 Elsevier B.V. All rights reserved.

11 pages, 10 figures.-- PACS nrs.: 25.60.Dz, 25.60.Gc, 25.60.Bx, 21.10.Gv, 27.20.+n.-- 2nd version of the pre-print: Submitted on 18 Jul 2005 (v1), last revised 17 Nov 2005 (this version, v2), minor corrections made.-- Published in: Nuclear Physics A, Vol.765, Issues 3-4, pages 294-306 (6 February 2006).-- et al., Quasi-elastic scattering of 6He at E_lab=27 MeV from 197Au has been measured in the angular range of 6-72 degrees in the laboratory system employing LEDA and LAMP detection systems. These data, along with previously analysed data of 6He + 208Pb at the same energy, are analyzed using Optical Model calculations. The role of Coulomb dipole polarizability has been investigated. Large imaginary diffuseness parameters are required to fit the data. This result is an evidence for long range absorption mechanisms in 6He induced reactions., The authors thank the staff at the Cyclotron Research Centre accelerator facility in Louvain-la-Neuve, Belgium, for providing us with an intense and good quality radioactive beam. ORK acknowledges a grant from the Iranian government and support from the University of Sevilla for his stay at this university. PJW, TD, ACS, AL, ADP and WBS would like to acknowledge support from the British EPSRC. AMSB, IMB, MVA, AM, MAGA and JGC would like to acknowledge support from the Spanish MCyT under projects FPA2003-05958 and FPA2005-04460. AMSB acknowledges a research grant from the Spanish MCyT.

A distorted wave born approximation is applied to give a simultaneous description of elastic scattering, total reaction, fusion and one neutron transfer cross sections for the system 9Be + 208Pb at energies below and above the Coulomb barrier energy. In the approach, Woods–Saxon optical potentials are applied. For the entrance channel, the imaginary part W of the optical potential U is split into two parts; a volume part W F which is responsible for fusion absorption and a surface part W DR which accounts for direct reactions. The optical potential parameters are determined from a simultaneous χ 2 -analysis of recent experimental data of (a) elastic scattering and complete fusion and (b) elastic scattering and total fusion (complete + incomplete). In this manner, an account of a single α-particle partial fusion can be given. The one-neutron transfer cross section is determined with the same elastic distorted waves obtained from U. A search of the threshold anomaly is made for the real and imaginary parts of U although a no conclusive determination of it can be given. In general the results obtained in the calculations are in close agreement with the data.

The formalism to describe the scattering of a weakly bound projectile nucleus by a heavy target is investigated, using the Uncorrelated Scattering Approximation. The main assumption involved is to neglect the correlation between the fragments of the projectile in the region where the interaction with the target is important. It is shown that the angular momentum of each fragment with respect to the target is conserved. Moreover, when suitable approximations are assumed, the kinetic energy of each fragment is also shown to be conserved. The S-matrix for the scattering of the composite system can be written as a combination of terms, each one being proportional to the product of the S-matrices of the fragments., Comment: 27 pages, 6 figures, submitted to Nucl. Phys. A (v2: minor misprints and grammatical errors corrected)

One-neutron halo nuclei, composed by a weakly-bound particle coupled to a core nucleus, are studied within a particle-plus-core model. A semi-microscopic method to generate the two-body Hamiltonian of such a system, including core excitation, is proposed. The method consists in generating the spin-independent part of the valence-core interaction using a single-folding procedure, convoluting a realistic nucleon-nucleon (NN) interaction with the core transition densities. The latter are calculated with the Antisymetrized Molecular Dynamics (AMD) method. The prescription is applied to the well known halo nucleus, $^{11}$Be, as a test case. The results show an important predictive power that opens a door to the understanding of other lesser known halo nuclei. In order to show the potential usefulness of the method, it is applied to analyze the structure of $^{19}$C., Comment: 11 pages, 7 figures, 3 tables (version to appear in Phys. Rev. C)

The effect of dipole polarizability in the scattering of deuterons by 208 Pb at energies around the Coulomb barrier is studied, using dynamic polarization potentials. At energies well below the barrier, we find that the dynamic polarization potential, which is complex and energy-dependent in general, can be approximated by the adiabatic expression, while the nuclear potential is negligible. At energies around and above the Coulomb barrier, the inclusion of the dynamic polarization potential along with the nuclear potential allows for a better fit of the elastic cross sections. The nuclear potentials obtained from the fit have reasonable values of the diffuseness parameters and their energy dependence is consistent with dispersion relations.

