Emergence of a secondary rainbow and the dynamical polarization potential for O16 on C12 at 330 MeV

R. S. Mackintosh, Y. Hirabayashi, and S. Ohkubo
Phys. Rev. C 91, 024616 – Published 23 February 2015

Abstract

Background: It was shown recently that an anomaly in the elastic scattering of O16 on C12 at around 300 MeV is resolved by including within the scattering model the inelastic excitation of specific collective excitations of both nuclei, leading to a secondary rainbow. There is very little systematic knowledge concerning the contribution of collective excitations to the interaction between nuclei, particularly in the overlap region when neither interacting nuclei are light nuclei.

Purpose: Our goals are to study the dynamic polarization potential (DPP) generated by channel coupling that has been experimentally validated for a case (O16 on C12 at around 300 MeV) where scattering is sensitive to the nuclear potential over a wide radial range; to exhibit evidence of the nonlocality due to collective coupling; to validate, or otherwise invalidate, the representation of the DPP by uniform renormalizing folding models or global potentials.

Methods: S-matrix to potential, SLV(r), inversion yields local potentials that reproduce the elastic channel S matrix of coupled channel calculations. Subtracting the elastic channel uncoupled potential yields a local L-independent representation of the DPP. The dependence of the DPP on the nature of the coupled states and other parameters can be studied.

Results: Local DPPs were found due to the excitation of C12 and the combined excitation of O16 and C12. The radial forms were different for the two cases, but each were very different from a uniform renormalization of the potential. The full coupling led to a 10% increase in the volume integral of the real potential. Evidence for the nonlocality of the underlying formal DPP and for the effect of direct coupling between the collective states is presented.

Conclusions: The local DPP generating the secondary rainbow has been identified. In general, DPPs have forms that depend on the nature of the specific excitations generating them, but, as in this case, they cannot be represented by a uniform renormalization of a global model or folding model potential. The method employed herein is a useful tool for further exploration of the contribution of collective excitations to internuclear potentials, concerning which there is still remarkably little general information.

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  • Received 23 December 2014
  • Revised 28 January 2015

DOI:https://doi.org/10.1103/PhysRevC.91.024616

©2015 American Physical Society

Authors & Affiliations

R. S. Mackintosh*

  • Department of Physical Sciences, The Open University, Milton Keynes MK7 6AA, United Kingdom

Y. Hirabayashi

  • Information Initiative Center, Hokkaido University, Sapporo 060-0811, Japan

S. Ohkubo

  • Research Center for Nuclear Physics, Osaka University, Ibaraki, Osaka 567-0047, Japan and University of Kochi, Kochi 780-8515, Japan

  • *raymond.mackintosh@open.ac.uk
  • hirabay@iic.hokudai.ac.jp
  • ohkubo@yukawa.kyoto-u.ac.jp

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Issue

Vol. 91, Iss. 2 — February 2015

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