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Title: Generator-Coordinate Q{sub n}-Q{sub p} Study of Low-Lying Collective States in Neutron-Rich Oxygen Isotopes

Abstract

Beyond mean-field methods based on restoration of symmetries and configuration mixing by the generator coordinate method (GCM) enable to calculate on the same footing correlations in the ground state and the properties of excited states. In this report, we generalize an analysis to allow independent neutron and proton collective dynamics. As an illustration of the method properties of the ground state and first quadrupole state in {sup 20}O are studied.

Authors:
 [1];  [2];  [3];  [4]
  1. Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, 141980 Dubna, Moscow region (Russian Federation)
  2. Universite Bordeaux 1, CNRS/IN2P3, Centre d'Etudes Nucleaires de Bordeaux Gradignan, UMR5797, Chemin du Solarium, BP120, F-33175 Gradignan (France)
  3. CNRS-IN2P3, Universite Paris XI, CSNSM, Bt. 104, F-91405 Orsay Campus (France)
  4. PNTPM, CP229, Universite Libre de Bruxelles, B-1050 Brussels (Belgium)
Publication Date:
OSTI Identifier:
21061802
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 912; Journal Issue: 1; Conference: International symposium on exotic nuclei, Khanty-Mansiysk (Russian Federation), 17-22 Jul 2006; Other Information: DOI: 10.1063/1.2746597; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; CONFIGURATION MIXING; CORRELATIONS; EXCITED STATES; GENERATOR-COORDINATE METHOD; GROUND STATES; MEAN-FIELD THEORY; NEUTRONS; NUCLEAR MODELS; NUCLEAR STRUCTURE; OXYGEN 20; PROTONS; QUADRUPOLES; SYMMETRY

Citation Formats

Severyukhin, A. P., Bender, M., Flocard, H., and Heenen, P.-H. Generator-Coordinate Q{sub n}-Q{sub p} Study of Low-Lying Collective States in Neutron-Rich Oxygen Isotopes. United States: N. p., 2007. Web. doi:10.1063/1.2746597.
Severyukhin, A. P., Bender, M., Flocard, H., & Heenen, P.-H. Generator-Coordinate Q{sub n}-Q{sub p} Study of Low-Lying Collective States in Neutron-Rich Oxygen Isotopes. United States. doi:10.1063/1.2746597.
Severyukhin, A. P., Bender, M., Flocard, H., and Heenen, P.-H. Tue . "Generator-Coordinate Q{sub n}-Q{sub p} Study of Low-Lying Collective States in Neutron-Rich Oxygen Isotopes". United States. doi:10.1063/1.2746597.
@article{osti_21061802,
title = {Generator-Coordinate Q{sub n}-Q{sub p} Study of Low-Lying Collective States in Neutron-Rich Oxygen Isotopes},
author = {Severyukhin, A. P. and Bender, M. and Flocard, H. and Heenen, P.-H.},
abstractNote = {Beyond mean-field methods based on restoration of symmetries and configuration mixing by the generator coordinate method (GCM) enable to calculate on the same footing correlations in the ground state and the properties of excited states. In this report, we generalize an analysis to allow independent neutron and proton collective dynamics. As an illustration of the method properties of the ground state and first quadrupole state in {sup 20}O are studied.},
doi = {10.1063/1.2746597},
journal = {AIP Conference Proceedings},
number = 1,
volume = 912,
place = {United States},
year = {Tue May 22 00:00:00 EDT 2007},
month = {Tue May 22 00:00:00 EDT 2007}
}
  • We present an analysis based on the generator coordinate method that allows one to disentangle the neutron and proton contributions to the properties of low-lying collective states in oxygen isotopes.
  • By means of HFB calculations with independent constraints on axial neutron and proton quadrupole moments Q{sub n} and Q{sub p}, we investigate the large amplitude isoscalar and isovector deformation properties of the neutron-rich isotope {sup 20}O. Using the particle-number and angular-momentum projected generator coordinate method, we analyze the collective dynamics in the {l_brace}<Q{sub n}>,<Q{sub p}>{r_brace} plane. The parametrization SLy4 of the Skyrme interaction is used for all calculations in connection with a density-dependent zero-range pairing interaction. Our results show that already for this moderately neutron-rich nucleus the transition moments are modified when independent neutron and proton collective dynamics are allowed.
  • Lifetime measurements of low-lying excited states in neutron-rich B and C isotopes are presented. Firstly we report on lifetime measurements of the first 2{sup +} states in {sup 16,18}C by means of the recoil-shadow method applied to a radioactive-ion beam produced at RIKEN. The observed lifetimes show suppressed collectivity of around 1 W.u. for both the isotopes. Secondly, a lifetime measurement of bound excited states in {sup 13}B with N = 8, which include the low-lying E1 state at 3.68 MeV, is discussed. The measured mean lifetime of 30(10) fs corresponds to a small E1 strength of about 1.2x10{sup -3}more » W.u., which makes a sharp contrast in strength to the large low-lying E1 strength observed in the neighboring isotone {sup 12}Be. Both results are discussed in terms of neutron-decoupling phenomena for low-lying E1 and E2 collective motion in neutron-rich nuclei.« less
  • A coupled-channel analysis of the {sup 18,20,22}O(p,p{sup '}) data has been performed to determine the neutron transition strengths of the 2{sub 1}{sup +} states in oxygen targets, using the microscopic optical potential and inelastic form factor calculated in the folding model. A complex density- and isospin-dependent version of the CDM3Y6 interaction was constructed, based on the Brueckner-Hartree-Fock calculation of nuclear matter, for the folding model input. Given an accurate isovector density dependence of the CDM3Y6 interaction, the isoscalar ({delta}{sub 0}) and isovector ({delta}{sub 1}) deformation lengths of the 2{sub 1}{sup +} states in {sup 18,20,22}O have been extracted from themore » folding model analysis of the (p,p{sup '}) data. A specific N dependence of {delta}{sub 0} and {delta}{sub 1} has been established which can be linked to the neutron shell closure occurring at N approaching 16. The strongest isovector deformation was found for the 2{sub 1}{sup +} state in {sup 20}O, with {delta}{sub 1} about 2.5 times larger than {delta}{sub 0}, which indicates a strong core polarization by the valence neutrons in {sup 20}O. The ratios of the neutron/proton transition matrix elements (M{sub n}/M{sub p}) determined for the 2{sub 1}{sup +} states in {sup 18,20}O have been compared with those deduced from the mirror symmetry, using the measured B(E2) values of the 2{sub 1}{sup +} states in the proton-rich {sup 18}Ne and {sup 20}Mg nuclei, to discuss the isospin impurity in the 2{sub 1}{sup +} excitation of the A=18, T=1 and A=20, T=2 isobars.« less