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R A Broglia - One of the best experts on this subject based on the ideXlab platform.

  • The 9Li(d,p) reaction, a specific probe of 10Li, paradigm of Parity--inverted nuclei around N=6 closed shell
    arXiv: Nuclear Theory, 2018
    Co-Authors: Francisco Barranco, Gregory Potel, E. Vigezzi, R A Broglia
    Abstract:

    We show, within the framework of renormalized nuclear field theory and of the induced reaction surrogate formalism, that the highly debated $^{10}$Li structure, observed in a recent $^9$Li(d,p)$^{10}$Li one--neutron transfer experiment is consistent with or better, requires the presence of a virtual $1/2^+$ state of similar single--particle strength than that of the $1/2^-$ resonance at 0.45$\pm$ 0.03 MeV. Based on continuum spectroscopy self-energy techniques, we find that the physical mechanism responsible for Parity Inversion in $^{10}_3$Li is the same as that at the basis of the similar phenomenon observed in $^{11}_4$Be and to that needed in $^{11}$Li to have an important $s$--wave ground state component. Furthermore, it is also consistent with the (normal) sequence of the $1p_{1/2}$ and $2s_{1/2}$ levels in the $N=7$ isotones $^{12}_5$B and $^{13}_6$C.

  • one and two neutron halo at the dripline from 11be to 11li and back 10li and Parity Inversion
    arXiv: Nuclear Theory, 2018
    Co-Authors: R A Broglia, Gregory Potel, F Barranco, E. Vigezzi
    Abstract:

    The nuclei 11Be and 11Li provide paradigmatic examples of one-and two- neutron halo systems. Because the reaction 1H(11Li,9Li)3H is dominated by successive transfer, one can use the quantitative picture emerging from a nu- clear field theory description of the structure and reaction mechanism of the above Cooper pair transfer process and of the 2H(10Be,11Be)1H and 1H(11Be,10Be)2H reactions, to shed light on the structure of 10Li. This analysis provides important support for a Parity inverted scenario with a 1/2+ virtual state at about 0.2 MeV.

  • Parity Inversion breakdown of shell closure and particle vibration coupling in be isotopes
    arXiv: Nuclear Theory, 2008
    Co-Authors: G Gori, E. Vigezzi, F Barranco, R A Broglia
    Abstract:

    The properties of finite many-body systems arestrongly influenced by spatial quantization [1] leading tomarked shell structures [2]. This type of quantal sizeeffects are, on the other hand, renormalized in an impor-tant way by zero point fluctuations [3, 4]. The smallerthe system is, the largest the surface/volume ratio is andthe strongest these effects may become. In particular,the interweaving of single-particle motion and of collec-tive vibrations of the surface of atomic nuclei can leadto state dependent effective masses which, for light sys-tems can even invert the sequence of particular levels,thus altering the magic numbers associated with closedshell. While the standard parametrization of the single-particle potential [2] indicates the states 0p

  • Parity Inversion and breakdown of shell closure in be isotopes
    Physical Review C, 2004
    Co-Authors: G Gori, E. Vigezzi, F Barranco, R A Broglia
    Abstract:

    The coupling of single-particle motion and of vibrations in $_{4}^{11}\mathrm{Be}$ produces dressed neutrons which spend only a fraction of the time in pure single-particle states, and which weighing differently from the bare neutrons lead to Parity Inversion. The interaction of the two least bound neutrons in the ground state of $_{4}^{12}\mathrm{Be}$ mediated by the ${v}_{14}$ Argonne nucleon-nucleon potential and by the exchange of surface vibrations of the core $^{10}\mathrm{Be}$ gives rise to a strongly correlated state, where the two valence neutrons are distributed over ${s}^{2},{p}^{2}$, and ${d}^{2}$ configurations, resulting in the breaking of the $N=8$ shell closure.

Yoshiko Kanada-en'yo - One of the best experts on this subject based on the ideXlab platform.