Angular distributions of the differential cross section and the second-rank tensor analysing power T 20 have been measured for the one-proton transfer reaction induced by polarized 7 Li on 208 Pb at 33 MeV leading to several states in 209 Bi. The experimental data were analysed simultaneously with data for elastic and inelastic scattering of 7 Li by means of CCBA and CRC calculations. The spectroscopic factors for 209 Bi states are obtained.

Motivation: Detailed experimental knowledge of the level structure of light weakly bound nuclei is necessary to guide the development of new theoretical approaches that combine nuclear structure with reaction dynamics. Purpose: The resonant structure of 8 B is studied in this work. Method: Excitation functions for elastic and inelastic 7 Be+p scattering were measured using a 7 Be rare isotope beam. Excitation energies ranging between 1.6 and 3.4 MeV were investigated. An R-matrix analysis of the excitation functions was performed. Results: New low-lying resonances at 1.9, 2.5, and 3.3 MeV in 8 B are reported with spin-parity assignment 0 + , 2 + , and 1 + , respectively. Comparison to the Time Dependent Continuum Shell (TDCSM) model and ab initio no-core shell model/resonating-group method (NCSM/RGM) calculations is performed. This work is a more detailed analysis of the data first published as a Rapid Communication. [J.P. Mitchell, et al, Phys. Rev. C 82, 011601(R) (2010)] Conclusions: Identification of the 0 + , 2 + , 1 + states that were predicted by some models at relatively low energy but never observed experimentally is an important step toward understanding the structure of 8 B. Their identification was aided by having both elastic and inelastic scattering data. Direct comparison of the cross sections and phase shifts predicted by the TDCSM and ab initio No Core Shell Model coupled with the resonating group method is of particular interest and provides a good test for these theoretical approaches.

The effect of core excitation in the elastic scattering and breakup of a two-body halo nucleus on a stable target nucleus is studied. The structure of the weakly-bound projectile is described in the weak-coupling limit, assuming a particle-rotor model. The eigenfunctions and the associated eigenvalues are obtained by diagonalizing this Hamiltonian in a square-integrable basis (pseudo-states). For the radial coordinate between the particle and the core, a transformed harmonic oscillator (THO) basis is used. For the reaction dynamics, an extension of the Continuum-Discretized Coupled-Channels (CDCC) method, which takes into account dynamic core excitation and deexcitation due to the presence of non-central parts in the core-target interaction, is adapted to be used along with a pseudo-states (PS) basis., Comment: 11 pages, 8 figures

In this paper details of the experimental procedure and data analysis of the collision of 11Be+64Zn around the Coulomb barrier are described and discussed in the framework of different theoretical approaches. In a previous work [ A. Di Pietro et al. Phys. Rev. Lett. 105 022701 (2010)], the elastic scattering angular distribution of the collisions 9, 10Be+64Zn as well as the angular distribution for the quasielastic scattering and transfer/breakup cross sections for the 11Be+64Zn reaction were briefly reported. The suppression of the quasielastic angular distribution in the Coulomb-nuclear interference angular region observed in the collision of the 11Be halo nucleus with respect to the other two beryllium isotopes was interpreted as being caused by a long-range absorption owing to the long decay length of the 11Be wave function. In this paper, new continuum-discretized coupled-channel calculations of the 11Be+64Zn reaction are reported in the attempt to interpret the effect of coupling with the breakup channels on the measured cross sections. The calculations show that the observed suppression of the Coulomb-nuclear interference peak is caused by a combined effect of Coulomb and nuclear couplings to the breakup channels.

The quantum description of a particle moving in a deformed potential is investigated. A pseudostate (PS) basis is used to represent the states of the composite system. This PS basis is obtained by diagonalizing the system Hamiltonian in a family of square integrable functions. In this work the transformed harmonic oscillator (THO) functions, obtained from the solutions of the harmonic oscillator using a local scale transformation (LST), are used. The proposed method is applied to the 11Be nucleus, treated in a two-body model (10Be+n). Structure observables have been studied. Wave functions and energies obtained for the bound states and some low-lying resonances are compared with those obtained by direct integration of the Schrödinger equation. The dipole and quadrupole electric transition probabilities for the low-energy continuum have been calculated in the THO basis, and compared with the exact distributions obtained with the scattering states. © 2012 American Physical Society., This work has been partially supported by the Spanish Ministerio de Ciencia e Innovación and FEDER funds under Projects No. FIS2011-28738-c02-01, No. FPA2009-07653, and No. FPA2009-08848, by the Spanish Consolider-Ingenio 2010 Programme CPAN (CSD2007-00042), and by Junta de Andalucía (FQM160, P07-FQM-02894). J.A.L. acknowledges a research grant by the Ministerio de Ciencia e Innovación.

