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Title: Threshold effects in multichannel coupling and spectroscopic factors in exotic nuclei

Abstract

In the threshold region, the cross section and the associated overlap integral obey the Wigner threshold law that results in the Wigner-cusp phenomenon. Due to flux conservation, a cusp anomaly in one channel manifests itself in other open channels, even if their respective thresholds appear at a different energy. The shape of a threshold cusp depends on the orbital angular momentum of a scattered particle; hence, studies of Wigner anomalies in weakly bound nuclei with several low-lying thresholds can provide valuable spectroscopic information. In this work, we investigate the threshold behavior of spectroscopic factors in neutron-rich drip-line nuclei using the Gamow shell model, which takes into account many-body correlations and the continuum effects. The presence of threshold anomalies is demonstrated and the implications for spectroscopic factors are discussed.

Authors:
 [1];  [2];  [2];  [1];  [2];  [3];  [4]
  1. Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996 (United States)
  2. (United States)
  3. (Poland)
  4. Grand Accelerateur National d'Ions Lourds (GANIL), CEA/DSM-CNRS/IN2P3, BP 55027, F-14076 Caen Cedex (France)
Publication Date:
OSTI Identifier:
20995105
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 75; Journal Issue: 3; Other Information: DOI: 10.1103/PhysRevC.75.031301; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; COUPLING; CROSS SECTIONS; CUSPED GEOMETRIES; MANY-BODY PROBLEM; NEUTRONS; NUCLEI; ORBITAL ANGULAR MOMENTUM; SHELL MODELS; SPECTROSCOPIC FACTORS

Citation Formats

Michel, N., Physics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831, Joint Institute for Heavy Ion Research, Oak Ridge, Tennessee 37831, Nazarewicz, W., Physics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831, Institute of Theoretical Physics, Warsaw University, ul. Hoza 69, PL-00-681 Warsaw, and Ploszajczak, M. Threshold effects in multichannel coupling and spectroscopic factors in exotic nuclei. United States: N. p., 2007. Web. doi:10.1103/PHYSREVC.75.031301.
Michel, N., Physics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831, Joint Institute for Heavy Ion Research, Oak Ridge, Tennessee 37831, Nazarewicz, W., Physics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831, Institute of Theoretical Physics, Warsaw University, ul. Hoza 69, PL-00-681 Warsaw, & Ploszajczak, M. Threshold effects in multichannel coupling and spectroscopic factors in exotic nuclei. United States. doi:10.1103/PHYSREVC.75.031301.
Michel, N., Physics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831, Joint Institute for Heavy Ion Research, Oak Ridge, Tennessee 37831, Nazarewicz, W., Physics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831, Institute of Theoretical Physics, Warsaw University, ul. Hoza 69, PL-00-681 Warsaw, and Ploszajczak, M. Thu . "Threshold effects in multichannel coupling and spectroscopic factors in exotic nuclei". United States. doi:10.1103/PHYSREVC.75.031301.
@article{osti_20995105,
title = {Threshold effects in multichannel coupling and spectroscopic factors in exotic nuclei},
author = {Michel, N. and Physics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831 and Joint Institute for Heavy Ion Research, Oak Ridge, Tennessee 37831 and Nazarewicz, W. and Physics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831 and Institute of Theoretical Physics, Warsaw University, ul. Hoza 69, PL-00-681 Warsaw and Ploszajczak, M.},
abstractNote = {In the threshold region, the cross section and the associated overlap integral obey the Wigner threshold law that results in the Wigner-cusp phenomenon. Due to flux conservation, a cusp anomaly in one channel manifests itself in other open channels, even if their respective thresholds appear at a different energy. The shape of a threshold cusp depends on the orbital angular momentum of a scattered particle; hence, studies of Wigner anomalies in weakly bound nuclei with several low-lying thresholds can provide valuable spectroscopic information. In this work, we investigate the threshold behavior of spectroscopic factors in neutron-rich drip-line nuclei using the Gamow shell model, which takes into account many-body correlations and the continuum effects. The presence of threshold anomalies is demonstrated and the implications for spectroscopic factors are discussed.},
doi = {10.1103/PHYSREVC.75.031301},
journal = {Physical Review. C, Nuclear Physics},
number = 3,
volume = 75,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}
  • Fast beams of radioactive isotope (RI) have been used for nuclear spectroscopy at RIKEN since 1990. Various direct-reaction experiments have been performed at intermediate-energies in the reversed kinematics to study structures of nuclei very far from the stability valley. Several examples of recent results on neutron-rich nuclei around N=20 and carbon isotopes are presented. The RIKEN RI Beam Factory, which will have the first beam in the end of 2006, will greatly extend the region of study to more exotic and heavier nuclei.
  • How to identify the orbital of the valence nucleon(s) of exotic nuclei is an important problem. The elastic magnetic electron scattering is an excellent probe to determine the valence structure of odd-A nuclei. The relativistic mean-field theory has been successfully applied to systematic studies of the elastic charge electron scattering from even-even exotic nuclei. The extension of this method to investigate the elastic magnetic electron scattering from odd-A exotic nuclei is a natural generalization. The experimental form factors of {sup 17}O and {sup 41}Ca are reproduced very well with the help of the spectroscopic factors which are introduced into themore » relativistic treatment of the magnetic electron scattering for the first time. The emphases are put on the magnetic form factors of {sup 15,17,19}C, {sup 23}O, {sup 17}F, and {sup 49,59}Ca calculated in the relativistic impulse approximation. Great differences have been found in the form factors of the same nucleus with different configurations. Therefore, the elastic magnetic electron scattering can be used to determine the orbital of the last nucleon of odd-A exotic nuclei. Our results can provide references for the electron scattering from exotic nuclei in the near future.« less
  • Elastic and inelastic electron scattering form factors for several neutron-rich exotic nuclei are presented. The results have been obtained using large space no-core shell models. While the elastic scattering form factors are insensitive to the details of the neutron density, it is found that inelastic scattering may be influenced by extensive neutron distributions.
  • We study the properties of light neutron-rich exotic nuclei with relativistic-mean-field models. The nonlinear isoscalar-isovector term that is not constrained by the present data is considered. The {rho}NN tensor coupling is included. The data-to-data correlation between the neutron radius of {sup 208}Pb and that of light exotic oxygen, fluorine, and neon isotopes is enhanced by the inclusion of the {rho}NN tensor coupling subject to the 2s{sub 1/2} occupation of the outlayer neutrons. This enhancement is determined by the single-particle property rather than by the bulk-matter property. The role of the {rho}NN tensor coupling and the pairing correlation in reducing themore » model dependence of the neutron thickness in light exotic nuclei is investigated. The influence of the isoscalar-isovector term on halo neutrons, characteristic of the 2s{sub 1/2} occupation, is discussed.« less