  • Nuclear clusters and nuclear molecules
    Physics Reports, 2006
    Co-Authors: W. Von Oertzen, Martin Freer, Yoshiko Kanada-en'yo
    Abstract:

    Abstract Clustering has long been known to be influential in the structure of ground and excited states of N = Z nuclei. States close to the decay thresholds are of particular interest, as clustering becomes dominant. Recent studies of loosely bound light neutron-rich nuclei have focused attention on structures based on clusters and additional valence neutrons, which give rise to covalent molecular binding effects. These nuclear molecules appear only at the extremes of deformation, in the deformed shell model they are referred to as super- and hyper-deformed. The beryllium isotopes provide the first examples of such states in nuclear physics. Further nuclear molecules consisting of unequal cores and also with three centres can be considered. These arise in the isotopes of neon and carbon, respectively. Molecular states in intrinsically asymmetric configurations give rise to Parity (Inversion) doublets. Examples of recent experiments demonstrating the molecular structure of the rotational bands in beryllium isotopes are presented. Further experimental evidence for bands as Parity doublets in nuclei with valence neutrons in molecular orbits is also analysed. Work on chain states (nuclear polymers) in the carbon isotopes is discussed. These are the first examples of hyper-deformed structures in nuclei with an axis ratio of 3:1. Future perspectives are outlined based on a threshold diagram for covalent nuclear molecules with clusters bound via neutrons in covalent molecular configurations.

  • Nuclear clusters and nuclear molecules
    Physics Reports, 2006
    Co-Authors: W. Von Oertzen, Martin Freer, Yoshiko Kanada-en'yo
    Abstract:

    Clustering has long been known to be influential in the structure of ground and excited states of N = Z nuclei. States close to the decay thresholds are of particular interest, as clustering becomes dominant. Recent studies of loosely bound light neutron-rich nuclei have focused attention on structures based on clusters and additional valence neutrons, which give rise to covalent molecular binding effects. These nuclear molecules appear only at the extremes of deformation, in the deformed shell model they are referred to as super- and hyper-deformed. The beryllium isotopes provide the first examples of such states in nuclear physics. Further nuclear molecules consisting of unequal cores and also with three centres can be considered. These arise in the isotopes of neon and carbon, respectively. Molecular states in intrinsically asymmetric configurations give rise to Parity (Inversion) doublets. Examples of recent experiments demonstrating the molecular structure of the rotational bands in beryllium isotopes are presented. Further experimental evidence for bands as Parity doublets in nuclei with valence neutrons in molecular orbits is also analysed. Work on chain states (nuclear polymers) in the carbon isotopes is discussed. These are the first examples of hyper-deformed structures in nuclei with an axis ratio of 3:1. Future perspectives are outlined based on a threshold diagram for covalent nuclear molecules with clusters bound via neutrons in covalent molecular configurations. © 2006 Elsevier B.V. All rights reserved.

W. Von Oertzen - One of the best experts on this subject based on the ideXlab platform.

  • Nuclear Clusters and Covalent Molecules on the femto‐scale
    2010
    Co-Authors: W. Von Oertzen
    Abstract:

    Nuclear clusters like alpha-particles light N = Z nuclei are the building blocks of nuclear molecules. With additional 'valence' neutrons, which find there place in quantum mechanical two-center orbits a variety of covalently bound states in nuclei have been established in the last decade: in isotopes of {sup 9-12}Be, {sup 13-14}C and {sup 21}Ne. More recently we have studied molecular states in {sup 18,19,20}O-isotopes using the ({sup 7}Li,p) reaction on {sup 12,13,14}C targets at E{sub lab}({sup 7}Li) = 44 MeV. The systematics of the energies and cross sections show rotational bands with high moments of inertia. These are characteristic of large deformations or molecular structures where the clusters are well separated. Generally the large scale shell model calculations are unable to reproduce these cluster bands. With two clusters of different size (e.g. ({sup 14}C x {sup 4}He), or ({sup 16}O x {sup 4}He)) intrinsically reflection asymmetric shapes arise. The molecular structures appear as rotational bands split into Parity Inversion doublets.

  • The 14C‐Cluster and Molecular bands in the Oxygen Isotopes 18,20O
    AIP Conference Proceedings, 2009
    Co-Authors: W. Von Oertzen, T. Dorsch, H. G. Bohlen
    Abstract:

    We have studied states in 18O and 20O with the (7Li,p) reaction on 12C and 14C targets at Elab(7Li) = 44 MeV, using the high resolution Q3D magnetic spectrometer at the Maier‐Leibnitz‐Laboratory in Munich. The systematics of the excitation energies and cross sections were used to construct rotational bands with high moments of inertia. The bands observed are discussed in terms of underlying (14C⊗4He)‐cluster structure for 18O, and for 20O the cluster structures are (14C⊗6He) and (14C⊗2n⊗α). The intrinsically reflection asymmetric shapes give rise to molecular bands, which appear as Parity Inversion doublets.