We investigate the phenomenon of core excitation in the inelastic and breakup of two-body halo nuclei, composed by a valence nucleon and a core. To evaluate the importance of this effect we propose a simple reaction model based on an extension of the standard distorted wave Born approximation (DWBA) method. The model takes into account core-excited admixtures in the states of the composite projectile, as well as the possibility of dynamic core excitation due to the interaction of the core with the target. As an application of the model, we present calculations for the breakup of 11Be on a proton target at an incident energy of 63.7 MeV/nucleon, comparing it with the available data for this reaction. We find that the data are well reproduced by the model and that the effect of dynamic core excitation is essential to explain the observed cross section. Ministerio de Ciencia e Innovación (España) FPA2009-07653 Programa Consolider-Ingenio 2010 CSD2007-00042

The reaction 8Li + 2H has been studied in inverse kinematics at the incident energy of 3.15 MeV/nucleon, using the REX-ISOLDE post-accelerator. The reaction channels corresponding to (d,p), (d,d), and (d,t) reactions populating ground states and low-lying excited states in 7–9Li have been identified and the related angular distributions extracted and compared with coupled-channels, distorted-wave Born approximation (DWBA), and coupled-reaction-channels calculations. For the inelastic and (d,t) channels we find that higher order effects are very important and hence one needs to go beyond the simple DWBA to extract reliable structure information from these processes.

This work has been supported by the Spanish MICINN under projects FPA2005-04460, FPA200502379, FPA2006-13807-c02-01, FPA2007-63074, FPA2009-07653, FPA2009-07387 and FPA2010 22131-C02-01, by the Junta de Andalucia project FQM-4964, by the Spanish Consolider-Ingenio 2010 Programme CPAN (CSD2007-00042) and Programme Multi-Dark (CSD2009-00064), by the European Community-Access to Research Infrastructure action of the Improving Human Potential Program Contract, No. HPRI-CT-1999-00110, and by the Belgian Program P5/07 on interuniversity attraction poles of the Belgian-state Federal Services for Scientific, Technical and Cultural Affairs. L. Acosta acknowledges financial support by the Universidad de Huelva.

This is the publisher's version, also available electronically from http://journals.aps.org/prc/abstract/10.1103/PhysRevC.84.011301.

New data for the $^{6}\mathrm{He}+^{9}\mathrm{Be}$ reaction at ${E}_{\mathrm{lab}}=16.2$ and 21.3 MeV have been taken and analyzed. The effect of the collective couplings to the excited states of the target has been studied by means of coupled-channels calculations, using a double-folding potential for the bare interaction between the colliding nuclei, supplemented with a phenomenological imaginary part of Woods-Saxon type. In addition, three- and four-body continuum-discretized coupled-channels calculations have been performed to investigate the effect of the projectile breakup on the elastic scattering. Both effects, the coupling to target and projectile excited states, are found to affect significantly the elastic scattering. The trivial local polarization potential extracted from the continuum-discretized coupled-channels calculations indicates that continuum couplings produce a repulsive real part and a long-range imaginary part in the projectile-target interaction.

The resonant breakup of $^{19}\mathrm{C}$ on a proton target at 70 MeV/nucleon is analyzed using Faddeev--Alt, Grassberger, Sandhas (Faddeev-AGS) and continuum-discretized coupled-channels (CDCC) reaction frameworks, where in both cases a three-body model (${}^{18}$$\text{C}+n+p$) for the reaction is considered. Taking a $^{18}\mathrm{C}$ $+$ $p$ potential from a global nucleon-nucleus parametrization and a $L$-independent Gaussian proton-neutron potential, both methods provide very similar results for the calculated observables. However, when this simplified proton-neutron potential is replaced by the more realistic CD-Bonn potential, the breakup cross section, calculated with the Faddeev AGS formalism, decreases by almost one order of magnitude, largely underestimating the experimental data. From this calculation, we conclude that, within a core $+$ valence neutron model, the single-particle mechanism gives a negligible contribution to the calculated resonant breakup and therefore core-excitation mechanisms should be taken into account.

The scattering of a weakly bound three-body system by a target is studied within the four-body continuum-discretized coupled-channels (4b-CDCC) framework. Two different methods, the transformed harmonic oscillator (THO) method and the binning procedure, are used for discretizing the three-body continuum. The formalism is applied to different reactions induced by the Borromean nucleus 6He at energies around the Coulomb barrier: 6He+64Zn at 13.6 MeV, 6He+120Sn at 17.4 MeV, and 6He+208Pb at 22 MeV. Elastic cross section distributions are presented for these reactions comparing both discretization methods, THO and binning, as the mass of the target increases., This work has been supported by the Spanish projects FPA2009-07653 and CSD2007-00042 and the Andalusian project P07-FQM-02894.

