The soft Giant Monopole Resonance as a probe of the spin-orbit splitting

Yüksel, Esra; Khan, E.; Bozkurt, Kutsal

doi:10.1140/epja/i2013-13124-6

Cited by 9 publications

(9 citation statements)

References 28 publications

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“…In addition, a soft monopole mode has been predicted around 14 MeV in neutron-rich nuclei by several relativistic and nonrelativistic models [13][14][15], but it has never been observed, due to the difficulty in measuring the monopole response in nuclei far from stability. The soft monopole mode is predicted to be noncollective and its observation could bring valuable information on spin-orbit splitting [16]. It is therefore essential to measure the isoscalar (in-phase motion of protons and neutrons) monopole response in neutron-rich nuclei.…”

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confidence: 99%

Publisher’s Note: Measurement of the Isoscalar Monopole Rsponse in the Neutron-Rich NucleusNi68[Phys. Rev. Lett. 113, 032504 (2014)]

Vandebrouck¹,

Gibelin²,

Khan³

et al. 2014

Phys. Rev. Lett.

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The isoscalar monopole response has been measured in the unstable nucleus 68 Ni using inelastic alpha scattering at 50A MeV in inverse kinematics with the active target MAYA at GANIL. The isoscalar giant monopole resonance (ISGMR) centroid was determined to be 21.1 AE 1.9 MeV and indications for a soft monopole mode are provided for the first time at 12.9 AE 1.0 MeV. Analysis of the corresponding angular distributions using distorted-wave-born approximation with random-phase approximation transition densities indicates that the L ¼ 0 multipolarity dominates the cross section for the ISGMR and significantly contributes to the low-energy mode. The L ¼ 0 part of this low-energy mode, the soft monopole mode, is dominated by neutron excitations. This demonstrates the relevance of inelastic alpha scattering in inverse kinematics in order to probe both the ISGMR and isoscalar soft modes in neutron-rich nuclei.

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confidence: 99%

Publisher’s Note: Measurement of the Isoscalar Monopole Rsponse in the Neutron-Rich NucleusNi68[Phys. Rev. Lett. 113, 032504 (2014)]

Vandebrouck¹,

Gibelin²,

Khan³

et al. 2014

Phys. Rev. Lett.

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“…To understand the origin of the low-energy monopole collectivity, let us analyze the wave-function structure of these states. The first one-phonon RPA state appears above 11.5 MeV [21]. The extension of the variational space from the standard RPA to include the two-phonon configurations has a strong effect on the low-energy 0 + spectrum of 132 Sn.…”

Section: Resultsmentioning

confidence: 97%

“…A complete list of references on that subject is given in [12]. On the theoretical side, the standard tools for ISGMR studies are random phase approximation (RPA) and quasiparticle RPA (QRPA) in the case of open-shell nuclei in which the self-consistent mean-field is derived from effective nucleon-nucleon interactions that are taken as nonrelativistic twobody Skyrme [13][14][15][16][17][18][19][20][21][22][23] or Gogny [15,[24][25][26] forces. They are also derived from relativistic Lagrangians, e.g., [17,22,[27][28][29].…”

Section: Introductionmentioning

confidence: 99%

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Origin of Low- and High-Energy Monopole Collectivity in 132Sn

Arsenyev

Severyukhin

2021

Universe

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Beginning with the Skyrme interaction, we study the properties of the isoscalar giant monopole resonances (ISGMR) of 132Sn. Using the finite-rank separable approximation for the particle-hole interaction, the coupling between one- and two-phonon terms in the wave functions of excited states is taken into account in very large configurational spaces. The inclusion of the phonon–phonon coupling (PPC) results in the formation of a low-energy 0+ state. The PPC inclusion leads to a fragmentation of the ISGMR strength to lower energy states and also to a higher energy tail. Using the same set of parameters, we describe the available experimental data for the ISGMR characteristics of 118,120,122,124Sn and give a prediction for 126,128,130,132Sn.

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“…Namely, in such cases, one observes a redistribution of the strength functions towards lower energy, below the GRs, associated with the emergence of new, exotic patterns of excitation [1][2][3]. The nature of these new excitations is basically twofold, namely (i) so-called soft modes involving resonant oscillations of a neutron skin against a tightly bound core [4][5][6][7], or nonresonant individual excitations [8,9] and (ii) cluster vibrations [10][11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

Low-energy monopole strength in spherical and deformed nuclei : cluster and soft modes

Mercier,

Ebran,

Khan

2021

Preprint

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Background: Several recent experiments report significant low-energy isoscalar monopole strength, below the giant resonance, in various nuclei. In light α-conjugate nuclei, these low-energy resonances were recently interpreted as cluster vibration modes. However, the nature of these excitations in neutron-rich nuclei remain elusive. Purpose:The present work provides a systematic analysis of the low-energy monopole strength in isotopic chains, from Neon to Germanium, in order to monitor and understand its nature and conditions of emergence.Methods: We perform covariant quasiparticle random phase approximation (QRPA) calculations, formulated within the finite amplitude method (FAM), on top of constrained relativistic Hartree-Bogoliubov (RHB) reference states.Results: Neutron excess leads to the appearance of low-energy excitations according to a systematic pattern reflecting the single-particle features of the underlying RHB reference state. With the onset of deformation, these low-energy resonances get split and give rise to more complex patterns, with possible mixing with the giant resonance. At lower energy, cluster-like excitations found in N = Z systems survive in neutron-rich nuclei, with valence neutrons arranging in molecular-like orbitals. Finally, at very low energy, pair excitations are also found in superfluid nuclei, but remain negligible in most of the cases. Conclusions:The low-energy part of the monopole strength exhibits various modes, from cluster vibrations (∼ 5-10 MeV) to components of the giant resonance downshifted by the onset of deformation, including soft modes (∼ 10-15 MeV) as well as pair excitation (< 5 MeV), with possible mixing, depending on neutron-excess, deformation, and pairing energy.

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The soft Giant Monopole Resonance as a probe of the spin-orbit splitting

Cited by 9 publications

References 28 publications

Publisher’s Note: Measurement of the Isoscalar Monopole Rsponse in the Neutron-Rich NucleusNi68[Phys. Rev. Lett. 113, 032504 (2014)]

Publisher’s Note: Measurement of the Isoscalar Monopole Rsponse in the Neutron-Rich NucleusNi68[Phys. Rev. Lett. 113, 032504 (2014)]

Origin of Low- and High-Energy Monopole Collectivity in 132Sn

Low-energy monopole strength in spherical and deformed nuclei : cluster and soft modes

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