  • Nuclear clusters and nuclear molecules
    Physics Reports, 2006
    Co-Authors: W. Von Oertzen, Martin Freer, Yoshiko Kanada-en'yo
    Abstract:

    Abstract Clustering has long been known to be influential in the structure of ground and excited states of N = Z nuclei. States close to the decay thresholds are of particular interest, as clustering becomes dominant. Recent studies of loosely bound light neutron-rich nuclei have focused attention on structures based on clusters and additional valence neutrons, which give rise to covalent molecular binding effects. These nuclear molecules appear only at the extremes of deformation, in the deformed shell model they are referred to as super- and hyper-deformed. The beryllium isotopes provide the first examples of such states in nuclear physics. Further nuclear molecules consisting of unequal cores and also with three centres can be considered. These arise in the isotopes of neon and carbon, respectively. Molecular states in intrinsically asymmetric configurations give rise to Parity (Inversion) doublets. Examples of recent experiments demonstrating the molecular structure of the rotational bands in beryllium isotopes are presented. Further experimental evidence for bands as Parity doublets in nuclei with valence neutrons in molecular orbits is also analysed. Work on chain states (nuclear polymers) in the carbon isotopes is discussed. These are the first examples of hyper-deformed structures in nuclei with an axis ratio of 3:1. Future perspectives are outlined based on a threshold diagram for covalent nuclear molecules with clusters bound via neutrons in covalent molecular configurations.

  • Search for cluster structure of excited states in ^14 C
    The European Physical Journal A - Hadrons and Nuclei, 2004
    Co-Authors: W. Von Oertzen, H. G. Bohlen, M. Milin, Tz Kokalova, S. Thummerer, A. Tumino, R. Kalpakchieva, T. N. Massey, Y. Eisermann, G. Graw
    Abstract:

    We have studied three different 2n-transfer reactions on a ^12C target, the 2p pick-up reaction on ^16O and the ^5He transfer in the reaction ^9Be(^7Li,d)^14C. Combined with a systematic search through experimental results for transfer reactions, inelastic excitations and other data, we have established an almost complete spectroscopy for ^14C up to 18 MeV excitation. We identify states with single-particle structure that have oblate shapes and states corresponding to proton excitations that are connected to oblate (triangular) cluster states. Further we list states of prolate shape which have no simple structure related to the low-lying oblate states of ^12C. These are proposed to have strong $\alpha$ -clustering and to form rotational bands as a Parity Inversion doublet, with high moment of inertia. With these results it is possible for the first time to identify chain states expected in the isotope ^14C.

  • Search for cluster structure of excited states in 14 C
    European Physical Journal A, 2004
    Co-Authors: W. Von Oertzen, H. G. Bohlen, M. Milin, Tz Kokalova, S. Thummerer, A. Tumino, R. Kalpakchieva, T. N. Massey, Y. Eisermann, G. Graw
    Abstract:

    We have studied three different 2n-transfer reactions on a 12C target, the 2p pick-up reaction on 16O and the 5He transfer in the reaction 9Be(7Li,d)14C. Combined with a systematic search through experimental results for transfer reactions, inelastic excitations and other data, we have established an almost complete spectroscopy for 14C up to 18 MeV excitation. We identify states with single-particle structure that have oblate shapes and states corresponding to proton excitations that are connected to oblate (triangular) cluster states. Further we list states of prolate shape which have no simple structure related to the low-lying oblate states of 12C. These are proposed to have strong \(\alpha\)-clustering and to form rotational bands as a Parity Inversion doublet, with high moment of inertia. With these results it is possible for the first time to identify chain states expected in the isotope 14C.

Guillaume Hupin - One of the best experts on this subject based on the ideXlab platform.

