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Charge Exchange Reactions and Spin Modes

  • C. Gaarde
  • J. S. Larsen
  • J. Rapaport

Abstract

The recent (p, n) experiments at intermediate energy at the Indiana University Cyclotron1–6 have led to a major breakthrough in the understanding of spin correlations in nuclei. The (p,n) reaction for bombarding energies between 100 and 200 MeV has proven to be a unique tool for the study of spin excitations in nuclei. Fig.1 shows zero degree neutron spectra for Ep=200 MeV. 5 The spectra are seen to be dominated by a single peak which is interpreted as a collective l+-state, the giant Gamow-Teller state, the isospin-spin nuclear sound. The collective state carries a large fraction of the total Gamow-Teller strength, i.e. strength associated with the operator σμt_ that governs Gamow-Teller β-decay. The concentration of strength into a collective state was first discussed by K. Ikeda, S. Fujii and J.I. Fujita as early as 1963.7 In a shell model picture of e.g. 208Pb the G.T. operator has non-zero matrix elements with all 44 excess neutrons (and the 12 h11/2 neutrons in the next lower shell). The collective state then corresponds to a transition where all these nucleons coherently change direction of spin and isospin.

Keywords

Heavy Nucleus Neutron Spectrum Symmetry Energy Collective State Total Strength 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Plenum Press, New York 1984

Authors and Affiliations

  • C. Gaarde
    • 1
  • J. S. Larsen
    • 1
  • J. Rapaport
    • 1
  1. 1.Niels Bohr InstituteUniversity of CopenhagenCopenhagenDenmark

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