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The data of inelastic 16 O+ 16 O scattering to the lowest 2 + and 3 − excited states of 16 O have been measured at E lab = 250, 350, 480, 704 and 1120 MeV and analyzed consistently in the distorted wave Born approximation (DWBA), using the semimicroscopic optical potentials and inelastic form factors given by the folding model, to reveal possible refractive structure of the nuclear rainbow that was identified earlier in the elastic 16 O+ 16 O scattering channel at the same energies. Given the known transition strengths of the 2 + 1 and 3 − 1 states of 16 O well determined from the (e, e ′ ) data, the DWBA description of the inelastic data over the whole angular range was possible only if the absorption in the exit channels is significantly increased (especially, for the 16 O+ 16 O * 2 + exit channel). Although the refractive pattern of the inelastic 16 O+ 16 O scattering was found to be less pronounced compared to that observed in the elastic scattering channel, a clear remnant of the main rainbow maximum could still be seen in the inelastic cross section at E lab = 350 − 704 MeV.

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The equation of state for cold nuclear matter is determined by the effective, density-dependent interaction between bound nucleons at temperature T = 0 . This interaction can be probed in elastic nucleus-nucleus collisions at various density overlaps which may extend to several times the normal matter density. For this purpose the elastic scattering of 16 O ions on 16 O has been measured at incident energies from 250 to 1120 MeV with high accuracy. From these data, which sample both diffractive and refractive scattering processes, we extract the underlying scattering potentials utilizing model-unrestricted analysis methods. These potentials fit very well into the systematics found in light-ion scattering and compare very favorably with microscopic calculations, if these are based on a weak density dependence of the effective NN interaction, resulting in a soft equation of state for cold nuclear matter.PACS 21.30 -Nuclear forces. PACS 21.65 -Nuclear matter. PACS 25.70.Bc -Elastic and quasielastic scattering. PACS 01.30.Cc -Conference proceedings.

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An effective nucleon-nucleon interaction calculated in nuclear matter from the Bonn potential has been parametrized in terms of a local densityand energy-dependent two-body interaction. This allows to calculate the real part of the nucleus-nucleus scattering potential and to test this effective interaction over a wide region of densities (ρ ≤ 3ρ 0 ) produced dynamically in scattering experiments. Comparing our calculations with empirical potentials extracted from data on light and heavy ion scattering by model-unrestricted analysis methods, we find quantitative agreement with the exception of proton scattering. The failure in this case may be traced back to the properties of the effective interaction at low densities, for which the nuclear matter results are not reliable. The success of the interaction at high overlap densities confirms the empirical evidence for a soft equation of state for cold nuclear matter. PACS: 21.30.+y, 21.65.+f, 25.40.Cm, 25.55.Ci, 25.70.Bc Keywords: Effective Nucleon-Nucleon Interaction, Density Dependence, Nucleus-Nucleus Scattering, Nuclear MatterThe effective interaction between nucleons bound in a nuclear medium is of fundamental interest for the understanding of nuclear structure aspects as well as of astrophysical problems like neutron stars and super nova phenomena. For the latter the behavior of the effective interaction at high densities and low temperature is crucial. In the laboratory this region is only accessible dynamically in nucleus-nucleus scattering, where the real central scattering potential is strongly affected by the density dependence of the underlying effective nucleon-nucleon (NN) interaction. In the experiment sensitivity to the real central potential is obtained by the observation of refractive scattering phenomena. Since diffractive and absorptive processes dominate the scattering process in particular for heavy scattering systems, the observation of nuclear rainbow scattering is mandatory 1 Supported by the DFG (Mu 705/3, Graduiertenkolleg) and contract F-39 11 FMSC-PAA/