The collision $^{6}\mathrm{He}+^{120}\mathrm{Sn}$ has been investigated at four energies near the Coulomb barrier. A large yield of $\ensuremath{\alpha}$ particles has been detected, with energies around the energy of the scattered $^{6}\mathrm{He}$ beam. The energy and angular distributions of the $\ensuremath{\alpha}$ particles have been analyzed and compared with breakup and neutron transfer calculations.

Excitation functions of elastic and inelastic $^{7}\mathrm{Be}+p$ scattering were measured in the energy range between 1.6 and 2.8 MeV in the c.m. An $R$-matrix analysis of the excitation functions provides strong evidence for new positive parity states in $^{8}\mathrm{B}$. A new ${2}^{+}$ state at an excitation energy of 2.55 MeV was observed, and a new ${0}^{+}$ state at 1.9 MeV is tentatively suggested. The $R$-matrix and time-dependent continuum shell model were used in the analysis of the excitation functions. The new results are compared to the calculations of contemporary theoretical models.

The elastic scattering of $^{6}\mathrm{He}$ on $^{120}\mathrm{Sn}$ has been measured at four energies above the Coulomb barrier using the $^{6}\mathrm{He}$ beam produced at the RIBRAS (Radioactive Ion Beams in Brasil) facility. The elastic angular distributions have been analyzed with the optical model and three- and four-body continuum-discretized coupled-channels calculations. The total reaction cross sections have been derived and compared with other systems of similar masses.

A comparison between full few-body Faddeev/Alt-Grassberger-Sandhas (Faddeev/AGS) and continuum-discretized coupled channels (CDCC) calculations is made for the resonant and nonresonant breakup of $^{11}$Be on proton target at 63.7 MeV/u incident energy. A simplified two-body model is used for $^{11}$Be which involves an inert $^{10}$Be(0$^+$) core and a valence neutron. The sensitivity of the calculated observables to the nucleon-nucleon potential dynamical input is analysed. We show that with the present NN and N-core dynamics the results remain a puzzle for the few-body problem of scattering from light exotic halo nuclei.

El pdf del artículo es la versión pre-print: arXiv:1004.1911v1, We present an optical model (OM) analysis of the elastic scattering data of the reactions 6He+27Al and 6He+208Pb at incident energies around the Coulomb barrier. The bare part of the optical potential is constructed microscopically by means of a double folding procedure, using the São Paulo prescription without any renormalization. This bare interaction is supplemented with a Coulomb dipole polarization (CDP) potential, which takes into account the effect of the dipole Coulomb interaction. For this CDP potential, we use an analytical formula derived from the semiclassical theory of Coulomb excitation. The rest of the optical potential is parametrized in terms of Woods-Saxon shapes. In the 6He+208Pb case, the analysis confirms the presence of long range components, in agreement with previous works. Four-body Continuum-Discretized Coupled-Channels calculations have been performed in order to better understand the features of the optical potentials found in the OM analysis. This study searches to elucidate some aspects of the optical potential of weakly bound systems, such as the dispersion relation and the long range (attractive and absorptive) mechanisms. © 2010 Elsevier B.V., This work has been supported by the Spanish Ministerio de Ciencia e Innovación under project FPA2006-13807-C02-01, the local government of Junta de Andalucía under the excellence project P07-FQM-02894 and the Spanish Consolider-Ingenio 2010 Programme CPAN (CSD2007-00042).

The ability of a recently developed square-integrable discrete basis to represent the properties of the continuum of a two-body system is investigated. The basis is obtained performing a simple analytic local scale transformation to the harmonic oscillator basis. Scattering phase-shifts and the electric transition probabilities B(E1) and B(E2) have been evaluated for several potentials using the proposed basis. Both quantities are found to be in excellent agreement with the exact values calculated from the true scattering states. The basis has been applied to describe the projectile continuum in the He6 scattering by C12 and Pb208 targets at 240 MeV/nucleon and the Be11 scattering by C12 at 67 MeV/nucleon. The calculated breakup differential cross sections are found to be in very good agreement with the available experimental data for these reactions. © 2010 The American Physical Society., This work has been partially supported by the Spanish Ministerio de Ciencia e Innovación under Projects FIS2008-04189, FPA2009-07653, and FPA2009-08848 and by the Spanish Consolider-Ingenio 2010 Programme CPAN (CSD2007-00042). J.A.L. acknowledges a research grant from the Ministerio de Ciencia e Innovación.