  • Application of an ab-initio S-matrix to data analysis of transfer to the continuum reactions populating 11Be.
    arXiv: Nuclear Theory, 2019
    Co-Authors: A. Bonaccorso, Guillaume Hupin, P. Navrátil, F. Cappuzzello, D. Carbone, M. Cavallaro, S. Quaglioni
    Abstract:

    Recently, the bound and continuum spectrum of 11Be has been calculated within the ab-initio no-core shell model with continuum (NCSMC) method successfully reproducing the Parity Inversion in the ground state. The continuum spectrum obtained is in agreement with known experimental levels. The S-matrix contained in the NCSMC continuum wave functions of the n+10Be system is used in this work for the first time in a Transfer-to-the-Continuum (TC) reaction calculation. The TC approach is applied to study the excitation energy spectrum of 11Be measured in the 9Be(18O,16O)11Be reaction at 84 MeV. Previously known levels are confirmed and theoretical and experimental evidence for a 9/2+ state at Ex=5.8 MeV is given, whose configuration is thought to be 10Be(2+)+n(d5/2).

  • Structure of the exotic He9 nucleus from the no-core shell model with continuum
    Physical Review C, 2018
    Co-Authors: Matteo Vorabbi, Angelo Calci, Petr Navratil, Sofia Quaglioni, Michael Kruse, Guillaume Hupin
    Abstract:

    The exotic $^9$He nucleus, which presents one of the most extreme neutron-to-proton ratios, belongs to the $N=7$ isotonic chain famous for the phenomenon of ground-state Parity Inversion with decreasing number of protons. Consequently, it would be expected to have an unnatural (positive) Parity ground state similar to $^{11}$Be and $^{10}$Li. Despite many experimental and theoretical investigations, its structure remains uncertain. Apart from the fact that it is unbound, other properties including the spin and Parity of its ground state and the very existence of additional low-lying resonances are still a matter of debate. In this work we study the properties of $^9$He by analyzing the $n+^8$He continuum in the context of the ab initio no-core shell model with continuum (NCSMC) formalism with chiral interactions as the only input. The NCSMC is a state-of-the-art approach for the ab initio description of light nuclei. With its capability to predict properties of bound states, resonances, and scattering states in a unified framework, the method is particularly well suited for the study of unbound nuclei such as $^9$He. Our analysis produces an unbound $^9$He nucleus. Two resonant states are found at the energies of ${\sim}1$ and ${\sim}3.5$ MeV, respectively, above the $n+^8$He breakup threshold. The first state has a spin-Parity assignment of $J^{\pi} = {1/2}^-$ and can be associated with the ground state of $^9$He, while the second, broader state has a spin-Parity of ${3/2}^-$. No resonance is found in the ${1/2}^+$ channel, only a very weak attraction. We find that the $^9$He ground-state resonance has a negative Parity and thus breaks the Parity-Inversion mechanism found in the $^{11}$Be and $^{10}$Li nuclei of the same $N=7$ isotonic chain.

  • can ab initio theory explain the phenomenon of Parity Inversion in 11 be
    Physical Review Letters, 2016
    Co-Authors: Angelo Calci, Petr Navratil, Robert Roth, Jeremy Doheteraly, Sofia Quaglioni, Guillaume Hupin
    Abstract:

    The weakly bound exotic ^{11}Be nucleus, famous for its ground-state Parity Inversion and distinct n+^{10}Be halo structure, is investigated from first principles using chiral two- and three-nucleon forces. An explicit treatment of continuum effects is found to be indispensable. We study the sensitivity of the ^{11}Be spectrum to the details of the three-nucleon force and demonstrate that only certain chiral interactions are capable of reproducing the Parity Inversion. With such interactions, the extremely large E1 transition between the bound states is reproduced. We compare our photodisintegration calculations to conflicting experimental data and predict a distinct dip around the 3/2_{1}^{-} resonance energy. Finally, we predict low-lying 3/2^{+} and 9/2^{+} resonances that are not or not sufficiently measured in experiments.

  • Can Ab Initio Theory Explain the Phenomenon of Parity Inversion in 11-Be?
    Physical Review Letters, 2016
    Co-Authors: Angelo Calci, Petr Navratil, Robert Roth, Sofia Quaglioni, Jérémy Dohet-eraly, Guillaume Hupin
    Abstract:

    The weakly bound exotic ^{11}Be nucleus, famous for its ground-state Parity Inversion and distinct n+^{10}Be halo structure, is investigated from first principles using chiral two- and three-nucleon forces. An explicit treatment of continuum effects is found to be indispensable. We study the sensitivity of the ^{11}Be spectrum to the details of the three-nucleon force and demonstrate that only certain chiral interactions are capable of reproducing the Parity Inversion. With such interactions, the extremely large E1 transition between the bound states is reproduced. We compare our photodisintegration calculations to conflicting experimental data and predict a distinct dip around the 3/2_{1}^{-} resonance energy. Finally, we predict low-lying 3/2^{+} and 9/2^{+} resonances that are not or not sufficiently measured in experiments.

