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An optical-model analysis of 12 C + 12 C elastic scattering from E^n^ = 35 to 63 MeV indicates a sensitivity of the scattering cross section at large scattering angles (0 C m ~50"' -90°) to a region of internuclear separation extending in to r~2 fm. Real nuclear potentials obtained with the folding model and a realistic interaction fit the data remarkably well. This suggests that the nuclear potential for 12 C + 12 C in the region of large overlap is significantly deeper than would be expected on the basis of previous analyses of systems such as 16 0 + 16 0.The subjects of heavy-ion elastic scattering measurements and the shape and depth of the real nucleus-nucleus potential have received considerable study during the past decade. 1 The present work bears on two important features of heavyion reactions which have emerged during this period. First, in systems with rj < 10 (rf = Z 1 Z 2 e 2 /Hv) it has been seen that the elastic scattering is sensitive to the value of the real potential only over a narrow region of internucleus separation centered at the strong-absorption radius. 2 * 3 Second, an analysis of the scattering of ie O + 16 0 at energies £ c#nu ^40 MeV (77 >4.6) led to the introduction of very shallow Woods-Saxon real potentials (F~-17MeV, r 0~1 .35fm, a-0.56 fm) 4 ' 5 which were then used to fit a variety of other heavy-ion systems, 12 C + 12 C included, at comparable bombarding energies. 6 In our analysis of 12 C + 12 C elastic scattering at energies from £ c>m =35 to 63 MeV (r] = 2.4-1.8), we find a marked sensitivity of the scattering to the value of the real potential over the large region r^ 2-8 fm. Most remarkably, the real potential in the interior region deduced for 12 C + 12 C appears to be much deeper than was found earlier 4 for the 16 0 + 16 0 system. In fact, it is the "deep" potentials predicted by the double-folding model 2 with a realistic interaction 7,8 which are successful in reproducing the 12 C+ 12 C elastic scattering.The experimental data were obtained at the Oak Ridge isochronous cyclotron facility and consist of angular distributions measured at fourteen bombarding energies. 9 They will be described in detail in a separate publication. Figure 1 shows representative angular distributions at six of these energies. The high bombarding energies minimized contributions from compound elastic scattering 10 such that an analysis of individual angular distributions (as opposed to energy-averaged excitation functions) was possible. The optical-model codefflGENOA 11 was used with real potentials either of the Woods-Saxon type or from the folding model. In both cases, the imaginary potentials were Woods-Saxon. Regardless of the type of real potential, we found that the best fits to the data required an imaginary potential with a central depth in the range of 10-20 MeV.The absorptive strength given by the above imaginary potential (corresponding to a mean free path of about 2 fm), together with the small values of 77, accounts for the dependence of the predicted angular distributions on the...

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