Remarkable optical-potential systematics for lighter heavy ions

M. E. Brandan and K. W. McVoy
Phys. Rev. C 55, 1362 – Published 1 March 1997
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Abstract

Nuclear rainbows, which appear in the elastic scattering angular distributions for certain combinations of lighter heavy ions like 12C+12C and 16O+16O, uniquely determine the major features of the optical potentials for these systems. These features are conveniently summarized by the central depth of the real part of the potential, V(r=0)100300 MeV, and by the ratio of imaginary to real parts of the potential, W(r)/V(r), found to be 1 for both small and large r (internal and far-tail transparency), but 1 in the surface region. The resulting maximum in W/V, which is found over the entire energy range 6 MeV EL/A100 MeV, appears to correlate with the peripheral reactions that occur in this energy range. At higher energies the data available indicate that the far-surface region is no longer transparent. Rather, WV there, suggesting the dominance of nuclear knockout reactions in the far tail. The knockout mode of inelasticity is the one described by the double-Glauber approximation, and W(r)V(r) agrees with the Glauber prediction in the high-energy range. This suggests that the double-Glauber prediction begins to be accurate in the low-density tail of the A1+A2 interaction around EL/A100 MeV and that its failure for the higher-density interior may provide a means of investigating the density dependence of Pauli blocking on NN scattering in the nuclear medium. By way of contrast, systems like 20Ne+12C and 14N+12C, which do not exhibit rainbows, have distinctly more absorptive potentials and do not follow the above systematics. This suggests that the imaginary part of the optical potential reflects the shell structure of the target and/or projectile in important ways, and so will not be easy to calculate from an infinite-matter many-body approach.

  • Received 22 April 1996

DOI:https://doi.org/10.1103/PhysRevC.55.1362

©1997 American Physical Society

Authors & Affiliations

M. E. Brandan

  • Instituto de Física, Universidad Nacional Autónoma de México, Apartado Postal 20-364, México 01000 Distrito Federal, Mexico

K. W. McVoy

  • Physics Department, University of Wisconsin, Madison, Wisconsin 53706

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Vol. 55, Iss. 3 — March 1997

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