Remarkable optical-potential systematics for lighter heavy ions
- Instituto de Fisica, Universidad Nacional Autonoma de Mexico, Apartado Postal 20-364, Mexico 01000 Distrito Federal (Mexico)
- Physics Department, University of Wisconsin, Madison, Wisconsin 53706 (United States)
Nuclear rainbows, which appear in the elastic scattering angular distributions for certain combinations of lighter heavy ions like {sup 12}C+{sup 12}C and {sup 16}O+{sup 16}O, 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){approximately}100{minus}300 MeV, and by the ratio of imaginary to real parts of the potential, W(r)/V(r), found to be {lt}1 for both small and large r (internal and far-tail transparency), but {approx}1 in the surface region. The resulting maximum in W/V, which is found over the entire energy range 6 MeV {approx_lt}E{sub L}/A{approx_lt}100 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, W{approx}V 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){approx}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 A{sub 1}+A{sub 2} interaction around E{sub L}/A{approx}100 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 {sup 20}Ne+{sup 12}C and {sup 14}N+{sup 12}C, 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. {copyright} {ital 1996} {ital The American Physical Society}
- OSTI ID:
- 524961
- Journal Information:
- Physical Review, C, Vol. 55, Issue 3; Other Information: PBD: Mar 1997
- Country of Publication:
- United States
- Language:
- English
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