E. Vigezzi - One of the best experts on this subject based on the ideXlab platform.

  • Structure and reactions of N=7 isotones: Parity Inversion and transfer processes
    EPJ Web of Conferences, 2019
    Co-Authors: Francisco Barranco, Ricardo A. Broglia, Gregory Potel, E. Vigezzi
    Abstract:

    The interplay of particle and vibrations in N=7 isotones is considered according to nuclear field theory, focusing on the main many-body effects which renormalise the energy spectrum of the halo nucleus 11Be, leading to Parity Inversion and to renormalization of the form facto s determining the cross sections associated with one-nucleon transfer reactions.

  • The 9Li(d,p) reaction, a specific probe of 10Li, paradigm of Parity--inverted nuclei around N=6 closed shell
    arXiv: Nuclear Theory, 2018
    Co-Authors: Francisco Barranco, Gregory Potel, E. Vigezzi, R A Broglia
    Abstract:

    We show, within the framework of renormalized nuclear field theory and of the induced reaction surrogate formalism, that the highly debated $^{10}$Li structure, observed in a recent $^9$Li(d,p)$^{10}$Li one--neutron transfer experiment is consistent with or better, requires the presence of a virtual $1/2^+$ state of similar single--particle strength than that of the $1/2^-$ resonance at 0.45$\pm$ 0.03 MeV. Based on continuum spectroscopy self-energy techniques, we find that the physical mechanism responsible for Parity Inversion in $^{10}_3$Li is the same as that at the basis of the similar phenomenon observed in $^{11}_4$Be and to that needed in $^{11}$Li to have an important $s$--wave ground state component. Furthermore, it is also consistent with the (normal) sequence of the $1p_{1/2}$ and $2s_{1/2}$ levels in the $N=7$ isotones $^{12}_5$B and $^{13}_6$C.

  • one and two neutron halo at the dripline from 11be to 11li and back 10li and Parity Inversion
    arXiv: Nuclear Theory, 2018
    Co-Authors: R A Broglia, Gregory Potel, F Barranco, E. Vigezzi
    Abstract:

    The nuclei 11Be and 11Li provide paradigmatic examples of one-and two- neutron halo systems. Because the reaction 1H(11Li,9Li)3H is dominated by successive transfer, one can use the quantitative picture emerging from a nu- clear field theory description of the structure and reaction mechanism of the above Cooper pair transfer process and of the 2H(10Be,11Be)1H and 1H(11Be,10Be)2H reactions, to shed light on the structure of 10Li. This analysis provides important support for a Parity inverted scenario with a 1/2+ virtual state at about 0.2 MeV.

  • Parity Inversion breakdown of shell closure and particle vibration coupling in be isotopes
    arXiv: Nuclear Theory, 2008
    Co-Authors: G Gori, E. Vigezzi, F Barranco, R A Broglia
    Abstract:

    The properties of finite many-body systems arestrongly influenced by spatial quantization [1] leading tomarked shell structures [2]. This type of quantal sizeeffects are, on the other hand, renormalized in an impor-tant way by zero point fluctuations [3, 4]. The smallerthe system is, the largest the surface/volume ratio is andthe strongest these effects may become. In particular,the interweaving of single-particle motion and of collec-tive vibrations of the surface of atomic nuclei can leadto state dependent effective masses which, for light sys-tems can even invert the sequence of particular levels,thus altering the magic numbers associated with closedshell. While the standard parametrization of the single-particle potential [2] indicates the states 0p

  • Particle-vibration coupling in halo nuclei
    Nuclear Physics, 2005
    Co-Authors: Ricardo A. Broglia, Francisco Barranco, Pier Francesco Bortignon, Gianluca Colò, E. Vigezzi
    Abstract:

    In halo nuclei like 11 Li and 12 Be, polarization effects based on the particle-vibration coupling mechanism leads to a density dependent pairing interaction which provides most of the observed correlation energy which stabilizes the least two bound neutrons. The same mechanism is at the basis of the Parity Inversion phenomenon observed in 10 Li and 11 Be.