Pygmy resonances: what's in a name?
Broglia, Ricardo ; Barranco, Francisco ; Idini, Andrea LU
; Potel, Gregory
and Vigezzi, Enrico
(2019)
In Physica Scripta
94(11).
- Abstract
- The centroid, width and percentage of energy weighted sum rule of dipole resonances can be strongly affected by dynamical fluctuations and static deformations of the nuclear surface, deformations and fluctuations which, in turn, depend on pairing, and thus on Cooper pairs. Because of angular momentum conservation, such insight is restricted, to lowest order, to fluctuations/deformations of quadrupole and monopole type. The latter being closely connected with the neutron (excess) skin and thus with soft dipole modes. From the values (N − Z)/A ≈ 0.18, 0.21, and 0.45 for the nuclei 122Sn, 208Pb, and 11Li, it is expected that the latter system, which is weakly bound by pairing effects (spatially extended single Cooper pair and odd proton... (More)
- The centroid, width and percentage of energy weighted sum rule of dipole resonances can be strongly affected by dynamical fluctuations and static deformations of the nuclear surface, deformations and fluctuations which, in turn, depend on pairing, and thus on Cooper pairs. Because of angular momentum conservation, such insight is restricted, to lowest order, to fluctuations/deformations of quadrupole and monopole type. The latter being closely connected with the neutron (excess) skin and thus with soft dipole modes. From the values (N − Z)/A ≈ 0.18, 0.21, and 0.45 for the nuclei 122Sn, 208Pb, and 11Li, it is expected that the latter system, which is weakly bound by pairing effects (spatially extended single Cooper pair and odd proton acting as spectator), constitutes an attractive laboratory to study the properties of soft E1-modes and thus of isospin nuclear deformation. From the calculation of the full dipole response function in QRPA, discretizing the continuum in a spherical box of radius of 40 fm, one finds a GDR with centroid E x ≈ 24 MeV, width Γ ≈11 MeV and carrying 90% of the EWSR, and a low-lying collective resonance characterized by E X = 0.75 MeV, Γ = 0.5 MeV and 6.2% EWSR. The wave function of the latter resonance is built out of about fifteen components (both protons and neutrons), typical of a collective mode. The transition densities indicate this soft E1-mode to be generated by surface density oscillation of the neutron (halo) skin (Δr np ≈ 1.71 fm) relative to an approximately isospin-saturated core. Through a detailed study of the full dipole response of 11Li we will draw a comparison between the soft E1-mode of this halo nucleus and the PDR of heavy stable nuclei, pointing to the physical similarities and also to the basic differences. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/44b61849-ebf8-43ec-aea0-77cf4b7357d1
- author
- Broglia, Ricardo
; Barranco, Francisco
; Idini, Andrea
LU
; Potel, Gregory
and Vigezzi, Enrico
- organization
- publishing date
- 2019
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Physica Scripta
- volume
- 94
- issue
- 11
- article number
- 114002
- publisher
- IOP Publishing
- external identifiers
-
- scopus:85074603503
- ISSN
- 0031-8949
- DOI
- 10.1088/1402-4896/ab2431
- language
- English
- LU publication?
- yes
- id
- 44b61849-ebf8-43ec-aea0-77cf4b7357d1
- date added to LUP
- 2019-05-20 14:04:49
- date last changed
- 2025-04-04 14:55:22
@article{44b61849-ebf8-43ec-aea0-77cf4b7357d1,
abstract = {{The centroid, width and percentage of energy weighted sum rule of dipole resonances can be strongly affected by dynamical fluctuations and static deformations of the nuclear surface, deformations and fluctuations which, in turn, depend on pairing, and thus on Cooper pairs. Because of angular momentum conservation, such insight is restricted, to lowest order, to fluctuations/deformations of quadrupole and monopole type. The latter being closely connected with the neutron (excess) skin and thus with soft dipole modes. From the values (N − Z)/A ≈ 0.18, 0.21, and 0.45 for the nuclei 122Sn, 208Pb, and 11Li, it is expected that the latter system, which is weakly bound by pairing effects (spatially extended single Cooper pair and odd proton acting as spectator), constitutes an attractive laboratory to study the properties of soft E1-modes and thus of isospin nuclear deformation. From the calculation of the full dipole response function in QRPA, discretizing the continuum in a spherical box of radius of 40 fm, one finds a GDR with centroid E x ≈ 24 MeV, width Γ ≈11 MeV and carrying 90% of the EWSR, and a low-lying collective resonance characterized by E X = 0.75 MeV, Γ = 0.5 MeV and 6.2% EWSR. The wave function of the latter resonance is built out of about fifteen components (both protons and neutrons), typical of a collective mode. The transition densities indicate this soft E1-mode to be generated by surface density oscillation of the neutron (halo) skin (Δr np ≈ 1.71 fm) relative to an approximately isospin-saturated core. Through a detailed study of the full dipole response of 11Li we will draw a comparison between the soft E1-mode of this halo nucleus and the PDR of heavy stable nuclei, pointing to the physical similarities and also to the basic differences.}},
author = {{Broglia, Ricardo and Barranco, Francisco and Idini, Andrea and Potel, Gregory and Vigezzi, Enrico}},
issn = {{0031-8949}},
language = {{eng}},
number = {{11}},
publisher = {{IOP Publishing}},
series = {{Physica Scripta}},
title = {{Pygmy resonances: what's in a name?}},
url = {{http://dx.doi.org/10.1088/1402-4896/ab2431}},
doi = {{10.1088/1402-4896/ab2431}},
volume = {{94}},
year = {{2019}},
}