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Title: Coupled-channel effects in elastic scattering and near-barrier fusion induced by weakly bound nuclei and exotic halo nuclei

Abstract

The influence on fusion of coupling to the breakup process is investigated for reactions where at least one of the colliding nuclei has a sufficiently low binding energy for breakup to become an important process. Elastic scattering, excitation functions for sub- and near-barrier fusion cross sections, and breakup yields are analyzed for {sup 6,7}Li+{sup 59}Co. Continuum-discretized coupled-channels (CDCC) calculations describe well the data at and above the barrier. Elastic scattering with {sup 6}Li (as compared to {sup 7}Li) indicates the significant role of breakup for weakly bound projectiles. A study of {sup 4,6}He induced fusion reactions with a three-body CDCC method for the {sup 6}He halo nucleus is presented. The relative importance of breakup and bound-state structure effects on total fusion is discussed.

Authors:
 [1];  [2];  [3]
  1. Institut Pluridisciplinaire Hubert Curien, UMR7178, IN2P3-CNRS et Universite Louis Pasteur (Strasbourg I), 23 rue du Loess - BP28, F-67037 Strasbourg Cedex 2 (France)
  2. DSM/DAPNIA/SPhN CEA Saclay, Orme des Merisiers, F-91191 Gif-sur-Yvette Cedex (France)
  3. Department of Nuclear Physics, Research School of Physical Sciences and Engineering, The Australian National University, Canberra ACT 0200 (Australia)
Publication Date:
OSTI Identifier:
20995291
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 75; Journal Issue: 5; Other Information: DOI: 10.1103/PhysRevC.75.054605; (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; BINDING ENERGY; BOUND STATE; COBALT 59; COUPLED CHANNEL THEORY; ELASTIC SCATTERING; EXCITATION FUNCTIONS; HEAVY ION FUSION REACTIONS; HEAVY IONS; HELIUM 6; LITHIUM 6; LITHIUM 7; MASS NUMBER; NUCLEAR HALOS; THREE-BODY PROBLEM

Citation Formats

Beck, C., Keeley, N., and Diaz-Torres, A.. Coupled-channel effects in elastic scattering and near-barrier fusion induced by weakly bound nuclei and exotic halo nuclei. United States: N. p., 2007. Web. doi:10.1103/PHYSREVC.75.054605.
Beck, C., Keeley, N., & Diaz-Torres, A.. Coupled-channel effects in elastic scattering and near-barrier fusion induced by weakly bound nuclei and exotic halo nuclei. United States. doi:10.1103/PHYSREVC.75.054605.
Beck, C., Keeley, N., and Diaz-Torres, A.. Tue . "Coupled-channel effects in elastic scattering and near-barrier fusion induced by weakly bound nuclei and exotic halo nuclei". United States. doi:10.1103/PHYSREVC.75.054605.
@article{osti_20995291,
title = {Coupled-channel effects in elastic scattering and near-barrier fusion induced by weakly bound nuclei and exotic halo nuclei},
author = {Beck, C. and Keeley, N. and Diaz-Torres, A.},
abstractNote = {The influence on fusion of coupling to the breakup process is investigated for reactions where at least one of the colliding nuclei has a sufficiently low binding energy for breakup to become an important process. Elastic scattering, excitation functions for sub- and near-barrier fusion cross sections, and breakup yields are analyzed for {sup 6,7}Li+{sup 59}Co. Continuum-discretized coupled-channels (CDCC) calculations describe well the data at and above the barrier. Elastic scattering with {sup 6}Li (as compared to {sup 7}Li) indicates the significant role of breakup for weakly bound projectiles. A study of {sup 4,6}He induced fusion reactions with a three-body CDCC method for the {sup 6}He halo nucleus is presented. The relative importance of breakup and bound-state structure effects on total fusion is discussed.},
doi = {10.1103/PHYSREVC.75.054605},
journal = {Physical Review. C, Nuclear Physics},
number = 5,
volume = 75,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}
  • The effect of breakup is investigated for the medium weight 6Li+59Co system in the vicinity of the Coulomb barrier. The strong coupling of breakup/transfer channels to fusion is discussed within a comparison of predictions of the Continuum Discretized Coupled-Channels model which is also applied to 6He+59Co a reaction induced by the borromean halo nucleus 6He.
  • The influence on the fusion process of coupling transfer/breakup channels is investigated for the medium weight {sup 6,7}Li+{sup 59}Co systems in the vicinity of the Coulomb barrier. Coupling effects are discussed within a comparison of predictions of the Continuum Discretized Coupled-Channels model. Applications to {sup 6}He+{sup 59}Co induced by the borromean halo nucleus {sup 6}He are also proposed.
  • The elastic scattering of the halo nucleus {sup 6}He from heavy targets at incident energies near the Coulomb barrier displays a marked deviation from the standard Fresnel-type diffraction behavior. This deviation is due to the strong Coulomb dipole breakup coupling produced by the Coulomb field of the heavy target, a specific feature of the nuclear structure of {sup 6}He. We have performed Continuum Discretized Coupled Channels calculations for the elastic scattering of {sup 6}He and {sup 6}Li from {sup 58}Ni, {sup 120}Sn, {sup 144}Sm, {sup 181}Ta and {sup 208}Pb targets in order to determine the range of Z{sub T} wheremore » this nuclear-structure specific coupling effect becomes manifest. We find that the strong Coulomb dipole breakup coupling effect is only clearly experimentally distinguishable for targets of Z{sub T}{approx_equal}80.« less
  • The radial sensitivity of elastic scattering for weakly bound ({sup 6}Li, {sup 7}Li, {sup 9}Be) and tightly bound projectiles ({sup 12}C, {sup 16}O) on light and heavy targets ({sup 28}Si, {sup 58}Ni, {sup 118}Sn, {sup 208}Pb, {sup 209}Bi) is sought at barrier energies, taking into account a Woods -Saxon potential and a BDM3Y1 interaction. The results are discussed in terms of the potential anomaly at the coulomb barrier.
  • It is pointed out that the usual threshold anomaly, found operative in the energy behavior of the imaginary and real parts of the optical potential representing the elastic scattering of tightly bound nuclei at near- and below-barrier energies, suffers a drastic qualitative change in the case of the elastic scattering of weakly bound projectile nuclei. Owing to the strong coupling to the breakup channel even at sub-barrier energies, the imaginary potential strength seems to increase as the energy is lowered down to below the natural, barrier, threshold, accompanied by a decrease in the real potential strength. This feature is consistentmore » with the dispersion relation. It also clearly indicates the effective increase of the barrier height. The systems 9Be, 16O + 64Zn and 6,7Li + 138Ba are analyzed to illustrate this new phenomenon.« less